Bulletin of the American Physical Society
41st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 55, Number 5
Tuesday–Saturday, May 25–29, 2010; Houston, Texas
Session T1: Poster Session III (4:00 pm - 6:00 pm) |
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Room: Exhibit Hall |
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T1.00001: QUANTUM AND/OR NONLINEAR OPTICS |
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T1.00002: Spectral narrowing induced by discrete frequency fluctuations Yoav Sagi, Rami Pugatch, Ido Almog, Nir Davidson We study an ensemble of two level systems coupled to an environment that randomly modulates their resonant frequency. We use Poissonian statistics for the random frequency jumps and derive a closed-from formula for the spectrum in terms of the inhomogeneous frequency distribution and the Poisson rate constant. We show that for a Gaussian distribution our result asymptotically reproduces the results of the well known Kubo model. Our formula holds for any frequency distribution. In particular we calculate the spectrum of atoms in a 3D trap harmonic trap and show that motional narrowing naturally emerges. We experimentally measure this spectrum with optically trapped $^{87}Rb$ atoms and obtain a good agreement to our theory without fitting parameters. Our theory apply to a wide range of systems such as atomic ensembles, nuclear magnetic resonance spectroscopy, single molecule spectroscopy and the line-shape of lasers. [Preview Abstract] |
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T1.00003: Study of forward and diffusely scattered light in ultracold $^{87}$Rb under EIT conditions R.G. Olave, A.L. Win, M.D. Havey, I.M. Sokolov, D.V. Kupriyanov We report a combined experimental and theoretical study of light propagation in ultracold atomic $^{87}Rb$ vapor under conditions of electromagnetically induced transparency. The main focus is comparison of time-resolved polarized light scattering in forward and in sideways directions. To this end, we use a lambda configuration on the $F = 1 \to F' = 2 \to F = 2$ components of the D2 line. Experiments are performed on an ultracold gas sample having a characteristic temperature of 100 $\mu K$ and typical peak optical depth $b \sim 10$. We observe slowed propagation of forward scattered light, and formation and retrieval of dark state polaritons under a variety of conditions. In the fluorescence geometry we observe behavior complementary to the forward scattering case, and influence, on the time evolution of the scattered light, of the dressing of the atomic medium by the control field. Comprehensive and realistic theoretical treatment of the process is made and compares favorably with the experimental results. [Preview Abstract] |
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T1.00004: Studies of Negative Refraction Without Absorption Renuka Rajapakse, Susanne Yelin We study suitable systems for negative refractive index with minimal absorption. We suggest a modified level scheme of atoms, excitons or polar molecules to study negative refractive index without absorption. Quantum interference effects to suppress absorption and introduce negative refraction are discussed. The main limitations in systems introduced so far are the necessity of resonant electric and magnetic dipole transitions, and the necessity of very dense media. We suggest using four wave mixing and using a 'black box' system that would provide negative refraction for a range of optical frequencies while attempting to overcome the limitations discussed above. [Preview Abstract] |
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T1.00005: Propagation of quantized fields through negative-index media Martin Ligare Materials in which both the relative permittivity $\epsilon$ and the relative permeability $\mu$ are negative exhibit striking optical properties, many of which are the consequence of the fact that the effective index of refraction in these media is negative. Most studies of the propagation of electromagnetic fields in these media have concentrated on classical fields. In contrast, I use simple fully-quantized models to illustrate how some of the striking properties of negative-index media are manifested in the propagation of single photons. The photons in these models originate in the spontaneous emission of idealized two-level atoms, and I follow the spatial and temporal evolution of the intensity expectation value as the field propagates across vacuum-dielectric interfaces and through negative-index media. I also calculate the time-dependent excitation of atoms used as field detectors. The results illustrate the one-photon quantum analogs of the classical group velocity, the classical phase velocity (directed opposite to the direction of propagation), and the focusing properties of negative-index slabs. [Preview Abstract] |
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T1.00006: Nonlinear Optics with an Atomic Ytterbium Vapor K.R. Moore, E.A. Alden, A.E. Leanhardt A theoretical analysis of two-photon cascade emission and four- wave mixing in a three-level atomic system is presented. The specific levels of interest are the $^1$S$_0$, $^3$P$_1$, and $^3$D$_2$ states in atomic ytterbium. Cascade emission along the decay path $^3$D$_2$ $\rightarrow$ $^3$P$_1$ $\rightarrow$ $^1$S$_0$ generates photons at 1479 nm and 556 nm, respectively. For various emission directions, this decay sequence can produce either (i) polarization-entangled photon pairs or (ii) entanglement between the polarization of one of the emitted photons and the Yb nuclear spin. Finally, simultaneous excitation of the $^1$S$_0$ $\rightarrow$ $^3$D$_2 $ two-photon transition (808 nm) and the $^1$S$_0$ $\rightarrow$ $^3$P$_1$ single-photon transition (556 nm) can be used to generate a 1479 nm radiation field (resonant with the $^3$D$_2$ $\rightarrow$ $^3$P$_1$ transition) through four- wave mixing. Experimental progress towards observing these processes will be presented. [Preview Abstract] |
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T1.00007: Lambda system interacting with one cw and one modulated optical beam James Supplee, Edward A. Whittaker We are using a semiclassical model to calculate the response of a lambda system to two optical beams, each near resonance with an allowed transition. One beam is modeled as a steady cw beam, while the other is frequency and/or amplitude modulated. We are interested in understanding how the response of the system is affected by various parameters, including the detuning of each beam from resonance and the strength and frequency of the modulations. It is interesting to consider which parameter regimes can be understood more intuitively in the time-domain and which in the frequency-domain. This progress report may touch briefly on the conditions for coherent population trapping, and the conditions for the appearance of Ramsey-like fringes. [Preview Abstract] |
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T1.00008: Probe spectrum of alkali atoms in a weakly driven two mode cavity James Clemens We calculate the probe spectrum for alkali atoms in a damped, weakly driven cavity supporting two degenerate orthogonally polarized modes. One mode is weakly driven by a linearly polarized external field. The atoms, initially prepared in a single hyperfine ground state, couple to the driven mode as well as the orthogonally polarized mode by making transitions to other hyperfine sublevels. We compare probe spectra for three- and four-level models. In both cases the spectrum for the driven mode is a vacuum Rabi doublet familiar from the driven, damped Jaynes-Cummings model. The undriven mode spectrum is a triplet with the maximum on resonance for the three level model while the four level model has a four peaked spectrum. We discuss the role of strong coupling to the undriven mode in accounting for the qualitative difference between the models. [Preview Abstract] |
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T1.00009: Phase-Sensitive Amplification by Four-Wave Mixing in an Atomic Vapor Neil Corzo, Alberto Marino, Jeremy Clark, Andrew Lance, Kevin Jones, Paul Lett A phase-sensitive amplifier (PSA) is based on a parametric process that can amplify or deamplify a signal depending on the phase of the input. It does so without degrading the signal to noise ratio of the input, contrary to a phase-insensitive amplifier (PIA) which adds at least 3dB of noise to the signal in the limit of high gain. This makes it possible to obtain noiseless amplification of a signal, making it a key element in optical communication systems. For the particular case where the input signal's phase is chosen for maximum deamplification the PSA can generate squeezed light. We present an experimental realization of a phase-sensitive optical amplifier using a four-wave mixing interaction based on a double-lambda configuration in hot Rb vapor. We report nearly noiseless amplification for a range of gains as well as the generation of ``single-beam'' squeezing. We compare the results obtained with a theorical phase-insensitive scheme. The lack of a cavity in our system and relaxed phase-matching conditions can be used to observe noiseless amplification of multi-spatial-mode signals (i.e. images). [Preview Abstract] |
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T1.00010: Towards quantum imaging with multi-spatial mode quantum-correlated twin-beams Jeremy Clark, Andrew Lance, Neil Corzo, Alberto Marino, Kevin Jones, Paul Lett Quantum optical properties of multi-spatial mode light fields allow for a variety of multichannel quantum information applications including quantum imaging. We have constructed a new apparatus capable of generating pulsed quantum correlated twin-beams via a four-wave mixing process in a hot rubidium vapor. We report temporal intensity-difference squeezing in both the continuous-wave and pulsed regimes with pulse durations as short as one microsecond. Such temporal squeezing measurements, however, typically involve focusing the entirety of each beam onto a pair of balanced photodetectors and therefore fail to resolve spatial characteristics of the light. We aim to extend the analysis of our system into the spatial domain by imaging these bright twin-beams onto a CCD camera and performing image registration in order to demonstrate sub-shot-noise spatial correlations over the ensemble of corresponding coherence areas in each beam. Ultimately, our objective is to use such an apparatus to demonstrate quantum-enhanced imaging techniques that benefit from the use of several spatial modes. [Preview Abstract] |
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T1.00011: Vibrational and Rotational Raman Stokes Generation in a High Finesse Cavity Jonathan Green, Deniz Yavuz We demonstrate the generation of continuous wave Stokes beams for both rotational and vibrational transitions in Deuterium gas. We report the generation of more than 300mW of rotational Stokes output power in molecular Deuterium which, to our knowledge, is the largest output power generated in a high finesse cavity-based continuous Raman laser. These experiments are carried out at a gas pressure of 0.1 atm, which is about 2 orders of magnitude lower than the pressure used in previous experiments. [Preview Abstract] |
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T1.00012: Novel cooperative effects in dipolar media Susanne Yelin, Elena Kuznetsova Recent developments in formalism and application of superradiance are discussed. We present cooperative effects in novel systems such as nuclear spins in diamond NV centers or quantum dots and in novel applications such as cooling/manipulation of vibrational decay in ultracold molecules. [Preview Abstract] |
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T1.00013: Real-Time Cavity QED with Single Atoms and a Microtoroidal Resonator N.P. Stern, D.J. Alton, H. Lee, K.J. Vahala, H.J. Kimble Strong coupling in cavity quantum electrodynamics (cQED) with atoms and microtoroid resonators allows coherent interactions between matter and light to dominate irreversible dissipation in a scalable quantum node with high photonic coupling efficiency.\footnote{T. Aoki, \textit{et al.}, \textit{Nature} \textbf{443}, 671 (2006).} Previous microtoroid cQED experiments use post-selection of atom transits from the photon record,\footnote{B. Dayan, \textit{et al.}, \textit{Science} \textbf{319}, 1062 (2008).}$^,$\footnote{T. Aoki, \textit{et al.}, \textit{Phys. Rev. Lett.} \textbf{102}, 083601 (2009).} imposing limitations on experimental complexity and necessitating an indirect measure of strong coupling.$^{2}$ Using fast logic electronics, we achieve real-time detection of falling atom transit events of duration 2-4 $\mu$s in 250 ns followed by conditional switching of the input beam while the atom is coupled to the cavity. Laser detuning and intensity switching after atom detection enables measurement of Rabi splitting, directly confirming strong coupling. Monte Carlo simulations of atom trajectories and spectra reveal that transits detected in real-time serve as a probe of dipole and van der Waals forces between resonator and atom, here in a regime of strong atom-cavity coupling. [Preview Abstract] |
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T1.00014: Magnetic field detection and imaging with atomic Rb vapor Eugeniy Mikhailov, Kevin Cox, Irina Novikova, Frank Narducci, Mark Havey We demonstrate dynamic imaging of magnetic fields using electromagnetically induced transparency in hot Rb vapor. The prototype device is demonstrated and discussed. We also investigate the possibility to extend the method to find the direction of magnetic field. As an experimental demonstration we employ an atomic Rb gas confined in a glass cell to image the transverse magnetic field created by a long straight wire. [Preview Abstract] |
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T1.00015: Noise characteristics of millihertz lasers with group II atoms Dominic Meiser, Murray J. Holland Group II atoms have the potential to allow us to build lasers with ultra narrow linewidths in the millihertz range. For applications of the light source in precision metrology and timekeeping it is essential to understand the noise properties of this device. Here we present results on the intensity correlations as well as the phase stability this light source. We show that in the regime of collective emission the light is basically in a coherent state with a linewidth that is determined by the single atom decay rate. [Preview Abstract] |
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T1.00016: Electromagnetically Induced Transparency in a $\Lambda$-type Molecular System Angelos Lazoudis, Li Li, Teodora Kirova, Jianbing Qi, Ergin Ahmed, Marjatta Lyyra We present an experimental study of EIT in a $\mathbf{\Lambda}$ -type molecular Lithium System. Co-propagating beam geometry is utilized in order to minimize the residual Doppler width. Single channel fluorescence was detected by using phase sensitive detection in our experiments. A coupling laser power dependent study of the EIT feature was carried out. Our findings have been complemented by theoretical studies of open systems that trace the presence of EIT starting from the density matrix equations. Numerical simulations have been performed and are in excellent agreement with the experimental results. [Preview Abstract] |
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T1.00017: Polarization Rotation and Circular Dichroism Near the Potassium D2 Lines Charles Conover, Htet Thiha, Jennifer Dahnke We have experimentally measured the Faraday rotation and the differential absorption of the two circular polarizations for light tuned near the D2 line in potassium (766.7 nm). In particular we have explored the vapor temperature and magnetic field dependence of the frequency of the zero crossings of the lineshapes from the circular analyzer and the balanced polarimeter used in the measurements. These signals are routinely used as frequency references for laser locking and we discuss the sensitivity to experimental parameters. [Preview Abstract] |
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T1.00018: Modified Fresnel Laws for Optical Microcavities D. Gagnon, G. Painchaud-April, J. Poirier, L.J. Dub\'e The scattering of waves at a planar interface between two dielectric media is governed by Fresnel laws. The associated Fresnel coefficients exhibit a discontinuity at the critical angle of incidence, $\chi_c$, resulting in total internal reflection for $\chi \geq \chi_c$. However modern microresonators are often so small that corrections to the planar approximation become necessary. For instance, a plane wave incident on a curved interface can escape the optically denser medium even for angles larger than $\chi_c$. In the spirit of Snyder and Love [1], we have derived {\em smooth} reflection and transmission coefficients. Interface curvature is accounted for by only modifying the wavefunction describing propagation in the less optically dense medium. The theory is applied to dielectric cavities and our results compared to those of an independent calculation obtained from a sequential-reflection model [2]. The advantages and limitations of our alternative approach will be discussed at the conference.\\[4pt] [1] A. W. Snyder and J. D. Love, \textit{IEEE Trans. Microwave Theory Tech.}, \textbf{23}, 134--141, 1975.\\[0pt] [2] M. Hentschel and H. Schomerus, \textit{Phys. Rev. E.}, \textbf{65}, 045603(R), 2002. [Preview Abstract] |
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T1.00019: Phase Space Engineering in Optical Microcavities I. Preserving near-field uniformity while inducing far-field directionality G. Painchaud-April, J. Poirier, D. Gagnon, L.J. Dub\'e Optical microcavities have received much attention over the last decade from different research fields ranging from fundamental issues of cavity QED to specific applications such as microlasers and bio-sensors. A major issue in the latter applications is the difficulty to obtain directional emission of light in the far-field while keeping high energy densities inside the cavity (i.e. high quality factor). To improve our understanding of these systems, we have studied the {\em annular cavity} (a dielectric disk with a circular hole), where the distance cavity-hole centers $d$ is used as a parameter to alter the properties of cavity resonances. We will present results showing how one can affect the directionality of the far-field while preserving the uniformity (hence the quality factor) of the near-field simply by increasing the value of $d$. Interestingly, the transition between a uniform near- and far-field to a uniform near- and directional far-field is rather abrupt. We can explain this behaviour quite nicely with a simple model, supported by full numerical calculations, and we predict that the effect will also be found in a large class of eigenmodes of the cavity. [Preview Abstract] |
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T1.00020: Phase Space Engineering in Optical Microcavities II. Controlling the far field J. Poirier, G. Painchaud-April, D. Gagnon, L.J. Dub\'e Optical microcavities support Whispering Gallery Modes (WGMs) with a very high quality factor $Q$. However, WGMs typically display a far-field isotropic emission profile and modifying this far-field profile without spoiling the associated high $Q$ remains a challenge. Using a 2D annular cavity, we present a procedure capable to achieve these two apparently conflicting goals. With the correspondence between the classical and the wave picture, properties of the classical phase space shed some light on the characteristics of the wave dynamics. Specifically, the \textit{annular cavity} has a well separated \textit{mixed} phase space, a characteristic that proves to be of crucial importance in the emission properties of WGMs. While the onset of directionality in the far-field may be achieved through parametric deformation, the distance cavity-hole centers, $d$ (see Painchaud-April \textit{et al.} at this Conference), this contribution presents a method to control the emission profile via a second parameter, the hole radius $r_0$. The influence of the classical dynamics to \textit{control and predict} the field emission will be demonstrated. [Preview Abstract] |
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T1.00021: Cold atoms inside a hollow core fiber for few-photon nonlinear optics Thibault Peyronel, Sebastian Hofferberth, Michal Bajcsy, Sofia Magkiriadou, Qiyu Liang, Michael Gullans, Alexander Zibrov, Vladan Vuletic, Mikhail Lukin Typically, interactions of light beams in nonlinear media are very weak at low light levels. Strong interactions between few-photon pulses require a combination of large optical nonlinearity, long interaction time, low photon loss, and tight confinement of the light beams. Here, we present an approach to overcome these issues that makes use of an optically dense medium containing a few hundred cold atoms trapped inside the hollow core of a photonic crystal fiber. In this poster we describe the experimental improvements to load, probe and manipulate cold atoms inside the hollow core of the fiber. We also discuss recent experiments regarding nonlinear optical interactions at extremely low-light levels. Especially, the use of EIT and slow-light opens the way to few-photon efficient all-optical switching. [Preview Abstract] |
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T1.00022: Recoil-induced Resonances as All-optical Switches F.A. Narducci, S.A. DeSavage, K.H. Gordon, D.L. Duncan, G.R. Welch, J.P. Davis We have measured recoil-induced resonances (RIR) [1,2] in our system of laser-cooled 85Rb atoms. Although this technique has been demonstrated to be useful for the purpose of extracting the cloud temperature [3], our aim was to demonstrate an all optical switch based on recoil-induced resonances. In addition to a very narrow ``free-space'' recoil-induced resonance of approximately 15 kHz, we also discovered a much broader resonance ($\sim 30$ MHz), caused by standing waves established by our trapping fields. We compare and contrast the switching dynamics of these two resonances and demonstrate optical switching using both resonances. Finally, we consider the applicability of the narrow, free-space resonance to the slowing of a weak probe field. [1] J. Guo, P.R. Berman, B. Dubetsky and G. Grynberg {\em PRA}, {\bf 46}, 1426 (1992). [2] (a) P. Verkerk, B. Loumis, C. Salomon, C. Cohen-Tannoudji, J. Courtois {\em PRL}, {\bf 68}, 3861 (1992). (b) G. Grynberg, J-Y Courtois, B. Lounis, P. Verkerk {\em PRL}, {\bf 72}, 3017 (1994). [3] (a) T. Brzozowski, M. Brzozowska, J. Zachorowski, M. Zawada, W. Gawlik {\em PRA}, {\bf 71}, 013401 (2005). (b) M. Brzozowska, T. Brzozowski J. Zachorowski, W. Gawlik {\em PRA}, {\bf 72}, 061401(R), (2005). [Preview Abstract] |
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T1.00023: Production of sub-shot noise light via spin-damping in an RF atomic magnetometer Orang Alem, Mike V. Romalis, Karen L. Sauer Spin-damping is a technique to feedback part of the optical signal from an atomic magnetometer to orthogonal electromagnetic coils in order to damp out any unwanted signal. Using this technique, the optically pumped magnetometer can quickly be prepared to detect the RF signal of interest, for instance the femtoTesla signal emitted from an explosive during nuclear quadrupole resonance detection. In our K magnetometer, a linearly polarized probe beam measures, through Faraday rotation, the transverse K magnetization induced by the RF signal. In our study of spin-damping, we found a surprising result -- the spin-damping suppresses not only the transients in the K atoms, but also the photon shot noise. Depending on the gain and phase in the negative feedback loop, we measure noise suppression levels up to an order of magnitude below photon shot noise. This sub-shot noise level demonstrates the correlation between the photons in the light and the K atoms in the atomic cell. While the current demonstration is in a closed loop, we will discuss the possibilities of creating an open-loop generation of a sub-shot noise beam. [Preview Abstract] |
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T1.00024: Dynamics of Photon in Positive Energy Space Woon Yeo A concept of positive energy space is introduced in this presentation. Dynamics of a photon in a positive energy space is explained here with an example of a photon propagating through multiple mediums of different density. When a photon goes through from air to glass the speed of photon decreases and when it exits from glass it resumes the original speed. This process of propagation is explained with the concept of positive energy space. In a double slit experiment, stream of photons passing through the slits create interference patterns. A double slit experiment with single electron at a time also creates interference patterns even though there are no second electrons to Interfere. A double slit experiment is modeled here with the dynamics of the positive energy space. The model contains two components. One is the interference by phase relationship and the second is the interference by positive energy space distribution. The single electron interference is, in the model, from the second component, positive energy space distribution. The streaming photons create patterns from both the phase relations and the positive energy space distribution. An experiment result with laser is presented that demonstrates the two components of double slit experiment. Demonstrated also is the interference pattern being created by adjacent beams traveling with different wave phase. The calculations for the positive energy space distribution of the double slits are also presented. [Preview Abstract] |
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T1.00025: Optical Precursor in Hot Rubidium Vapor Wenlong Yang, Matthew Springer, Alexandre Kolomenski, George Kattawar, Alexei Sokolov A pico-second pulse with center wavelength about 795nm was sent through a hot rubidium (Rb) cell. The output pulse was detected by a streak camera with 2 pico-second resolution. The experiment data showed the original pulse separates to a main pulse and a precursor which travels faster than the main pulse. This gives some experiment evidence of the formation of precursor when a step-function-shape electromagnetic pulse travels through a Lorentz absorber, which was proposed by Dr. A. Sommerfeld and Dr. L. Brillouin about 100 years ago. [Preview Abstract] |
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T1.00026: ``Piecewise'' vs. ``Coherently controlled'' adiabatic passage Evgeny Shapiro We develop a technique for executing robust and selective transfer of populations between pre-selected superpositions of energy eigenstates. Viewed in the frequency domain, our methods stem from the idea of Coherently Controlled Adiabatic Passage [1], in which several adiabatic passage pathways coherently add up to provide the desired population transfer. Viewed in the time domain, the methods work by piecewise accumulation of the wavefunction in the target wave packet, applying the Piecewise Adiabatic Passage technique [2] in the multi-state regime. The presentation will discuss the basic concepts behind the technique as well as recent theoretical and experimental developments [3,4]. \\[4pt] [1] P. Kral, I. Thanopulos, M. Shapiro, Rev. Mod. Phys. 79, 53 (2007). \\[0pt] [2] E.A. Shapiro et.al., Phys. Rev. Lett. 99, 033002 (2007). \\[0pt] [3] E.A. Shapiro, V. Milner, M. Shapiro, Phys. Rev. A 79, 023422 (2009). \\[0pt] [4] S. Zhdanovich et.al., Phys. Rev. A 80, 063405 (2009). [Preview Abstract] |
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T1.00027: Picosecond STIRAP on sodium vapor in a noble gas buffer Jim L. Hicks, Chakree Tanjaroon, Susan D. Allen, Joey Burdin, Steven Hoke, J. Bruce Johnson Stimulated Raman adiabatic passage (STIRAP) and stimulated emission pumping (SEP) measurements were made on sodium vapor as a function of buffer gas pressure for several noble gases. The transitions used for the pump and Stokes pulses were 3p ($^{2}$P$_{1/2}) \quad \leftarrow $ 3s ($^{2}$S$_{1/2})$ and 5s ($^{2}$S$_{1/2}) \quad \leftarrow $ 3p ($^{2}$P$_{1/2})$ respectively. The laser pulses were approximately 12 ps long and were near-Fourier-transform-limited. When pump and Stokes pulse energies were well above the minimum required for efficient STIRAP transfer, an increase in buffer gas pressure first increases and then decreases the STIRAP and SEP efficiencies. The dependence of the peak efficiency position is presented as a function of the sodium temperature, laser pulse energy, and the buffer gas that was used. The maximum in the STIRAP efficiency occurred at pump and Stokes wavelengths that were shifted relative to the optimum wavelengths in the SEP regime. [Preview Abstract] |
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T1.00028: Resonant dispersive waves generated with multi-input femtosecond pulses Kai Wang, Jiahui Peng, Alexei Sokolov We investigated the resonant dispersive waves generated by high- order dispersion theoretically. We considered two femtosecond pulses propagating in the kagome-lattice hollow-core photonics crystal fibers with different wavelength and time delay. With a phase difference, besides the two resonant dispersive waves produced by the third and fourth order dispersion, the other resonant dispersive wave in the visible range is generated in numerical calculation. Using two input femtosecond pulse might be applied to produce the ultrashort pulse. [Preview Abstract] |
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T1.00029: Non-adiabatic effects induced by the coupling between Raman modes Vishesha Patel, Svetlana Malinovskaya We study the effects of coupling between the vibrational modes on population dynamics upon application of femtosecond chirped laser pulses. In our model, the ground states of the two coupled TLSs are nondegenerate and the relative phase between them is zero. Chirp of the pump and Stokes pulse is same in the magnitude and opposite in the sign for the whole pulse duration. Under these conditions, the exact solution obtained in the Schr$\ddot{o}$dinger representation gives a mixed population distribution in the TLSs at the end of pulse resulted from non-adiabatic dynamics. However, the population for the uncoupled TLSs shows population inversion under the same conditions. Dressed state analysis is performed to help in understanding and interpretation of the results. [Preview Abstract] |
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T1.00030: NV diamond magnetometers for bioimaging T. Yeung, D. Glenn, D. Le Sage, L. Pham, P. Stanwix, L. Yi, Y. Zhao, P. Cappellaro, P. Hemmer, M. Lukin, A. Yacoby, R. Walsworth We are applying NV-diamond magnetometry to new tools for bioimaging, including a wide-field-of-view magnetic field imager for mapping neuronal network dynamics; functionalized diamond nanocrystals for imaging function in living cells; and super- resolution optical imaging techniques. Recent progress will be reported. [Preview Abstract] |
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T1.00031: Precision Magnetometry Using Ensembles of NV Spins in Diamond D. Le Sage, L. Pham, D. Glenn, P. Stanwix, T. Yeung, L. Yi, Y. Zhao, P. Cappellaro, P. Hemmer, M. Lukin, A. Yacoby, R. Walsworth We are developing precision magnetometers using ensembles of nitrogen-vacancy (NV) centers in room-temperature diamond. Magnetometry with single NV centers has demonstrated sensitivity on the order of 10 nT per root Hz. By simultaneously detecting the fluorescence signal from an ensemble of many NV centers, we achieve much higher magnetic field sensitivity. Further improvements will be possible with improved photon collection efficiency and reduced NV spin decoherence. Recent progress will be reported. [Preview Abstract] |
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T1.00032: A convenient high power high efficiency blue cw single frequency laser by IR diode laser doubling with PPKTP Koustubh Danekar, Ali Khademian, Nima Hassan Rezaeian, David Shiner We report on high efficiency resonant doubling to 486nm using periodically poled KTP. A stable blue power of 680 $\pm $ 5 mW was obtained using the 840 mW output power of a FBG stabilized PM fiber coupled IR semiconductor laser. This gives an overall conversion efficiency of 80{\%} for generating blue. To obtain this result, all losses in the system were carefully studied and minimized. Using a similar cavity design replacing PPKTP with CLBO we are additionally investigating a second doubling stage for efficient UV generation to 243nm. [Preview Abstract] |
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T1.00033: ATOMIC PHOTOIONIZATION AND PHOTODETACHMENT PROCESSES |
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T1.00034: Potential Barrier Features in Two-Photon Ionization Processes in Atoms Liang-Wen Pi, Anthony F. Starace The development of novel, intense, and tunable X-ray sources, such as the various FELs and SLAC's LCLS, opens a new regime in which nonlinear processes in the soft X-ray region can be investigated. As was the case in single-photon ionization processes, in which many prominent features in photoionization cross sections and in photoelectron angular distributions were understood by means of a model potential approach (see, e.g., A.F. Starace, Theory of Atomic Photoionization, \emph{Handbuch der Physik} {\bf 31}, ed. W. Mehlhorn (Springer-Verlag, Berlin, 1982), pp. 1-121), such an approach may be expected to provide similar understanding for multiphoton processes. We report here model potential results on the frequency dependence of two-photon ionization cross sections from inner subshells of rare gas and other closed-shell atoms. Our initial investigations focus on potential barrier effects. We use second order perturbation theory in the X-ray field and sum intermediate states using the well-known Dalgarno-Lewis method (A. Dalgarno and J.T. Lewis, Proc. R. Soc. A {\bf 233}, 70 (1955)). [Preview Abstract] |
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T1.00035: Turnstile approach to ionization of the hydrogen atom in crossed fields Korana Burke, Kevin A. Mitchell The motion of the electron of a hydrogen atom placed in crossed external electric and magnetic fields exhibits chaotic behavior. We explore the chaotic ionization in this system by appropriately choosing the surface of section and studying the geometry of a phase space turnstile (a geometric structure that regulates the ionization process). This approach has been used in the past to analyze numerous ionization and escape phenomena, e. g. hydrogen atom in parallel fields, kicked hydrogen atom and molecular dissociation. The choice of the surface of section in crossed fields is much more challenging than in the parallel fields case due to the reduced symmetry. We show the procedure for choosing the surface of section, computing the turnstile and we give insights into the ionization process. [Preview Abstract] |
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T1.00036: Overlapping Resonances in Atomic Ions W.-C. Chu, H.-L. Zhou, S.T. Manson The resonances in the low-energy region resulting from photoionization have been studied for the four-electron Be isoelectronic series. The Breit-Pauli R-matrix methodology has been employed [1]. In particular, the overlap of resonances converging to different thresholds have been analyzed and general rules formulated as to how this overlap changes with Z, along with the asymptotic high-Z behavior. For Be and B$^{+}$, the 4s4p resonance manifests as an isolated resonance. Starting with C$^{2+}$, however, this resonance overlaps with resonance series converging to the n=3 thresholds, i.e., the 4s4p resonance lies below the n=3 thresholds, and, since it is so much wider than the 3\textit{lnl' }resonances, it appears as a modulation on the intensities of the lower narrow resonances. With increasing Z, the 4s4p resonance moves to overlap with lower and lower members of the various 3\textit{lnl'} series and, by Ne$^{6+}$, it becomes completely mixed with the 3\textit{lnl'} resonances so that no modulation appears and its presence can be discerned only by examining the 3\textit{lnl'} in detail and noting the departures from regularity in the quantum defects and widths. It is expected that this sort of behavior is quite general for resonances along isoelectronic series over the entire periodic table. This work is supported by NSF and DOE. [1] W.-C Chu et al, J. Phys. B \textbf{42, }205003 (2009) and references therein. [Preview Abstract] |
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T1.00037: Experimental absolute cross section for photoionization of Xe$^{7+}$ S. Schippers, A. M{\"u}ller, D. Esteves, M. Habibi, A. Aguilar, A.L.D. Kilcoyne Collision processes with highly charged xenon ions are of interest for UV-radiation generation in plasma discharges, for fusion research and for space craft propulsion. Here we report results for the photoionization of Xe$^{7+}$ ions\footnote{S. Schippers et al., J. Phys.: Conf. Ser. (in print)} which were measured at the photon-ion end station of ALS beamline 10.0.1. As compared with the only previous experimental study\footnote{J. M. Bizau et al., Phys. Rev. Lett. 84, 435 (2000)} of this reaction, the present cross sections were obtained at higher energy resolution (50--80~meV vs.\ 200--500 meV) and on an absolute cross section scale. In the experimental photon energy range of 95--145~eV the cross section is dominated by resonances associated with $4d\to 5f$ excitation and subsequent autoionization. The most prominent feature in the measured spectrum is the $4d^9\,5s\,5f\,{^2\!P}$ resonance at $121.14\pm0.02$~eV which reaches a peak cross section of 1.2 Gb at 50~meV photon energy spread. The experimental resonance strength of 160~Mb~eV (corresponding to an absorption oscillator strength of 1.46) is in fair agreement with the theoretical result$^2$. [Preview Abstract] |
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T1.00038: Redistribution of Ce 4d Oscillator Strength Observed in Photoionization of Endohedral Ce@C$^+_{82}$ Ions A. M{\"u}ller, S. Schippers, M. Habibi, D. Esteves, R.A. Phaneuf, A.L.D. Kilcoyne, A. Aguilar, L. Dunsch The concept of an atom trapped inside a fullerene molecule has fascinated both chemists and physicists for the past two decades. Numerous theoretical studies have explored the response of atoms encapsulated in fullerene cages to ionizing electromagnetic radiation. We report on single and double photoionization experiments\footnote{A. M{\"u}ller et al., PRL 101, 133001 (2008).} with free atomic Ce$^{q+}$ ($q$=2,3,4), empty C$^+_{82}$ and endohedral Ce@C$^+_{82}$. From the measured cross sections the contributions of cerium $4d$ photoexcitation to the single and double ionization channels of the endohedral molecule have been extracted as well as information about the charge state ($q$=3) of the cerium atom residing within the fullerene shell. Comparing $4d$ photoionization of free and encasulated Ce$^{3+}$ we find a considerable reduction of the oscillator strength for the encaged ion. We speculate that this may be due to the redistribution of oscillator strength into additional (yet unmeasured) decay channels of the endohedral fullerene ion which are not availabale for the free atomic ion.\vspace*{-3pt} [Preview Abstract] |
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T1.00039: Satellite lines in the photoionization of ions; The Be isoelectronic sequence W.-C. Chu, H.-L. Zhou, S.T. Manson Partial photoionization cross sections for the $^{1}$S ground state and the $^{3}$P metastable state to various final states of Be-like ions have been calculated using the $R$-matrix method [1]. The relative strengths and the energy dependence of the partial cross sections are analyzed and their general behavior as a function of Z and energy are delineated. The partial cross sections display complex patterns as a function of energy, owing to interchannel coupling between strong and weak channels, and these patterns change smoothly as a function of Z. The ratios of the partial cross sections to the main line are found nearly constant of the photon energy if both are of the same angular momentum, and, at the higher energies, these ratios are explained well by the so-called shake-off model. \\[4pt] [1] W.-C. Chu et al, J. Phys. B \textbf{42}, 205003 (2009). [Preview Abstract] |
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T1.00040: Dynamics of electron wave propagation in photoionization microscopy: Semiclassical open-orbit theory Libo Zhao, John Delos Semiclassical open-orbit theory is used to describe the propagation of outgoing electron waves which are generated in photoionization of atoms in uniform strong electric fields. The spatial distributions of electron probability densities and current densities are predicted. The open-orbit theory, based on an assumption that electron waves propagate along classical paths from a point-like source to a detector, provides a clear and intuitive physical picture to interpret structures of observed geometrical interference patterns in photoionization microscopy. We calculated photoelectron ejection of hydrogen atoms in electric fields, and comparison is made with quantum-mechanical results. A strong quantum tunneling effect has been found. Such a tunneling effect should be visible in experiments. [Preview Abstract] |
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T1.00041: Photoionization of Ce$^{3+}$@C$_{82 }$ Zhifan Chen, Alfred Z. Msezane Photoionization cross section for the Ce$^{3+ }$@C$_{82}$ endohedral fullerene in the energy region 100-150 eV has been studied using our open-shell random phase approximation with exchange method and the C$_{82}$ model potential. Electron affinity (EA) of the C$_{82}$ has been calculated using the density functional theory. The C$_{82}$ fullerene was described by an attractive short range spherical well with potential V(r), given by V(r) =- V$_{0}$ for r$_{i}<$ r$<$ r$_{0}$, otherwise V(r) =0, V$_{0}$ was obtained by solving the resultant transcendental equation using the calculated EA value. The wave functions of the Ce$^{3+}$ confined inside the C$_{82}$ have been calculated by solving the Schr\"{o}dinger equation with both regular and irregular solutions and the continuous boundary conditions of the wave functions and their logarithmic derivatives at r$_{i}$ and r$_{0. }$Our calculation included 32 ionization channels from 5s, 5p and 4f subshells and 14 channels from the 4d$^{10}$ 4f +h$\nu \to $ 4d$^{9}$4f$^{2}$ photoexcitation.$_{ }$Finally the RPAE equation was solved to obtain the partial cross sections with a total of 16 $^{2}$D states, 16 $^{2}$G states and 14 $^{2}$F states. The photoionization of Ce$^{3+}$@C$_{82}$ shows both the resonance and suppression effect and demonstrates a more stronger resonance peak at 106 eV. [Preview Abstract] |
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T1.00042: Photoelectron angular distributions along Ar and Ca isonuclear sequences Gagan B. Pradhan, Jobin Jose, Vojislav Radojevic', Pranawa C. Deshmukh, Steven T. Manson The dipole angular distribution asymmetry parameter, $\beta $, for photoelectrons resulting from 2p photoionization of members of the Ar and Ca isonuclear sequences (Ar, Ar$^{6+}$, Ar$^{8+}$, Ca, Ca$^{2+}$, Ca$^{8+})$ has been studied using the relativistic random phase approximation (RRPA) [1] over a broad range of photon energy. In the absence of relaxation, it known that inner shell cross sections are essentially unchanged, as a function of photon energy, on the removal of outer shell electrons [2]. The situation is found to be different for angular distributions; the $\beta $ parameter is not constant, as a function of photon energy, when outer electrons are removed. However, with increasing photon energy, the $\beta $'s arising from the varying stages of ionization become essentially constant. The reason for this behavior is traced to the dependence of $\beta $ upon the Coulomb phase shifts which are not constant as a function of photon energy. At the higher energies, the Coulomb phase becomes less important, resulting in the $\beta $'s coalescing. [1] W. R. Johnson and C. D. Lin, Phys. Rev. A \textbf{20}, 964(1979). [2] G. Nasreen, S. T. Manson and P. C. Deshmukh, Phys. Rev. A \textbf{40}, 6091(1989). [Preview Abstract] |
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T1.00043: Tunable Infrared Photodetachment Spectroscopy of Ce$^{-}$ C.W. Walter, N.D. Gibson, R.L. Field III, D. Hanstorp The negative ion of cerium has been investigated using tunable infrared photodetachment spectroscopy. The relative cross section for neutral atom production was measured with a crossed laser-ion beam apparatus over selected photon energy ranges between 0.5 -- 0.6 eV. The spectrum reveals at least six sharp peaks due to negative ion resonances. The energies and widths of the resonances were determined by fitting with Fano profiles. The results suggest that at least some of these resonances are due to transitions from the Ce$^{-}$ (4$f$5$d^{2}$6$s^{2} \quad ^{4}H_{9/2})$ excited fine-structure level, which was recently predicted to be bound by 0.562 eV [1].\\[4pt] [1] S.M. O'Malley and D.R. Beck, Phys. Rev. A \textbf{79}, 012511 (2009). [Preview Abstract] |
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T1.00044: Correlation and relaxation effects near threshold in photoabsorption of the Ar isoelectronic series Jobin Jose, Gagan B. Pradhan, Vojislav Radojevic', Pranawa C. Deshmukh, Steven T. Manson The photoabsorption cross sections of the the 3s subshell of isoelectronic Cl$^{-}$, Ar and K$^{+ }$ have been calculated at various levels of approximation to understand how correlation and relaxation effects behave with increasing nuclear charge using the Relativistic Random Phase Approximation (RRPA) [1] and its modification, the RRPA-with- Relaxation (RRPA-R) [2]. To study the correlation in the form of interchannel coupling, RRPA was employed with and without coupling between the 3d and 3p photoabsorption channels. Interchannel coupling is found to dominate the 3s cross section for Cl$^{-}$, and become less and less important with increasing Z as discovered earlier for the Ne sequence [3]. Core-relaxation effects, of great importance for Cl$^{-}$, diminish with increasing Z. Thus, both interchannel coupling and core-relaxation must be included for even qualitative accuracy for negative ions, but these effects diminish with increasing Z. [1]. W. R. Johnson, C. D. Lin, Phys. Rev. A 20 964 (1979). [2]. V. Radojevic', M. Kutzner and H. P. Kelly, Phys. Rev. A 40, 727 (1989). [3]. H. S. Chakraborthy, P. C. Deshmukh and S. T. Manson, Ap. J. 595, 1312 (2003) [Preview Abstract] |
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T1.00045: Photoionization of ground and excited states of Ca$^{+}$ and comparison along the isoelectronic sequence A.M. Sossah, H.-L. Zhou, S.T. Manson Photoionization cross section calculations are performed on the ground ([Ne]3$s^{2}$3$p^{6}$4$s \quad ^{2}$S$_{1/2}^e )$ and the first two excited ([Ne]3$s^{2}$3$p^{6}$3$d \quad ^{2}$D$_{3/2}^e $ and [Ne]3$s^{2}$3$p^{6}$3$d$ $^{2}$D$_{5/2}^e )$ states of Ca$^{+}$ ions for photon energies from threshold to 45.0 eV using the relativistic (Breit-Pauli) R-matrix method. The discrete Ca$^{2+}_{ }$orbitals are generated using the computer program AUTOSTRUCTURE; 30 configurations are included in the configuration-interaction (CI) calculation for Ca$^{2+}$. The most prominent 3\textit{p $\to $ 3d }giant resonances are analyzed and identified, and our results are compared with experimental results, and rather good agreement is found. Using results of our previous photoionization calculations on Sc$^{2+}$ and Ti$^{3+}$ ions, the strongest and broadest resonances in the photoionization cross section of those three ions (Ca$^{+}$, Sc$^{2+}$ and Ti$^{3+})$, are compared in terms of width and oscillator strengths to show the evolution as a function of nuclear charge. This work is supported by DOE and NSF. [Preview Abstract] |
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T1.00046: Photoionization of potassium-like transition metal ions: Ti$^{3+}$ to Fe$^{7+}$ A.M. Sossah, H.-L. Zhou, S.T. Manson Photoionization cross section calculations are performed on potassium-like transition metal ions (Ti$^{3+}$, V$^{4+}$, Cr$^{5+}$, Mn$^{6+}$and Fe$^{7+})$ using both non-relativistic (LS-coupling) and relativistic (Breit-Pauli) $R$-matrix methods for the ground ([Ne]3$s^{2}$3$p^{6}$3$d$ $^{2}$D$_{3/2}^e )$ and the first excited ([Ne]3$s^{2}$3$p^{6}$3$d$ $^{2}$D$_{5/2}^e )$ states of each of the five ions. Photon energies up to the first 3p ionization threshold are considered. The results show that for Ti$^{3+}$, the cross sections are dominated by the giant (3\textit{p $\to $ }3$d)$ resonances which are analyzed and identified, while for the four other ions (V$^{4+}$, Cr$^{5+}$, Mn$^{6+}$and Fe$^{7+})$, the 3\textit{p $\to $ }3$d$ resonances lie below the ionization threshold, and the cross sections are dominated by 3$p^{5}$3$d$ \textit{ns} and 3$p^{5}$3$d$ \textit{nd} Rydberg series of resonances. Comparison of the Ti$^{3+}$ results with available theoretical and experimental data shows good agreement. This work is supported by DOE and NSF. [Preview Abstract] |
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T1.00047: Trapping and cooling of Sr+ ions: strings and large clouds Quentin Glorieux, Romain Dubessy, Samuel Guibal, Luca Guidoni, Jean Pierre Likforman, Thomas Coudreau, Sebastien Removille Large and cold ion clouds are very promising media for quantum information processing and quantum memories [1,2]. We report on the trapping and laser cooling of large clouds of singly ionized strontium ions in a linear Paul trap. We describe our loading technique based on two-photon absorption of femtosecond pulses and compare it to electron-bombardment ionization. The sample are Doppler-cooled to form Coulomb crystals both in the few-ion regime and in the case of large clouds. Our setup is designed, in particular, to obtain optically dense clouds in the perspective of an ion-based quantum memory for continuous variables [2]. We present absorption measurements, that are consistent with the estimated number of ions present in the trap. These experiments open the way to the use of a large cold trapped-ion cloud for the realization of a long-lived quantum memory. \begin{thebibliography}{99} \vspace{-.4cm} \bibitem{Drewsen} Herskind P et al., Appl. Phys. B 93 373 (2008) \vspace{-.2cm} \bibitem{our2009} Coudreau T et al., J. Phys. B: At. Mol. Opt. Phys. 40 413 (2007) \end{thebibliography} [Preview Abstract] |
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T1.00048: Photoionization of potassium from the ground and excited states Swaraj Tayal, Oleg Zatsarinny The available experimental cross sections for photoionization of neutral potassium from the ground state differ by up to a factor of 2. The theoretical calculations for photoionization of potassium at small energies also differ considerably with each other and from the experimental results. The current calculations do not reproduce accurately the minimum in measured cross sections where short-range correlation and relativistic effects are very important. We have calculated photoionization cross sections from the ground 4s and excited 4p, nd (n=3-5), and ns (n=5-7) states using fully-relativistic approach based on the Dirac-Coulomb Hamiltonian. We use the B-spline box based multi-channel method to generate the target states. The B-spline expansion coefficients have been obtained by diagnoalization of the atomic Dirac-Coulomb Hamiltonian. The photoionization of potassium is strongly effected by core-polarization effects. In our work we provide a detailed study of these effects by including the dipole, quadrupole, and octupole core-polarization to full extent. Our results for phtoionization from the ground and excited states are compared with available measurements and calculation. [Preview Abstract] |
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T1.00049: Inner-shell photodetachment from Se$^{-}$ N.D. Gibson, C.W. Walter, R.L. Field III, D.J. Carman, J.Z. Shapiro, R.C. Bilodeau, I. Dimitriu, N. Berrah, A. Aguilar, D. Hanstorp The photodetachment spectrum of Se$^{-}$ has been investigated using the merged ion-photon beam photodetachment technique. Se$^{-}$ ions were produced in a Cs sputtered negative ion source (SNICS II) while the photons were produced by the undulator on the Advanced Light Source Ion-Photon Beamline 10.0.1. Positive Se ions formed by multiple detachment were detected as a function of photon energy. Correlations in short-lived negative ion resonances formed by completely filling the valence 4$p$ shell in Se$^{-}$ by photoexcitation of 3$d $electrons lead to three resonance structures above 50 eV. The 3$p $threshold is observed above 156 eV and multielectron detachment resonance structure is observed near the 3$s$ photodetachment threshold above 220 eV. Comparisons to inner-shell detachment from S$^{-}$ and Te$^{-}$ are discussed. [Preview Abstract] |
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T1.00050: Systematics of nondipole effects on photoelectron angular distributions for 3s and 4s photoionization in the region of quadrupole Cooper minima L.A. LaJohn, R.H. Pratt, S.T. Manson Dipole effects are dominant in low energy photoeffect integrated cross sections, but quadrupole effects on differential cross sections (DCS) can be quite substantial, due to the presence of dipole-quadrupole interferences terms in the angular distribution parameters $\gamma $ and $\delta $. At low photon energies, quadrupole effects are seen in the parameter $\gamma $, dependent on dipole and quadrupole matrix elements and the cosines of phase shift differences. Calculations have been performed over a broad range of Z and a number of Cooper minima in $3s\rightarrow \epsilon d$ and $4s\rightarrow \epsilon d$ quadrupole transitions have been found for photon energies below 100 eV. The locus of these quadrupole matrix zeros (QMZ) have been mapped out; they appear above the ionization threshold for Z's of 11-30 for 3s and 19-50 for 4s. The nondipole photoelectron angular distribution parameter $\gamma $ has been calculated for these Z's, and significant variations, as a function of photon energy, have been found. In particular, $\gamma = 0$ at the location of the QMZ, and also is zero where the cosine of the p-d phase shift difference vanishes. On the other hand, $\gamma $ has a maximum in the vicinity of dipole Cooper minima. The combined effects of these three types of zeros create the pattern of variations of $\gamma $ as a function of energy and Z. [Preview Abstract] |
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T1.00051: Accurate calculations of H$^-$ photodetachment and radiative attachment for astrophysical applications P.C. Stancil, B.M. McLaughlin, H.R. Sadeghpour, A. Dalgarno, R.C. Forrey We combine new accurate calculations, asymptotic relations, and available experimental data to construct an H$^-$ photodetachment cross section reliable for a large range of photon energies. In particular, account is taken of the series of auto-detaching shape and Feshbach resonances between 10.92 and 14.35 eV. The accuracy of the cross section is controlled by ensuring that it satisfies all known oscillator strength sum rules including contributions from the resonances and double photodetachment. From the resulting recommended cross section, spontaneous and stimulated radiative attachment rate coefficients are obtained. Photodetachment rates are also computed for the standard interstellar radiation field and in diffuse and dense interstellar clouds assuming the total-to-selective-extinction ratio $R_V=3.1$. Implications of the new cross sections and rate coefficients are discussed for a variety a astrophysical environments. [Preview Abstract] |
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T1.00052: Study of the Ce@C$_{82 }$endohedral fullerene Zhifan Chen, Alfred Z. Msezane Ce@C$_{82}$ endohedral fullerene has been studied using the DFT, GW approximation and TDDFT. In the simulation of Ce@C$_{82}$, a Ce atom was added inside the C$_{82}$-C$_{2v}$ isomer along the C$_{2}$ axis. The Ce atom can be moved along that axis to find the minimum energy of the system. Three electrons have been removed from the Ce atom and a -0.5 electron has been added to each C atom of the six-membered ring of the C$_{2}$ axis to make the system neutral. A geometry optimization for a total of 550 electrons has been performed under the generalized gradients approximation (GGA) with the PW91 exchange-correlation functional. All electrons in the core were explicitly included in the calculation. Valence electrons were described by a double numerical basis set. The results of geometry optimization suggest that the Ce atom is situated off center by about 1.79{\AA} which is compatible with the X-ray diffraction pattern data of 2{\AA}. The density of the states, and density of the electrons for the Ce@C$_{82 }$fullerene have also been calculated in the DFT. The band gap of 0.06 eV was obtained by the GW approximation. The optical absorption spectra are evaluated using TDDFT, RPA, and BSE. [Preview Abstract] |
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T1.00053: Theoretical study of strong field nonsequential double ionization of atoms Yaqiu Liang, Zhangjin Chen, C.D. Lin We study the strong field nonsequential double ionization of atoms based on the recently developed quantitative rescattering theory and the traditional laser-free (e, 2e) theory. Both the correlated electron momentum spectra and the integrated longitudinal distribution of ions are evaluated. We found that Coulomb interaction between the two outgoing electrons plays a crucial rule in the correlated electron momentum spectra while the longitudinal momentum distribution of ions is insensitive to how the two outgoing electrons are treated. In addition, the CEP (carrier envelope phase) dependence of the ion momentum distribution is also investigated. [Preview Abstract] |
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T1.00054: Double Auger Decay following K-Shell Photoionization of Neon M.P. Jones, M. Schoffler, T. Jahnke, K. Kreidi, J. Titze, R. Dorner, C. Stuck, Th. Weber, A. Belkacem, A. Landers Using a COLTRIMS setup at LBNL-ASL, our group photoionized Neon just above the K-ionization threshold. The measurement allows us to investigate a simultaneous angular and energy correlation between the three continuum electrons of the subsequent double Auger decay pathway: \begin{center} Ne(1s$^{-1})^{+}$ + e$^{-}_{photo }\to $ Ne$^{3+}$ + e$^{-}_{photo}$ + e$^{-}_{Auger}$ + e$^{-}_{Auger}$, \end{center} where we measure two of the electrons directly and infer the momentum of the third through momentum conservation of the four-particle final state. Analysis is underway to better understand the k-hole relaxation process following photo-ionization and successive Auger decay(s). [Preview Abstract] |
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T1.00055: How to probe the time evolution of a Fano resonance? W.-C. Chu, C.D. Lin We study the autoionization process in the time domain of a Fano resonance. A pump beam is used to generate a bound state and the nearly background continuum. The time evolution of the resulting electron wave packet till the full decay of the bound state is investigated. Using the 2s2p($^{1}$P$^{o})$ resonance in neutral helium as an example, we study how the wave packet can be probed by ionizing the remaining bound 2s2p($^{1}$P$^{o})$ component or by ionizing the inner electron of the whole wave packet. We show that the lifetime of the resonance can be obtained from the total ionization yield vs the time delay but the q-parameter can be determined from the electron spectra. [Preview Abstract] |
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T1.00056: Theory of probing attosecond electron wave packets via two-path interference of angle-resolved photoelectrons N.N. Choi, T.F. Jiang, W.-C. Chu, C.D. Lin We study theoretically the electron wave packet generated by an attosecond pulse train (APT) which is probed with a time-delayed infrared (IR) laser pulse. The APT creates an excited state and a continuum electron wave packet. By ionizing the excited state with an IR, a delayed new continuum electron wave packet is created. The interference of the wave packets from the two paths, as reflected in the angle-resolved photoelectron spectra, is analyzed analytically. [Preview Abstract] |
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T1.00057: ULTRAFAST/STRONG FIELD |
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T1.00058: Production of Atomic Hydrogen and Deuterium from H$_{2}$, D$_{2}$ and HD Photodissociation J.R. Machacek, V.A. Andrianarijaona, J.E. Furst, T.J. Gay, A.L.D. Kilcoyne, A.L. Landers, E.T. Litaker, K.W. McLaughlin We have measured the production of Ly$\alpha $ and H$\alpha $ fluorescence from atomic H and D resulting from the photodissociation of H$_{2}$, D$_{2}$ and HD by linearly-polarized photons with energies between 22 and 64 eV. In this energy range, excited photofragments result primarily from the production of doubly-excited molecular species which promptly autoionize or dissociate into two neutrals. Comparison between the current relative cross section results, previous absolute and relative experimental results and the available theory show only qualitative agreement. We will discuss the various systematic effects which affect this and other types of synchrotron-based measurements in this energy range. Support provided by the NSF (Grant PHY-0653379), DOE (LBNL/ALS) and ANSTO (Access to Major Research Facilities Programme). [Preview Abstract] |
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T1.00059: Effect of Removing Occupied Orbitals Under the Single-Active-Electron Approximation J.V. Hern\'andez, B.D. Esry We present the results of using the single-active-electron approximation to treat multi-electron atoms in intense laser fields. In particular, we investigate the effect of not removing the occupied orbitals on the above threshold ionization spectrum, as well as the effect of how the occupied orbitals are removed. The occupied orbitals are eliminated from the system by various methods such as: a soft repulsive core [1], $\ell$-dependent pseudopotentials [2,3], and exactly in a basis set expansion. Special attention is paid to the high energy ($>$27 eV) portion of the spectrum where back-scattering occurs and the details of the atomic core are more strongly probed. \\[4pt] [1]H.G. Muller, Phys. Rev. A {\bf 60} 1341 (1999).\\[0pt] [2]M.B. Gaarde {\it et al.}, Phys. Rev. Lett. {\bf 84} 2822 (2000).\\[0pt] [3]W.J. Stevens {\it et al.}, Can. J. Chem. {\bf 70} 612 (1992). [Preview Abstract] |
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T1.00060: Langmuir chains of ions in linearly and circularly polarized electromagnetic field crossed with the magnetic field Matt Kalinski We have recently discovered that so called Langmuir [1] states of Helium can stabilize in both the circularly polarized electromagnetic and the magnetic fields when the fields are crossed and two electrons are rotating in the configuration when the two parallel single-electron circular trajectories have the both particles moving in the spatial phase. The stability islands in the fields strength planes have exotic shapes and the configurations are bistable geometrically. Here we discover the whole chains of ions when the single Langmuir configuration is additionally experiencing the infinite chain of neighbouring ions and alike space-periodic configurations. This leads to self-stabilization and Born-Opennheimer binding of Hydrogen, helium or higher charged ions in chains parallel to the magnetic field and when the CP field vector is perpendicular. The excitations along the chain are plasmon-like and have the physical meaning of the deviation from the CP field rotation helicity. Ones the linearly polarized field is superposed from two circularly polarized counterrotating fields similar configurations exist by the geometric argument. Numerical simulations using the recently discovered Cartesian-hypespherical coordinates method previously applied to Langmuir configurations themself are also presented. [1] M. Kalinski, L. Hansen, and D. Farrelly, ``Nondispersive Two-Electron Wave Packets in a Helium Atom,'' Phys. Rev. Lett. {\bf{95}}, 103001 (2005). [Preview Abstract] |
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T1.00061: Effects of screening of the final-state $A^{+}$ ion static potential within the C$_{60}$ on $A$@C$_{60}$ photoionization. Valeriy Dolmatov, Emre Guler, Steven Manson We perform a novel, trial study of photoionization of an atom $A$ in the $A$@C$_{60}$ endohedral fullerene within the framework of the model [1] which regards C$_{60}$ as a conducting sphere, approximated by an attractive square-well potential $V_{{\rm C}_{60}}(r)$ of a given inner radius, depth, and thickness. In the present study, we explore the possible shielding, both partial and complete, of the Coulomb potential of the final-state $A^{+}$ ion by the C$_{60}$ in the region between the inner and outer radii of $V_ {{\rm C}_{60}}(r)$. This effect has not been studied previously and its significance remained unknown. Using the example of Ne@C$_ {60}$, we find that, fortunately, the effect of the shielding on the photoionization of endohedral atoms is relatively small; no more than 20$\%$ near threshold for a complete screening, and much less at higher energies. Thus, the results and predictions of earlier studies are not significantly impacted by this shielding and future studies may ignore the shielding effect, to a good approximation. \\[4pt] [1] V. K. Dolmatov. In: \textit{Theory of Confined Quantum Systems: Part Two}, edited by J. R. Sabin and E. Br\"{a}ndas, Advances in Quantum Chemistry (Academic Press, New York, 2009), Vol.\ 58, pp. 13-68. [Preview Abstract] |
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T1.00062: ABSTRACT HAS BEEN MOVED TO L5.00010 |
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T1.00063: Characteristic Features In Low Energy Photoionization of O~II M. Montenegro, Sultana Nahar, W. Eissner, A. Pradhan The low-energy resonant features due to fine structure in photoionization of the ground state $2p^3~^4S^o_{3/2}$ of O~II are found for the first time. These resonances appear in the small energy difference between the fine structure levels of the ground state of the residual ion O~III ($2p^2~^3P^o_{0,1,2}$), and are expected to play an important role in low-temperature dielectronic recombination and the formation of O~II recombination lines. The recombination rates should be able to explain the current discrepancy of O~II abundance in astrophysical plasmas. The calculations have been carried out in the relativistic Breit-Pauli R-matrix (BPRM) method. The BPRM codes have been advanced further in accuracy recently by including the two-body magenetic terms of Breit interaction not existed before. We will present level-specific and partial state-resolved photoionization cross sections of O~II to illustrate the new features. We will also present individual and combined theoretical results for photoionization of several excied states that are found to be in agreement with two experimental measurements, thereby identifying the excited O~II levels present in the ion beams. [Preview Abstract] |
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T1.00064: Small Classical Phase Space Structures and Pulsed Quantum Evolution: the Stepwise Ionization of the Excited Hydrogen Atom in a Microwave Pulse Luca Perotti Microwave ionization probability of a highly excited almost monodimensional hydrogen atom subjected to a microwave pulse sometimes grows in steps when the peak electric field of the pulse is increased. Classical pulsed simulations display the same steps as the laboratory experiments. These classical steps have been traced to phase-space metamorphoses. Quantum numerical calculations again exhibit the same ionization steps. I have shown that the time-sequence of two level interactions, responsible for the observed steps in the quantum picture, is strictly related to the classical phase space structures generated by the above mentioned metamorphoses. [Preview Abstract] |
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T1.00065: MOLECULAR HIGH-ORDER HARMONIC GENERATION AND PHOTOIONIZATION |
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T1.00066: \emph{Ab initio} study of the ellipticity of molecular high harmonic generation driven by linearly polarized laser fields Sang-Kil Son, Dmitry A. Telnov, Shih-I Chu A recent experiment has demonstrated that high-order harmonic generation (HHG) from aligned linear molecules can be elliptically polarized even driven by linearly polarized laser fields [Phys.\ Rev.\ Lett.\ 102, 073902 (2009)]. We perform fully \textit{ab initio} calculations of HHG from the ground and excited electronic states of H$_2^+$ with arbitrary orientation and detailed analyses for the polarization and phases of harmonic emissions to reveal theoretical origins of the ellipticity of molecular HHG. Our results predict that even for the one-electron system all harmonic emissions are elliptically polarized unless molecular alignment is parallel or perpendicular to the polarization of the driving laser field. The ellipticity of harmonic emissions is closely related to the symmetry of the molecular orbital and affected by two-center interference effects in HHG. For H$_2^+$, the ellipticity becomes large for the ground state that is approximated by a symmetric combination of the atomic orbitals, whereas it becomes small for the first excited state approximated by an antisymmetric combination. This observation can be generalized for the ellipticity of HHG from linear molecules. [Preview Abstract] |
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T1.00067: Time-dependent density functional theory calculation of strong field ionization rates of H$_2$ Xi Chu We first report a detailed numerical comparison of strong field ionization rates of the H$_2$ molecule using two TDDFT methods, the molecular ADK (MOADK) method, and an {\it ab initio} complex scaling (CS) method. The two TDDFT methods are TDSIC and TDLB$_\alpha$, respectively, and they both contain the correct long-range limit of the exchange-correlation potential. The comparison covers different internuclear distances, molecular orientations, and laser intensities. The two TDDFT methods give consistent results. In the DC field limit, they agree with the MOADK and the CS results when the laser intensity is relatively small. At larger intensities the TDDFT results are lower and present a knee structure when plotted against the intensity. We think this difference is due to the ionization of the ion, which is not considered by the MOADK or the CS methods. We further explore the influence of the photon energy. The rates for 800 nm lasers are significantly larger than the values predicted by the slow varying field approximation at lower intensities. This difference diminishes with increasing laser intensity. With a lower intensity DC field, TDDFT methods predict an anisotropy similar to the MOADK prediction. However, we find that both the photon energy and the laser intensity play a role in the anisotropy, which the MOADK method does not describe. [Preview Abstract] |
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T1.00068: Coupled electronic and vibrational dynamics of a molecular ion in a strong laser field Nicholas Vence, Robert Harrison, Predrag Krstic We study a response of a hydrogen molecular ion to the strong 2-cycle 800-nm laser pulse, using highly accurate numerical solution of the time-dependent Schrodinger equation in 4 spatial dimension. We use a computational approach which employs an adaptive, discontinuous spectral element basis as well as multiresolution analysis and separated representations of operators for efficient computation in multiple dimensions (MADNESS). The basis (tensor product of Legendre polynomials) automatically adapts to meet the requested precision, while the time--dependent evolution of the system is considered using an efficient Chin-Chen propagator. We vary the laser polarization with respect to the fixed molecular axis, while the coupled electron and vibrational dynamics enables calculation of the ionization, dissociation and high-harmonic generation at the ``same footing''. [Preview Abstract] |
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T1.00069: PHOTON INTERACTIONS WITH ATOMS, IONS, AND MOLECULES |
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T1.00070: Role of Vibrational Excitations in High-Order Harmonic Generation A.L. Harris, Cheng Jin, Anh-Thu Le, C.D. Lin We carry out theoretical calculations to study the role of vibrational excitations in high-order harmonic generation of molecules by intense laser fields. The validity of the Franck-Condon Principle has been investigated in strong field ionization of molecules, as well as in the recombination step. We compare HHG yields of H$_{2}$ and D$_{2}$ using IR lasers with different wavelengths and peak intensities to uncover the dynamics of vibrational states, including their coherence, in the harmonic generation process. [Preview Abstract] |
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T1.00071: THE IRON PROJECT AND THE RMAX PROJECT: Photoionization, Electron-IonRecombination and Oscillator Strengths of Fe Ions, Fe~XVII and Fe~XIX Werner Eissner, Sultana Nahar, Anil Pradhan The aims of the Iron Project and the Rmax Project are detailed study of radiative and collisional processes of astrophysically abundant atoms and ions, mainly iron and iron-peak elements, over a wide energy range, from infra-red to X-rays. We will present the complete results on photoionization, partial and total, of fine structure levels with n $\leq$ 10 of Fe~XVII. They correspond to a large-scale computation using a wave function expansion containing 60 levels of the core. Preliminary results on total recombination rate coefficients ranging over low to very high temperatures, especially where the ion is abundant in astrophysical plasmas, will be presented. We will also report the latest results on oscillator strengths for photo-excitations in Fe~XIX. This highly charged nitrogen-like iron ion has over thousands of bound fine structure levels. The calculations have been carried out in relativistic Breit-Pauli R-matrix (BPRM) method. The forbidden electric quadrupole, electric octupole, magnetic dipole and magnetic quadrupole transitions for Fe~XIX correspond to fine structure levels upto 4p obtained from atomic structure calculations in Breit-Pauli approximation. [Preview Abstract] |
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T1.00072: Suppression of confinement oscillations in photoionization cross sections of endohedral A.S. Baltenkov, U. Becker, S.T. Manson, A.Z. Msezane Using a model representing the C$_{60}$ cage as a spherical shell formed by smeared carbon atoms, the shape effect of potential U(r) on the photoionization of atom A in A@C$_{60}$ is studied. For potential shell thickness, d less than 1.3-1.5 a.u., confinement oscillations in photoionization cross section of A in A@C$_{60}$ weakly depend on shape of U(r). With increasing d confinement resonances disappear. Additionally, we demonstrate that displacing A from the center of C$_{60}$ cavity also diminishes the amplitude of confinement resonances and results in their disappearance with increasing displacement. The nature of the suppression of confinement oscillation amplitudes is different in the two cases. In the first case, it is due to weakening of the connection of photoelectron wave function oscillations inside and outside the fullerene shell as the thickness of the spherical resonator wall increases. For the off-center position of the atom, it is due to mixing and mutual cancellation of confinement oscillations corresponding to different photoelectron trajectories inside the fullerene cavity. This could explain the absence of confinement effects in 4d photoionization measurement of the off-center Ce atom in Ce@C$_{82}^{+}$ [1]. \\[4pt] [1] A. M\"{u}ller et al, Phys. Rev. Lett. 101, 133001 (2008) [Preview Abstract] |
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T1.00073: Absolute Photoionization of Se and Xe Ions for the Determination of Elemental Abundances in Astrophysical Nebulae David Esteves, Nicholas Sterling, A.L.D. Kilcoyne, Rene Bilodeau, Eddie Red, Ghassan Alna'Washi, Ronald Phaneuf, Brendan McLaughlin, Connor Ballance, Alex Aguilar The determination of elemental abundances in astrophysical nebulae is highly dependent on the accuracy of atomic data. Absolute single photoionization cross sections for Se$^{+}$, Se$^{2+}$, Se$^{3+}$, Se$^{5+}$, Xe$^{+}$ and Xe$^{2+}$ have been measured at the ALS at Lawrence Berkeley National Laboratory using the merged-beams technique. All ions except Se$^{5+}$ were measured from the metastable region to at least 10 eV above the direct ionization threshold. Theoretical calculations for Se$^{5+}$ indicated strong resonances above 100 eV would dominate, therefore this region was explored for this ion. Rydberg series are identified for each ion and the experimental results are compared to theoretical photoionization cross section calculations using fully relativistic Dirac R-matrix code (DARC). This research was supported by both the DOE and NASA. [Preview Abstract] |
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T1.00074: Photoionization Cross-Section Measurements of the 5P$_{3/2}$ Excited State of Laser-Cooled Rubidium Alina Gearba, Brad Crochet, Kileigh Peturis, Charles Young Photoionization cross-section measurements are relevant for fundamental tests of the atomic theory, as well as state-selective detection of trapped atomic and molecular species and plasma research, including ultracold plasma formation. We have extended the current photoionization cross-section measurements of the 5P$_{3/2}$ exited state of rubidium by including three additional wavelengths close to the ionization threshold of 479.1 nm. The measurements were performed in a rubidium magneto-optical trap using several lines from a mixed argon-krypton ion laser ranging from 457.9 nm to 476.5 nm. The photoionization rate for each wavelength was determined from the loss rate of atoms in the trap during exposure to the ionizing laser radiation. Our results are in good agreement with other experimental results and allow for comparison with theoretical predictions of the photoionization cross section versus the ionizing photon energy. [Preview Abstract] |
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T1.00075: Modeling polarization reversal in optically pumped rubidium vapors J.M. Dreiling, E. Norrgard, T.J. Gay Rubidium atoms can be polarized by optical pumping with a resonant circularly polarized laser beam. Using Faraday rotation polarimetry [1], we have observed a flip in the sign of the Rb electron polarization when the wavelength of the pump laser is varied over the D1 absorption spectrum. This could occur if F $<$ (I + J) states with M$_{F}$ = F are predominantly populated at specific pump frequencies resulting in different spin polarizations. We have used a simple rate equation model to estimate the final electron polarization under the assumption that we are able to pump only one F transition at a time. The results of these calculations will be presented. \\[4pt] [1] H. Batelaan, A.S. Green, B.A. Hitt, and T.J. Gay, Phys. Rev. Lett. \textbf{82}, 4216 (1999). [Preview Abstract] |
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T1.00076: Three dimensional time dependent Schr\"odinger equation solver for multiple charge center systems Nicolas Bigaouette, Edward Ackad, Lora Ramunno We extended a method to solve the time dependent Schr\"odinger equation in 3D [1] to study multi charge centers in the single active electron approximation. It is based on a well-known computational electromagnetism algorithm called Finite-Difference Time-Domain. Our method can be used both to solve for the electronic wavefunctions in an arbitrary potential shape (independent of the presence of any symmetry), and to calculate the solution of time-dependent systems. As a first step, we verify our method by solving for the eigenstates of the H$_{2}^{+}$ molecule. Further, we investigate more complicated multicore systems, such as small charged atomic clusters. \\[4pt] [1] I W. Sudiarta et. al. J. Phys. A 40 (2007) 1885 [Preview Abstract] |
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T1.00077: K-Shell Photoabsorption Studies of the Carbon Isonuclear Sequence M.F. Hasoglu, Sh. A. Abdel-Naby, T.W. Gorczyca, B.M. McLaughlin, J.J. Drake Photoabsorption cross sections for the isonuclear C - C$^{3+}$ ions have been computed using an R-matrix method with the inclusion of important Auger broadening effects. Comparison with existing C$^+$, C$^{2+}$, and C$^{3+}$ experimental results for the lowest $1s\rightarrow 2p,3p$ resonances shows good agreement in general for the resonance strengths and widths, but the computed resonance positions differ from the observed positions by as much as 0.45~eV. Higher $np$ resonances and the above-threshold K-shell photoionization cross sections are also computed in order to produce an entire absorption profile as a function of X-ray photon energy. These computed cross sections are used to model the {\em Chandra} X-ray absorption spectrum of the blazar Mkn 421 near the carbon K-edge, thereby obtaining instrumental and interstellar carbon-ion abundances. [Preview Abstract] |
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T1.00078: Suppression of confinement oscillations in photoionization cross sections of endohedral atoms A.S. Baltenkov, U. Becker, S.T. Manson, A.Z. Msezane Using a model representing the C$_{60}$ cage as a spherical shell formed by smeared carbon atoms, the effect of the shape of potential U(r) on the photoionization of atom A localized inside the C$_{60}$ cage has been studied. It is shown that for potential shell thickness not exceeding 1.3-1.5 atomic units, confinement oscillations [1] in the photoionization cross section of endohedral atom A@C$_{60}$ weakly depend on the shape of U(r). With increasing width of the potential well the confinement resonances disappear. In addition, it is demonstrated that displacing the doped atom from the center of the C$_{60}$ cavity also diminishes the amplitude of confinement resonances and results in their disappearance with increasing displacement. The nature of the suppression of confinement oscillation amplitudes is different in the two cases. In the first case, it is due to weakening of the connection of photoelectron wave function oscillations inside and outside the fullerene shell as the thickness of the spherical resonator wall increases. For the off-center position of the atom, it is due to mixing and mutual cancellation of confinement oscillations corresponding to different photoelectron trajectories inside the fullerene cavity. This could be the reason confinement effects were not observed in the experiments on 4d photoionization of the Ce atom in Ce@C$_{82}^{+}$ [2], because this atom is off-center, adhering to the inner surface of the strongly non-spherical C$_{82}$ cage. [1] V. K. Dolmatov, A. S. Baltenkov, J.-P. Connerade and S. T. Manson, Radiat. Phys. Chem. 70, 417 (2004); [2] A. M\"{u}ller \textit{et al,} Phys. Rev. Lett. 101, 133001 (2008) [Preview Abstract] |
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T1.00079: Line-core and line-wing features in the temperature-dependent Mg(3s3p-3s$^2$)-He(1s$^2$) emission/absorption spectra Moncef Bouledroua, Lamia Reggami The present study deals with the collisional broadening of the monoatomic magnesium, evolving in a helium gas, in the wavelength and temperature ranges 260-310 nm and 100-3000 K, respectively. The spectral profiles, generated from our theoretical computations, are based on the most recent potential energy curves and transition dipole moments. The purpose of this treatment is twofold. First, using the Baranger impact approximation, the width and shift of the line core of the spectra are determined and their variation law with temperature is examined. The obtained results agree quite well with those already published. Then, the satellite structures in the blue and red wings are analyzed quantum mechanically. The calculations show especially that the free-free transitions are the most contributive in the MgHe photoabsorption spectra and a satellite structure is observable beyond the temperature 2000 K around the wavelength 274 nm. [Preview Abstract] |
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T1.00080: Photoelectric Effect Formula Must Include Vibrational and Rotational as Well as Linear Kinetic Energies of Ejected Electron Stewart Brekke All matter has no motion, is moving linearly, vibrating and/or rotating singly or in some combination. Curvilinear motion is linear motion influenced by an external force field. Einstein proposed that through collisions in the material all linear kinetic energy is lost and only the energy from the impacting photon affects the linear kinetic energy of the ejected electron. However, the electron is also rotating and vibrating in the material and these kinetic energies may also be lost through collisions with other electrons in the material. Therefore, the ejected electron may also have rotational and vibrational motion as well as linear motion resulting from the energy of the incident photon. The current values of the work functions may have to be reevaluated slightly therefore. The formula for the Photoelectric Effect mut be changed to include the possibility of the total energy of incident photon also creating vibrational and rotational motion as well as linear motion in the ejected electron. Therefore the formula must be $hf = (1/2mv^2 + 1/2I\omega^2 + 1/2kx^2)max + \phi$. [Preview Abstract] |
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T1.00081: Every Mass or Mass Group When Created Will have No Motion, Linear, Rotational or Vibratory Motion, Singly or in Some Combination, Which May Be Later Modified by External Forces--A Natural Law Stewart Brekke Every mass or mass group, from atoms and molecules to stars and galaxies,has no motion, is vibrating, rotating,or moving linearly, singularly or in some combination. When created, the excess energy of creation will generate a vibration, rotation and/or linear motion besides the mass or mass group. Curvilinear or orbital motion is linear motion in an external force field. External forces, such as photon, molecular or stellar collisions may over time modify the inital rotational, vibratory or linear motions of the mass of mass group. The energy equation for each mass or mass group is $E=mc^2 + 1/2mv^2 + 1/2I\omega^2 + 1/2kx_0^2 + W_G + W_E + W_M.$ [Preview Abstract] |
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T1.00082: Laboratory and Modeling Studies of Velocity-Changing Collisions, Spin-Changing Collisions, and Magnetic Fields on Sodium Guidestars Natalie Kostinski, Ivana Dimitrova, William Happer Lasers used to produce sodium guidestars can cause optical pumping of Na atoms, but only interact with atoms that possess resonant Doppler shift. The number density of atmospheric constituents (e.g., Na, N2, O, O2) is so low, that there is minimal collision broadening of the optical absorption lines and distinct velocity groups can be excited. A goal of our work is modeling and laboratory studies of the correlations between the atomic spin polarization and the atomic velocity along the pumping beam. We believe this will aid in understanding the various mechanisms (collision processes, geomagnetic field) that can influence guidestar signal strength. This work should lead to a better understanding of the relative importance of strong and weak velocity-changing collisions. [Preview Abstract] |
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T1.00083: ATOMS IN OPTICAL LATTICES |
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T1.00084: Two-component Bosons in State-Dependent Optical Lattices Daniel Pertot, Bryce Gadway, Ren\'{e} Reimann, Bartosz Bogucki, Dominik Schneble Ultracold bosonic mixtures in combination with state-dependent optical lattices offer the possibility to experimentally investigate idealized models of condensed matter physics. Among them are spin-boson models or the two-component Bose-Hubbard model, which reduces to the anisotropic (XXZ) Heisenberg model in the limit of weak hopping and unit occupancy. Here, we report on experiments with mixtures of $^{87}$Rb in two different hyperfine states in a state-dependent optical lattice potential. We demonstrate atomic four-wave mixing of two-component matter waves and present results on interspecies interaction effects in the two-component Bose-Hubbard model, along with a discussion of recent experimental progress. [Preview Abstract] |
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T1.00085: Analytic descriptions of two atoms in a trap and around a magnetic Feshbach resonance Constantinos Makrides, Ming Li, Bo Gao We present an analytic description of two atoms in a trap and around a magnetic Feshbach resonance. It is achieved by combining a multiscale quantum-defect theory for two atoms in a symmetric harmonic trap\footnote{Y. Chen and B. Gao, Phys. Rev. A \textbf{75}, 053601 (2007).}, with a new analytic description of ultracold atomic interactions around a magnetic Feshbach resonance. The theory is applicable to both broad and narrow resonances, or anything in between, and is applicable to Feshbach resonances of arbitrary $l$. It will be illustrated for sample alkali-metal resonances of experimental interest. [Preview Abstract] |
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T1.00086: Real-Time Configuration Control of Optical Lattices Using an Optical Interferometer Dian-Jiun Han, Bow-Wen Shiau, Tzu-Ping Ku We present an experimental scheme for fast phase difference control of optical beams based on a simple, however robust setup of Mach-Zehnder interferometer.\footnote{Bor-Wen Shiau \textit{et al}., to be published in JPSJ (2010).} We demonstrate to smoothly tune the relative phase by 140\r{ } in 275 ms, with an average peak-to-peak phase difference jitter less than 0.9\r{ }. The overall achievable tuning range, both for continuous and stepwise scans, can be more than 320\r{ }. This scheme is totally immune to intensity fluctuation and allows to engage the conventional phase-shifting imaging. It is especially suitable for real-time configuration control of 2D and 3D optical lattice potentials to study the tunneling and transport effects on cold atomic samples if a Michelson-type interferometer is used. [Preview Abstract] |
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T1.00087: Mesoscopic effects in quantum phases of ultracold quantum gases in optical lattices Lincoln D. Carr, M.L. Wall, D.G. Schirmer, R.C. Brown, J.E. Williams, Charles W. Clark We present a wide array of quantum measures on numerical solutions of one-dimensional Bose- and Fermi-Hubbard Hamiltonians for finite-size systems with open boundary conditions. Specifically, for the Bose-Hubbard Hamiltonian we calculate number, quantum depletion, local von Neumann entropy, generalized entanglement or Q measure, fidelity, and fidelity susceptibility; for the Fermi-Hubbard Hamiltonian we also calculate the pairing correlations, magnetization, charge-density correlations, and antiferromagnetic structure factor. Our numerical method is imaginary time propagation via time-evolving block decimation. As part of our study we provide a careful comparison of canonical versus grand canonical ensembles and Gutzwiller versus entangled simulations. The most striking effect of finite size occurs for bosons: we observe a strong blurring of the tips of the Mott lobes accompanied by higher depletion, and show how the location of the first Mott lobe tip approaches the thermodynamic value as a function of system size. [Preview Abstract] |
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T1.00088: Field Enhancement Cavity for Pondermotive Optical Lattices Stefan Zigo, Georg Raithel Rydberg atoms trapped in ponderomotive optical lattices (POLs) have a number of applications in atomic physics such as quantum information and computation, and high-resolution spectroscopy. Many of the effects that can be induced by subjecting highly-excited atoms to a ponderomotive optical lattice potential,$V=\textstyle{{e^2\vert E(r)\vert ^2} \over {4m_e \omega ^2}}$, require lattice depths that are larger than what can be readily created by counter-propagating, focused laser beams. In particular, spectroscopic studies of the adiabatic lattice potentials of Rydberg atoms in lattices will require potentials that are several GHz deep. Here, we explore the use of concentric optical resonators to create high-intensity, continuous (cw) standing-wave fields that will generate deep optical-lattice potentials. We have tested and characterized a concentric cavity with a finesse of about 30 using a 10W, 1064nm, single frequency, cw-laser. The cavity is stabilized by utilizing a Pound-Drever-Hall locking scheme. We will present schemes how the cavity will be used in future optical-lattice experiments. [Preview Abstract] |
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T1.00089: Dimer of Two Bosons in a One-dimensional Optical Lattice Jerome Sanders, Otim Odong, Juha Javanainen Using a Bose-Hubbard model, we theoretically examine the stationary states of two bosons in a one-dimensional optical lattice with periodic boundary conditions. A partial separation of the center-of-mass and relative motions of the two-atom lattice dimer is utilized to determine the eigenstates in a finite lattice. The eigenstates are then analyzed in the limit of an infinitely long lattice. Closed-form analytic expressions for the bound state and the dissociated states of the dimer are found. To confirm the results in momentum representation, an analogous investigation is done in position representation. Three examples for the detection of the dimer are discussed: measuring the momentum distribution of the atoms, measuring the atom number correlations at two sites, and dissociating a bound state of the dimer with a modulation of the lattice depth. [Preview Abstract] |
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T1.00090: The Development of Atomtronic Components Ronald Pepino, John Cooper, Dana Anderson, Murray Holland The ultracold atom-optical analogy to electronic systems is presented, along with the master equation formalism that is applied to this novel physical context of system-reservoir interaction. The proposed formalism lends itself quite readily to not only the study of atomtronic systems, but also transport properties of ultracold atoms in optical lattices. We demonstrate how these systems can be configured so that they emulate the behavior of the electronic diode, field effect transistor (FET), and bipolar junction transistor (BJT). The behavior of simple logic gates: namely, the AND and OR gates follow as direct consequences of the atomtronic BJTs. [Preview Abstract] |
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T1.00091: Exploring Complex Phenomena using Ultracold Atoms in bichromatic lattices Shuming Li, Indubala Satija, Charles Clark, Ana Rey With an underlying common theme of competing length scales, we study the many-body Schrodinger equation in a quasiperiodic potential and discuss its connection with the Kolmogorov-Arnold Moser (KAM) problem of classical mechanics. We propose a possible visualization of such connection in experimentally accessible many-body observables. We demonstrate those observables not only are useful probes for the three characteristic phases of the problem: metallic, Anderson and band insulator phases but in addition exhibit fingerprints of non-linear phenomena such as \textit{Arnold tongues}, \textit{bifurcations} and \textit{devil-stair} cases. Our numerical treatment is complemented with a perturbative analysis which provide insight on the underlying physics. The perturbation theory is particularly useful in illuminating the distinction between the Anderson insulator and the band insulator phases in terms of \textit{paired sets of dimerized states}. [Preview Abstract] |
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T1.00092: Resonant Dynamics of Interacting Cold Atoms in a Constant Field Chester Rubbo, Brandon Peden, Ana Rey, Murray Holland We propose to study the dynamics of strongly interacting ultracold bosons loaded at commensurate and incommensurate fillings in an optical lattice driven by a constant force field. The field is tuned resonantly with the interaction parameters providing a reduced Hilbert space for analysis at sufficiently short times. In addition, we investigate a possible non-destructive detection scheme for the atomic motion by coupling the atoms to a small-intensity cavity field and show how the dynamics in our system is reflected in the probe field. [Preview Abstract] |
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T1.00093: Number statistics of a 2D quantum gas based on in situ imaging Chen-Lung Hung, Xibo Zhang, Peter Scherpelz, Nate Gemelke, Cheng Chin Two-dimensional (2D) ultracold atomic gases exhibit intriguing many-body phenomena, including critical behavior near a quantum phase transition. We present a system for in situ imaging of a 2D cesium-133 Bose-Einstein condensate loaded into a 2D optical lattice, revealing the spatial distribution of occupancy number and its fluctuations in a trapping potential. Furthermore, by inducing three-body recombination loss, number statistics can be probed directly in this system by comparing the density profile before and after loss. These tools provide unique information on these quantum gases, including the spatial variation of number squeezing in the lattice and non-equilibrium dynamics as the lattice depth is changed. This system also holds potential for probing many-body physics beyond the superfluid to Mott insulator transition, and at deep lattice depths, fundamental problems in few-body physics. [Preview Abstract] |
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T1.00094: Interfacing Conventional and Topological Qubits in Optical Lattices Garry Goldstein, Liang Jiang, Mikhail Lukin We propose a new interface between conventional and topological qubits. The conventional qubit is encoded in the spin states of two cold atoms of a double well optical trap. The topological qubit resides in the topologically degenerate internal states of four vortices created within p-wave superfluid on a two dimensional optical lattice. The vortices are generated by Laguerre-Gaussian Laser beams propagating transverse to the lattice. We demonstrate that through three controlled tunneling interactions between the conventional and topological qubits it is possible to swap the states of the two qubits. Applications to quantum memory and computing are discussed. [Preview Abstract] |
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T1.00095: Quantum Information Processing with Two Atomic Species Confined in Independently Controlled Optical Lattices Kathy-Anne Brickman Soderberg, Arjun Sharma, Andreas Klinger, Skyler Degenkolb, Nathan Gemelke, Cheng Chin We present progress toward scalable quantum information processing using fermionic $^6$Li and bosonic $^{133}$Cs each confined in an independently controlled optical lattice. The $^6$Li atoms, loaded with one atom per site, act as quantum bits (qubits) to store information while $^{133}$Cs, loaded with one atom per one hundred sites, is a messenger bit to mediate gate operations and carry entanglement between $^6$Li qubits. We demonstrate the fabrication of identical and stable hexagonal optical lattices at 680nm for $^6$Li and 1064nm for $^{133}$Cs using a diffraction grating and common mode optics. Qubit operations are performed by spatially overlapping a messenger and qubit. This is done by phase shifting the lattices with an electro-optic modulator array that can either adiabatically shift an atom over one lattice site in 11$\mu$s, or rapidly shift the lattice in 100ns such that no atomic motion occurs. These two modes allow the messenger atom to ``step'' across the lattice to address any (distant) $^6$Li qubit. [Preview Abstract] |
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T1.00096: Yb Optical Lattice Clock Andrew Ludlow, Nathan Lemke, Yanyi Jiang, Jeff Sherman, Chris Oates Here we report on recent efforts and measurements of an optical atomic clock based on 171Yb atoms tightly confined in an optical lattice potential. Optical lattice clocks have already demonstrated performances rivaling cesium primary standards, and these young systems have further potential to be realized. We describe improvements in the short- and mid-term stability of these standards, including improvements in the frequency stabilization of the interrogation laser. We further discuss experimental realization of multi-dimensional lattice confinement, as well as various frequency measurements and comparisons of the Yb lattice clock. [Preview Abstract] |
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T1.00097: The dynamics of two-component BECs loaded in an optical lattice: truncated Wigner approximation Hyunoo Shim, Thomas Bergeman For two hyperfine states of ultracold atoms, the interspecies interaction modifies the phase diagram and the superfluid-Mott insulator transition. We study the nonequilibrium dynamics of two hyperfine states of Bose-Einstein condensates in a 1D state-dependent optical lattice with a harmonic trap and we investigate the nonadiabaticity of the phase transition as the lattice potential is modulated. Numerical simulations are performed using the multimode truncated Wigner approximation. An exact ground state is calculated by the split operator imaginary time evolution method for the Gross-Pitaevskii equation. Bogoliubov excitation modes are obtained by an exact diagonalization routine. The propagation of stochastic fields is carried out by the real-time split operator method. We intend to show the behavior of phase coherence, one body density matrix, and number fluctuation. [Preview Abstract] |
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T1.00098: Precision laser beam shaper for optical lattice quantum emulation applications Rudy Kohn, Jinyang Liang, Mike Becker, Daniel Heinzen We have developed a laser beam-shaper that uses a digital micro-mirror device (DMD) in conjunction with an error diffusion algorithm as well as an iterative correction algorithm to generate laser beams with an arbitrary intensity profile. With this device, we have generated flat-top intensity profile beams with better then 0.5{\%} rms flatness. We are in the process of implementing a controllable intensity profile optical lattice for a Bose-Hubbard gas with this beam shaper. This should allow us to carry out a precision study of the homogeneous Bose-Hubbard gas, and to circumvent problems related to sample inhomogeneity in quantum emulation. Extensions of our method might also be useful for manipulation of sample entropy and cooling, for the study of excitations, and other quantum emulation applications. [Preview Abstract] |
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T1.00099: Microscopy of a Quantum Gas in a 2D Optical Lattice Waseem Bakr, Amy Peng, Ming Tai, Ruichao Ma, Gregor Jotzu, Jonathon Gillen, Simon Foelling, Markus Greiner Ultracold quantum gases in optical lattices provide a rich experimental toolbox for simulating the physics of condensed matter systems. With atoms in the lattice playing the role of electrons or Cooper pairs in real materials, it is possible to experimentally realize condensed matter Hamiltonians in a controlled way. To realize the full potential of such quantum simulations, we have created a quantum gas microscope (NA = 0.8) which can spatially resolve the atoms in the optical lattice at the single site level, and project arbitrary potential landscapes onto the atoms by combining the high resolution optics with static holographic masks or a spatial light modulator. The high resolution microscope operates with the atoms trapped in a two dimensional optical lattice at a distance of 10 microns from a glass surface that is part of the microscope. We have experimentally verified a resolution of $\sim $ 600 nm, providing the capability to study the phase diagram of the Bose Hubbard model by measuring occupation number at individual sites. [Preview Abstract] |
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T1.00100: DEGENERATE FERMI GASES |
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T1.00101: Hartree-Fock-Bogoliubov Theory of Dipolar Fermi Gases Cheng Zhao, Lei Jiang, Xunxu Liu, Wuming Liu, Xubo Zou, Han Pu We construct a fully self-consistent Hartree-Fock-Bogoliubov theory that describes a spinless Fermi gas with long-range interaction. We apply this theory to a system of uniform dipolar fermionic polar molecules, which has attracted much attention recently, due to rapid experimental progress in achieving such systems. By calculating the anisotropic superfluid order parameter, and the critical temperature Tc, we show that, ``hign Tc'' superfluid can be achieved with a quite modest value of interaction strength for polar molecules. In addition, we also show that the presence of the Fock exchange interaction enhances superfluid pairing. [Preview Abstract] |
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T1.00102: Equation of State and Spin Transport in a Fermi Gas with Universal Interactions Ariel Sommer, Mark Ku, Andre Schirotzek, Martin Zwierlein We present experiments on the equation of state and spin transport properties of degenerate two-component Fermi gases with interactions tuned in the vicinity of a Feshbach resonance. The density distribution in an external potential directly probes the equation of state under the local density approximation. Regions of low density allow us to extract the chemical potential and the temperature using the virial expansion of the equation of state. The experimental results are compared to recent Monte-Carlo calculations. Spin transport is observed by separating the spin components of a two-component Fermi gas and measuring the evolution of the system as it returns to equilibrium. We determine the spin relaxation rate as a function of interaction strength across the Feshbach resonance and estimate the spin diffusion coefficient. [Preview Abstract] |
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T1.00103: Strongly Interacting Mixtures of Ultracold Atoms Cheng-Hsun Wu, Ibon Santiago, Jee Woo Park, Peyman Ahmadi, Martin W. Zwierlein The study of mixtures of two or more different atomic species is a new frontier in the field of ultracold quantum gases. Part of the motivation for this research lies in the interest in novel forms of superfluidity, which could for example mimic bulk nuclear matter and exotic superconductors. In this poster, we will present our experimental progress on cooling a Fermi-Fermi mixture of the fermionic Alkalis $^6$Li and $^{40}$K. The difficulty of the low natural abundance of $^{40}$K (%0.01) is typically overcome with the use of enriched, but expensive, $^{40}$K. In our approach we use two independent Zeeman slowers optimized for high atomic fluxes of non-enriched K and Li. This allows us to load 5 x $10^7$ fermionic K into a magneto-optical trap, and it also gives us access to the bosonic isotopes of $^{39}$K and $^{41}$K as possible sympathetic coolants for both $^6$Li and $^{40}$K. After producing a Bose-Einstein condensate of $^{41}$K by direct evaporation and sympathetically cooling the fermion $^{40}$K, our next goal is the production of a degenerate Fermi-Fermi mixture of $^6$Li and $^{40}$K. [Preview Abstract] |
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T1.00104: Energy spectra of small harmonically trapped few-fermion systems K. Daily, D. Blume In an effort to determine a large portion of the energy spectra of s-wave interacting harmonically trapped few-fermion systems, we pursue three distinct approaches: i) Weakly-interacting systems with small s-wave scattering lengths (i.e. $|a_s|$ small) are treated within a perturbative framework. Using hyperspherical coordinates, the perturbative energy spectra are obtained through an efficient semi-analytical formalism. ii) The energy spectrum of the three-fermion system with zero-range interactions is obtained by solving the Lippman-Schwinger equation numerically for all $a_s$. iii) The energies of larger systems are determined using the stochastic variational approach. These complimentary approaches allow for the characterization of the energy spectra of few-fermion systems. The energies can then by used to, e.g., calculate the virial expansion coefficients that determine the thermodynamics of universal Fermi gases. [Preview Abstract] |
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T1.00105: Illustrating the universal relations for a trapped four-fermion system with arbitrary s-wave scattering length K. Daily, D. Blume A two-component four-fermion system with equal masses, interspecies s-wave scattering length $a_s$, and vanishing intraspecies interactions under external spherically symmetric harmonic confinement is considered. For all calculations we employ a correlated Gaussian basis set expansion approach. We determine the energies and various structural properties of the energetically lowest-lying gaslike state throughout the crossover for various ranges of the underlying two-body potential. Extrapolating to the zero-range limit, our numerical results show explicitly [1] that the total energy, the trap energy, as well as certain aspects of the pair distribution function and of the momentum distribution are related through the so-called integrated contact intensity I($a_s$) [2]. Furthermore, it is shown explicitly that the total energy and the trap energy are related through a generalized virial theorem [3] that accounts for a nonzero range.\\[4pt] [1] D. Blume, K.M. Daily, Phys. Rev. A \textbf{80}, 053626 (2009).\\[0pt] [2] S. Tan, Ann. Phys. \textbf{323}, 2952 (2008); 2971 (2008); 2987 (2008).\\[0pt] [3] F. Werner, Phys. Rev. A \textbf{78}, 025601 (2008). [Preview Abstract] |
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T1.00106: Phase Diagram of a 1-D Spin-Imbalanced Fermi Gas Melissa Revelle, Yean-An Liao, Ann Sophie C. Rittner, Tobias Paprotta, Randall G. Hulet, S.K. Baur, E.J. Mueller Spin-imbalance in a quantum gas typically destroys superfluidity, but theory suggests that there exists an exotic superfliud state (FFLO) where pairs form with finite center-of-mass momentum. In 3D, the FFLO state is predicted to occupy only a small region of the phase diagram, while in 1D the FFLO state is pervasive\footnote{K. Yang, \textit{Phys. Rev. B.} \textbf{63}, 140511(R) (2001); G. Orso, \textit{Phys. Rev. Lett.} \textbf{98}, 070402 (2007).}. We create a spin-imbalanced Fermi gas of $^{6}$Li in 1D tubes by using a 2-D optical lattice. The central region of each tube is a partially spin-polarized gas surrounded by wings of either a fully polarized or fully paired gas depending on the spin imbalance\footnote{Y. Liao \textit{et al.}, arXiv:0912.0092 (2009).}. The phase diagram is a function of polarization and chemical potential extracted from \textit{in situ} images of the spatial distribution. This diagram is well described by finite temperature Bethe Ansatz theory, suggesting that these partially polarized regions are the 1D equivalent of FFLO states. [Preview Abstract] |
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T1.00107: Quantum Simulation using Next Generation Degenerate Fermi Gas Apparatus Kate Wooley-Brown, Florian Huber, Widagdo Setiawan, Markus Greiner Ultracold neutral atoms in optical lattices are a perfect toy model to simulate and study Hubbard model physics relevant to high temperature superconductivity and other exotic phases of matter. We present the design and construction of a novel apparatus to study these exciting condensed matter systems. We also investigate the viability of a various transport schemes to transport a quantum-degenerate Fermi gas of ultracold lithium atoms into a Science Chamber. The high optical access of the science chamber permits innovative probing and manipulation of BECs. [Preview Abstract] |
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T1.00108: ULTRACOLD COLLISIONS AND PHOTOASSOCIATION PROCESSES |
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T1.00109: Giant Feshbach resonances in $^{6}$Li+$^{85}$Rb mixtures Kirk W. Madison, Bruce G. Klappauf, Benjamin Deh, Will Gunton, Mariusz Semczuk, Zhiying Li We report on the observation of Feshbach resonances in an ultracold mixture of $^{6}$Li and $^{85}$Rb. While the Feshbach resonances in $^{6}$Li+$^{87}$Rb and $^{7}$Li+$^{87}$Rb mixtures are known to be relatively sparse and narrow, those in $^{6}$Li+$^{85}$Rb mixtures are, by contrast, numerous and wide. The experimental data are interpreted using a full coupled channels calculation which provides the energy of the least bound molecular states responsible for the observed resonances. This analysis fully characterizes the ground-state scattering properties in any combination of spin states. [Preview Abstract] |
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T1.00110: Microwave field modification of Feshbach resonances in collisions of ultra cold polar molecules Sergey Alyabyshev, Roman Krems We present a detailed analysis of Feshbach resonances in ultracold collisions of NH molecules and He atoms in the presence of superimposed magnetic and microwave laser fields. We use dressed-state formalism to describe the effects of radiation field on collision complex. We show that microwave field couplings may shift the position and significantly modify the width of magnetic Feshbach resonances, thereby making the microwave field control of ultracold molecular collisions possible. [Preview Abstract] |
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T1.00111: Role of Feshbach resonances in enhancing the production of deeply bound ultracold LiRb molecules with laser pulses Marko Gacesa, Subhas Ghosal, Robin C\^ot\'e We investigate the possibility of forming deeply bound LiRb molecules in a two-color photoassociation experiment. Ultracold $^6$Li and $^{87}$Rb atoms colliding in the vicinity of a magnetic Feshbach resonance are photoassociated into an excited electronic state. A wavepacket is then formed by exciting a few vibrational levels of the excited state and allowed to propagate. We calculate the time-dependent overlaps between the wave packet and the lowest vibrational levels of the ground state. After the optimal overlap is obtained we use the second laser pulse to dump the wave packet and efficiently populate the deeply bound ro-vibrational levels of $^6$Li$^87$Rb in the ground state. The resulting combination of Feshbach-optimized photoassociation (FOPA) with the time-dependent pump-dump approach will produce a large number of stable ultracold molecules in the ground state. This technique is general and applicable to other systems. [Preview Abstract] |
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T1.00112: Exploring Efimov physics in three spin fermionic atomic gases Jose P. D'Incao, Daniel J. Haxton, Chris H. Greene We explore three-body universal properties of ultracold collisions involving 6Li atoms in three different internal spin states. Our model is adjusted to reproduce the proper magnetic field dependence of both two-body scattering length and binding energies. We then apply the model to determine the three-body scattering properties. More specifically, we calculate three-body recombination and atom-dimer relaxation in order to test our theoretical description against the currently available experimental data, which indicate the existence of several features related to Efimov physics. [Preview Abstract] |
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T1.00113: Three-body Efimov physics near overlapping broad and narrow Feshbach resonances Fatima Anis, Yujun Wang, B.D. Esry We study three-body Efimov physics near a narrow Feshbach resonance which lies on top of a broader one. By modeling the two-body interactions with a single-channel potential, we can simultaneously reproduce the two-body physics of such overlapping resonances and make the three-body calculations tractable. Overlapping Feshbach resonances like these are not uncommon in alkali atom systems. In particular, the first experimental observation of an Efimov feature [1] utilized states in Cs that displayed this behavior. We will study Efimov physics in two regimes: (i) as a function of scattering length obtained by scanning across the narrow resonance in the presence of the large background scattering length provided by the broad resonance and (ii) as a function of scattering length obtained by scanning across the broad resonance to see the effect of the narrow resonance. In particular, we will test the limits of three-body universality in these situations by systematically investigating the three-body recombination rates. \\[4pt] [1] T. Kraemer {\it et al}, Nature {\bf 440}, 315 (2006). [Preview Abstract] |
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T1.00114: Atom-dimer scattering in an ultracold three-component mixture of $^{6}$Li Shuta Nakajima, Munekazu Horikoshi, Masahito Ueda, Takashi Mukaiyama Recently, an unexpected magnetic-field dependence of atomic loss was discovered in a mixture of three lowest-lying hyperfine states ($\vert $1$>=\vert $F=1/2, m$_{F}$=1/2$>$, $\vert $2$>=\vert $F=1/2, m$_{F}$=-1/2$>$ and $\vert $3$>=\vert $F=3/2, m$_{F}$=-3/2$>)$ of $^{6}$Li atoms. Since the first report of this loss feature, there has been an increasing interest in the loss mechanism in the context of trimer formation. We are interested in confirming the existence of the three-body bound state (Efimov trimer) and investigating mixtures of atoms in $\vert $1$>$ and dimers of $\vert $2$>-\vert $3$>$ to treat the three-component system as ``two component'' system. We prepared balanced mixtures of the atoms in $\vert $1$>$ and the dimers of $\vert $2$>-\vert $3$>$ by using adiabatic rapid passages and magnetic field sweeping. To measure the magnetic-field dependence of the atom-dimer loss rate, we held the mixture at various magnetic fields and recorded the remaining fraction of atoms in $\vert $1$>$. We found two atom-dimer loss peaks at 605 G and 685 G. Because the lower peak is expected to be due to a ``ground-state'' Efimov trimer, our finding provides the first experimental evidence for the ``ground-state'' Efimov trimer in the three-component mixture of $^{6}$Li. [Preview Abstract] |
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T1.00115: Observation of an Efimov spectrum in an atomic system Matteo Zaccanti, Benjamin Deissler, Chiara D'Errico, Marco Fattori, Mattia Jona-Lasinio, Stefan M\"{u}ller, Giacomo Roati, Massimo Inguscio, Giovanni Modugno In 1970 the Russian physicist V. Efimov predicted a puzzling quantum mechanical effect that is still of great interest today. He found that three particles subjected to a resonant pairwise interaction can join into an infinite number of loosely bound states even though each particle pair cannot bind. Interestingly, the properties of these aggregates, such as the peculiar geometric scaling of their energy spectrum, are universal, i.e. independent of the microscopic details of their components. Despite an extensive search in many different physical systems, including nuclei, atoms and molecules, Efimov spectra have long eluded observation. Here we report on the first discovery of two bound trimer states of potassium atoms very close to the Efimov scenario, which we reveal by studying three-particle collisions in an ultracold gas with tunable interaction. Our observation provides the first evidence of an Efimov spectrum and allows a direct test of its scaling behavior, shedding new light onto the physics of few-body universal systems. [Preview Abstract] |
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T1.00116: Analytic quantum dynamics approximating a system of cavity-assisted photoassociated atom-molecule Bose-Einstein condensates J. Mauricio Campuzano, Marko Zivkovic, Christopher Search We explore the quantum dynamics of photoassociation of Bose-Einstein condensed atoms into molecules using an optical cavity field. Inside an optical resonator, photoassociation of quantum degenerate atoms involves the interaction of coupled atom, molecule, and photon quantum fields. Feedback created by a high-Q optical cavity causes the cavity field to become a dynamical quantity, behavior that is linked nonlinearly to the atoms inside, where vacuum fluctuations have a stronger role than in free space. We develop and compare several methods to calculate atom-molecule conversion process dynamics. Introducing an alternate operator representation for the Hamiltonian, we derive an improved mean field theory (MFT), correcting several deficiencies in traditional MFT, and approximate solutions of the Heisenberg-Langevin (HL) equation, properly accounting for cavity field quantum noise. Comparing numerical solutions of the density matrix equations to our HL equation solutions, we also see that the latter gives an accurate description of weakly or undriven cavities where the MTF breaks down. Finally, we show squeezing occurs in the system and investigate the quantum mechanical nature of the system through a comparison of classical and non-classical correlations functions. [Preview Abstract] |
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T1.00117: Theory of photoassociation of ultra-cold trimers Viatcheslav Kokoouline, Maxence Lepers, Romain Vexiau, Nadia Bouloufa, Olivier Dulieu We present a general theory for the formation of ultracold trimers by photoassociation from an excited atom and a ground state diatomic molecule in an ultracold mixed gas containing atoms and molecules. The excited atom has a non-zero quadrupole moment, and interacts with the dimer by a quadrupole-quadrupole long-range interaction, which is attractive enough to bind trimers. We have also applied the general formalism for the multipole and dispersion asymptotic interactions to the calculation of long-range coefficients of interaction between an alkali atom (Li or Cs) in its ground or its first excited state and a molecule (Li$_2$ or Cs$_2$) in an excited rotational state. The suggested photoassociation theory can easily be generalized to the formation of tetramers from identical dimers by an RF field. [Preview Abstract] |
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T1.00118: Formation of ultracold Rb$_2$ in the ground X$^1$$\Sigma$$^+_g$ state in an optical dipole trap H.K. Pechkis, R. Carollo, M. Bellos, J. Banerjee, E.E. Eyler, P.L. Gould, W.C. Stwalley We present a study of the formation of ultracold ground-state Rb$_2$ molecules in an optical dipole trap formed by a focused CO$_2$ laser. Rubidium atoms are efficiently loaded from a magneto-optical trap (MOT) into the dipole trap, after a brief cooling and compression stage. The atomic sample is cooled significantly from 100 $\mu$K to 30 $\mu$K and the density is increased up to 10$^{12}$ cm$^{-3}$. After loading atoms into the dipole trap, a photoassociation laser is introduced to form ultracold molecules. The excited ultracold molecules spontaneously decay to the ground-state, which is subsequently detected by resonance-enhanced two-photon ionization using a pulsed dye laser. With the ultracold molecules trapped, we will pursue an experiment involving vibrational quenching of the molecules due to collisions with $^{85}$Rb atoms. With our state-selective detection, we will be able to measure the individual loss rates of each vibrational level. This work is supported by NSF. [Preview Abstract] |
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T1.00119: Effect of Nanosecond-Timescale Frequency-Chirped Light on Ultracold $^{85}$Rb$_2$ Ground-State Formation J.A. Pechkis, J.L. Carini, C.E. Rogers III, P.L. Gould We report on progress towards ultracold $^{85}$Rb$_2$ formation using frequency-chirped light on the nanosecond-timescale in a Magneto-Optical Trap (MOT). In previous work, we showed coherent control of ultracold atomic $^{85}$Rb trap-loss collisions with chirped light. In our current research, we use Resonantly-Enhanced Multi-Photon Ionization (REMPI) to directly detect ground-state $^{85}$Rb$_2$ molecules. Either positive or negative chirps, centered at a variable detuning below the \emph{D$_2$} line, sweep over 1 GHz in 100 ns. The effect of these chirps on the formation of ground-state $^{85}$Rb$_2$ in the MOT is compared to that of a CW probe laser. While initial experiments have shown an increase in atomic trap-loss with the addition of either the frequency-chirped light or the CW probe, a reduction in MOT-formed ground-state $^{85}$Rb$_2$ is seen. This work is supported by DOE. [Preview Abstract] |
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T1.00120: On certain electromagnetic field-induced interatomic interactions J.F. Babb The long-range retarded dispersion interaction potential between two neutral isotropic polarizable systems is attractive with the characteristic Casimir-Polder form $\sim - 23 \alpha_1 \alpha_2/R^7$, where $\alpha_i$ is the static electric dipole polarizability of a particle and $R$ is the intersystem separation. In contrast, the long-range retarded interaction between an electron and an ion is repulsive with form $11 \alpha/R^5$, where $\alpha$ is the ion's polarizability. Theoretically, a way to form a stable BEC with attractive $1/R$ interactions was proposed~[1]. Using external laser beams the average interatomic potential is $\sim -11 (I q^2 / c) \alpha(q)^2/R$, where $I$ is the laser intensity, $\alpha(q)$ the atomic polarizability, and $cq$ is the frequency. The connections between this (under certain conditions) ``artificial gravity-like interaction'' and more standard long-range dispersion forces are explored. In addition, similarities to ``optical binding'' are discussed. Supported in part by the NSF.\\[4pt] [1] D. O'Dell, S. Giovanazzi, G. Kurizki, and V. M. Akulin, Phys. Rev. Lett. \textbf{84}, 5687 (2000). [Preview Abstract] |
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T1.00121: Simple models of decaying Feshbach resonances Thomas Hanna, Eite Tiesinga, Paul Julienne Scattering properties of ultracold atoms can be controlled using Feshbach resonances, which can be created using magnetic, optical or radio-frequency (rf) coupling of the colliding pair to a bound state. In the lossless case, the scattering length diverges at the resonance. However, in the presence of losses the scattering length has a range limited by the rate of decay. We study decaying resonances with both rigorous calculations and simple, intuitive models. We focus on rf-induced resonances for $^{6}$Li, in which losses are created by rf coupling to several energetically lower channels. We show that creating a resonance by coupling to a broad, near-threshold molecular state can provide useful control with low rf power and manageable losses. [Preview Abstract] |
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T1.00122: Laser cooled and trapped Dy: MOT dynamics, collisions, and progress toward narrow-line cooling Seo Ho Youn, Mingwu Lu, Benjamin Lev We present details of the Dy laser cooling and trapping apparatus that has recently produced a magneto-optically (MOT) and magnetostatically (MT) trapped gas of dysprosium, a lanthanide (rare-earth) atom with an unsurpassed magnetic moment of 10 Bohr magnetons, in the 10--100 $\mu$K regime. We present details of the Dy MOT dynamics, MT inelastic collisional studies, and progress toward narrow-line cooling to the 1 $\mu$K regime. The laser cooling and trapping of highly magnetic atoms with complex level structure opens a new frontier for ultracold dipolar physics, atom chip microscopy, and quantum information processing. [Preview Abstract] |
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T1.00123: Ultracold NH-NH collisions in magnetic fields Gerrit Groenenboom, Liesbeth Janssen, Ad van der Avoird, Piotr Zuchowski, Jeremy Hutson The production of cold and ultracold molecules opens up the possibility to control chemical reactions by means of electromagnetic fields. The NH ($^3\Sigma^-$) molecule is a promising candidate for cold controlled chemistry, due to its large electric and magnetic dipole moment. We constructed high level, {\em ab initio}, singlet, triplet, and quintet interaction potentials, with analytic longe expansions for the entrance channel for chemical reaction [1]. We present preliminary quantum scattering calculations of the elastic and Zeeman relaxation cross sections from the cold (1K) down to the ultracold ($10^{-8}$ K) regime in magnetic fields ranging from $10^{-4}$ to $10^4$ gauss. We also investigate the effect of the intra- and inter-molecular spin-spin interactions. A large number of resonances over many orders of magnitude are found in elastic and inelastic cross sections. \\[4pt] [1] Liesbeth M. C. Janssen, Gerrit C. Groenenboom, Ad van der Avoird, Piotr S.~\.{Z}uchowski, and Rafa{\l} Podeszwa, J. Chem. Phys. {\bf 131}, 224314 (2009). [Preview Abstract] |
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T1.00124: Cold Chemical Reactions of CaH and Li Kyle Hardman, Mei-Ju Lu, Vijay Singh, Muir Morrison, Jonathan Weinstein We are interested in measuring chemical reactions between $^2S$ atoms and $^2\Sigma$ molecules due to the prospect of controlling the reaction rate using spin polarization. We use laser ablation and helium buffer gas cooling to simultaneously create ground state lithium atoms and CaH molecules at cryogenic temperatures with densities of $10^{12}$ and $10^8$ cm$^{-3}$, respectively. Preliminary data suggests we are able to observe chemical reactions between $^2S$ state Li and $^2\Sigma$ state CaH at 3.7 K. This data gives a preliminary reaction rate of $10^{-11}$~cm$^3$~s$^{-1}$. Progress towards controlling reaction rates with polarization will be discussed. [Preview Abstract] |
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T1.00125: Zero energy resonances in reactive scattering: anomalous temperature dependence of atom--molecule reaction rates I. Simbotin, S. Ghosal, R. C\^ot\'e We show that rate coefficients for inelastic processes---reactive, or nonreactive---in the (ultra)cold regime can be greatly affected by the presence of a resonance pole near $E=0$ in the entrance channel. This problem has been investigated previously [E. Bodo \emph{et al.}, J. Phys. B \textbf{37} (2004) 3641] but their analysis was restricted to the energy dependence of the reaction cross section for a particular case. Here, we present the general case, and we emphasize the possibility of a wide intermediate regime of temperatures where the rate coefficient has an anomalous temperature dependence; namely it increases as $1/T$ when $T$ decreases. Eventually, the temperature dependence reverts back to the standard behavior given by Wigner's law, i.e., the rate coefficient becomes constant, but this may only be recovered at extremely low $T$ (very deep into the ultracold regime). Thus, at least in some exceptional cases, most of the (ultra)cold regime could be dominated by this anomalous behavior. [Preview Abstract] |
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T1.00126: Ultracold collisions of He with highly rotationally-excited CO$_2$ W. el Qadi, B.H. Yang, P. C. Stancil, R.C. Forrey, N. Balakrishnan Elastic and rotationally inelastic processes are studied for collisions of rotationally excited CO$_2$ with He. In the ultracold limit, complex scattering lengths were computed for rotational levels up to $j=200$ using the close-coupling method and the coupled-states approximation. As illustrative examples, some cross sections are also presented. This work was motivated by recent experimental efforts to generate highly excited CO$_2$ rotational states with an optical centrifuge [1] and the possibility of translationally cooling carbon dioxide with helium buffer-gas techniques. Experiments with rotationally excited and cold CO$_2$ may be feasible as the ratio of the real to imaginary components of the scattering length exceeds $\sim$30 for $j=200$. \\[4pt] [1] A. S. Mullin, L. Yuan, S. Teitelbaum, and A. Robinson, APS Bulletin, DAMOP Abstract E1.00016 (2009). [Preview Abstract] |
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T1.00127: Tunneling probability: an evaluation of different approximations Ming Li, Constantinos Makrides, Bo Gao Before the recent developments in the quantum-defect theory\footnote{B. Gao, Phys. Rev. A \textbf{78}, 012702 (2008).} and the related analytic solutions for $1/r^n$ type of long-range potentials, there were virtually no exact result of tunneling for physically realistic systems, which made the evaluation of different approximations, such as the ubiquitous semiclassical approximation, difficult. By comparing with the exact analytic results of tunneling for $-1/r^6$ and $-1/r^4$ types of potentials, we carefully evaluate the validity of the semiclassical and the top-of-barrier\footnote{S. J. Ward and J. H. Macek, Phys. Rev. A \textbf{62}, 052715 (2000).} approximations for tunneling through the angular momentum barrier in atom-atom, ion-atom, and electron-atom interactions. [Preview Abstract] |
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T1.00128: Full-dimensional quantum dynamics calculations of H$_2-$H$_2$ collisions Balakrishnan Naduvalath, Goulven Quemener, Robert C. Forrey, Phillip Stancil We report quantum dynamics calculations of rotational and vibrational energy transfer in collisions between two para-H$_2$ molecules over collision energies spanning from the ultracold limit to thermal energies. Results obtained using a recent full-dimensional H$_4$ potential energy surface (PES) developed by Hinde [J. Chem. Phys. {\bf 128}, 154308 (2008)] are compared with those derived from the BMKP PES [J. Chem. Phys. {\bf 116}, 666 (2002)]. For vibrational relaxation of H$_2(v=1,j=0)$ by collisions with H$_2(v=0,j=0)$ as well as rotational excitations in collisions between ground state H$_2$ molecules, the PES of Hinde is found to yield results in better agreement with available experimental data. However, for highly efficient near-resonant rovibrational transitions that conserve the internal rotational angular momentum, both PESs yield similar results. In the absence of the near-resonance mechanism vibrational relaxation is driven by the anisotropy of the potential energy surface. [Preview Abstract] |
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T1.00129: Recent progress in the computational ultracold three-body problem W. Blake Laing, Yujun Wang, B.D. Esry We have worked to improve the numerical solution of the three-body Schr\"odinger equation for ultracold collisions. In particular, we have evaluated possible improvements in the representation of the wavefunction, more efficient algorithms, and the use of hardware acceleration with graphical processing units (GPUs). We will report our progress on all fronts --- both positive and negative. [Preview Abstract] |
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T1.00130: Collisions in an $^{85}$Rb MOT via the 5S-5D Long Range Molecular Potential Truman Wilson, Jacob Roberts We report an enhancement of two-body collisional losses induced via a two step excitation up to the 5S-5D long range molecular potential in an $^{85}$Rb MOT. Excitation up to this state produces a flux of excited state atom pairs to close internuclear separations due to the long lifetime of this state. At these close separations, the atoms decay down to steeper potential curves, accelerating the pair out of the trap. Measurements of the loss rates as a function of laser intensities allow the identification of the loss channel involved in the collisions, and calculations of Landau-Zener avoided crossings explain the observed saturation effects. We found a two-body loss coefficient of 2.05 $\pm$ 0.06 (statistical) $\pm$ 1.0 (systematic) x 10$^{-10}$ cm$^3$/s for our conditions. [Preview Abstract] |
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T1.00131: Cold three-body collisions of H with alkali atoms Yujun Wang, J.J. Hua, J.P. D'Incao, B.D. Esry We have studied three-body collisions involving some commonly used alkali atoms. In particular, for spin-polarized H+H+Li, H+H+Na, H+H+K, H+H+Rb, and H+H+Cs systems, we have calculated the three-body recombination rates, elastic atom-diatom cross sections, and three-body bound state energies. We solved the three-body Schr{\"o}dinger equation in the hyperspherical adiabatic representation using realistic two-body potentials to build the three-body interactions. The calculations cover energies up to 0.5 Kelvin and partial wave contributions up to $J$=$5$. [Preview Abstract] |
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T1.00132: QUANTUM COMPUTATION |
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T1.00133: Non-monotonicity in the quantum-classical transition for the harmonic oscillator Andrew C. McClung, Tyler E. Keating, Adam T.C. Steege, Arjendu K. Pattanayak The negative volume of a Wigner function can be considered a measure the degree of quantumness of a system. In the absence of decoherence, this measure of quantumness of an harmonic oscillator increases with the energy eigenstates $n$. This seeming disagreement with the correspondence principle is of course resolved when considering decoherence. Interestingly, when any decoherence is introduced, an eigenstate $n_{peak}$ with `maximal quantumness' results so that the quantum-classical transition is non-monotonic. The value of $n_{peak}$ decreases with time and strength of environmental coupling. [Preview Abstract] |
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T1.00134: Experimental non-classicality of an indivisible system Radek Lapkiewicz, Peizhe Li, Christoph Schaeff, Nathan Langford, Sven Ramelow, Marcin Wiesniak, Anton Zeilinger In Quantum Mechanics, in contrast to other physical theories, not all properties can be measured simultaneously (the Heisenberg Uncertainty Principle is a manifestation of this fact). An interesting question arises as to whether there can be a joint probability distribution describing the outcomes of all possible measurements, allowing a quantum system to be mimicked by classical means. We show the first experimental evidence that even for a single three-level quantum system no such classical model can exist that correctly describes the results of a simple set of measurements as suggested by Klyachko et al. [PRL 101, 020403 (2008)]. This is the most simple system where such a contradiction is possible. It is also indivisible and as such cannot contain entanglement. Our result sheds new light on the conflict between quantum and classical physics and provides insight into the limitations of simulating quantum systems using, hidden or not, classical information. [Preview Abstract] |
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T1.00135: Calculation of the Unitary part of the Bures Measure for N-level Quantum Systems Renan-Andres Cabrera-Lafuente, Herschel Rabitz We calculate the analytical form of the unitary part of the Bures measure in terms of the canonical coset parametrization and show how to obtain expressions made of the product of Euclidean balls. [Preview Abstract] |
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T1.00136: Quantum computing with Bose--Einstein condensate Bragg interferometry Mark Edwards, Charles W. Clark, Jeffrey Heward, Brandon Benton Quantum computers use the interferences of different computational paths to enhance correct outcomes. Quantum computation can be viewed as multiparticle computational interference~[1]. We describe how quantum circuits can be mapped to interferometry experiments performed on BECs using Bragg pulses. We extend an approach originally developed to model Bragg interferometry of BECs~[2], to describe new interferometers based on quantum information concepts. This approach follows ideas recently introduced in neutron interferometry~[3]. Using techniques that have been well calibrated by experiments in conventional BEC interferometry~[2], we model the experiments associated with some simple quantum circuits using the prototyping method mentioned above. We prototype extensions to standard Mach-Zehnder configurations, analogous to the four-blade designs of neutron interferometry.\\[4pt] [1] R. Cleve, Proc. R. Soc. Lond. A {\bf 454} 339 (1998) et al.\newline [2] J. E. Simsarian, {\em et al.}, {\em Phys. Rev. Lett.} {\bf 85}, 2040 (2000) \newline [3] D. A. Pushin, M. Arif, and D. G. Cory, {\em Phys. Rev. A} {\bf 79}, 053635, (2009) [Preview Abstract] |
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T1.00137: Experimental controls of a superposition of coherent states Makoto Takeuchi, J.S. Neergaard-Nielsen, Hiroki Takahashi, Kentaro Wakui, Masahiro Takeoka, Kazuhiro Hayasaka, Masahide Sasaki We have generated Schr\"odinger cat states of coherent light by photon subtraction [K. Wakui et al., Opt. Express 15, 3568 (2007), H. Takahashi et al., Phys. Rev. Lett. 101, 233605 (2008)]. By using the cat states as ancillas, quantum computations in the coherent state basis can be realized [T. C. Ralph et al., Phys. Rev. A 68, 042319 (2003)]. Related to that idea, we have proposed a method to control the superposition coefficients of two phase-opposite coherent states [M. Takeoka and M. Sasaki, PRA 75, 064302(2007)]. It is based on a squeezer of coherent vacuum, a beam splitter, a displacement operation, and an on/off-type photon detector. The superposition coefficients can be controlled by properly setting the complex amplitude of the displacement. In this presentation, we report on the experimental demonstration of our proposal. To measure the superposition coefficients, we performed quantum state reconstruction with homodyne tomography. These experimental results agree well with our theoretical expectations. Quantum computation in the coherent state basis will work as the collective quantum decoder for coherent optical communications, which can attain the capacity of lossy bosonic channels [V. Giovannetti et al., Phys. Rev. Lett. 92, 027902(2004)]. [Preview Abstract] |
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T1.00138: Universal properties in ultracold ion-atom interactions Bo Gao We present some of the universal properties in ion-atom interaction derived from a newly formulated quantum-defect theory for $-1/r^4$ type of long-range interaction. For bound states, we present the universal spectrum, namely the equivalent of the Rydberg formula, for ion-atom systems. For scattering, we introduce the concept of universal spectrum for scattering resonance positions as a generalization of the universal bound spectrum. Among many conclusions that can be drawn from the universal spectrum, we show that there exists a critical energy, $B_c(l)$, that separates the scattering resonances with positive widths below it, and scattering resonances with negative widths above it. This concept, and many others introduced here including the concept of universal resonance spectrum, are expected to be generally applicable to all quantum systems with long-range interaction of the type of $-1/r^n$ with $n>2$. [Preview Abstract] |
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T1.00139: Generation of Bi-partite Polarization Correlation using Coherent States for Quantum Communication Viktor Bollen, Yong Meng Sua, Kim Fook Lee We present a novel scheme to generate bi-partite polarization correlation using coherent states for quantum communication. The scheme can be used for entanglement based quantum cryptography, where the bi-partite correlation will be protected by quantum noise. We perform experimental measurement on two independent coherent states with low mean photon numbers. A coherent state with polarization H is mixed with another coherent state with polarization V through a beam splitter. Polarization correlation is manipulated by using a quarter wave plate and a linear polarizer at each output of the beam splitter. The product signal obtained from the output modes contains bi-partite correlation and other noise terms. We obtain the bi-partite correlation function by employing mean-value measurement based on Stapp's formulation on the product signal, where the noise term is then averaged to zero due to randomness of quantum phase noise. The bi-partite correlation obtained by using two coherent states is quantum correlation because coherent states with low mean photon numbers are involved and the correlations are protected by randomness of quantum noise as inherited by mean photon number fluctuation and its associated phase fluctuation. Preparations for four types of coherent-state polarization correlation functions are also outlined. [Preview Abstract] |
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T1.00140: Collisional decoherence of internal state superpositions in a trapped ultracold gas Christopher Hemming, Roman Krems We analyze the temperature-dependent rate of decoherence of superpositions of internal states of trapped molecules due to collisions with ultracold buffer gas particles. Our analysis is applicable for an arbitrary bath/tracer particle mass ratio. Both elastic and inelastic collisions contribute to decoherence. We obtain an expression relating the observable decoherence rate to pairwise scattering properties, specifically the scattering lengths and low-temperature scattering amplitudes. We consider the dependence on the bath/tracer particle mass ratio for the case of light bath and heavy tracer particles. The expressions obtained may be useful in low-temperature applications where accurate estimates of decoherence rates are desirable. The results suggest a method for determining the scattering lengths of atoms and molecules in different internal states by measuring decoherence-induced damping of coherent oscillations. [Preview Abstract] |
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T1.00141: ABSTRACT WITHDRAWN |
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T1.00142: Algorithmic Cooling of a Quantum Simulator Dvir Kafri, Jacob Taylor Adiabatic preparation is a common technique for obtaining the ground state of an unknown quantum mechanical system, by slowly varying the system Hamiltonian. A principle disadvantage is that its timing scales with the gap energy of the intermediate Hamiltonian, not with the final Hamiltonian. We present an alternative algorithm for cooling an arbitrary system of qubits, through interaction with a small number of ``bath'' qubits. We specify bounds for the algorithm parameters, and show that its timing scales only with the specified system's gap energy. We derive a Markov chain model for the algorithm's statistical performance, and compare the model's prediction to simulated results on a frustrated three-spin system. We further discuss possible experimental applications. [Preview Abstract] |
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T1.00143: Numerical Solution of Radial Biquaternion Klein-Gordon Equation Vic Christianto, Florentin Smarandache We have argued that biquaternionic extension of Klein-Gordon equation has solution containing imaginary part, which differs appreciably from known solution of KGE. In the present article we present numerical /computer solution of radial biquaternionic KGE (radialBQKGE); which differs appreciably from conventional Yukawa potential. Further observation is of course recommended in order to refute or verify this proposition. [Preview Abstract] |
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T1.00144: Statistics of quantum inteference in random positive maps Daniel Braun, Ludovic Arnaud We study the statistics of quantum interference for completely positive maps. The ensemble of maps is obtained from the unitary propagation of a larger system, with a propagator drawn from the Circular Unitary Ensemble (CUE), and tracing out environmental degrees of freedom. We calculate analytically the mean interference and its second moment for finite dimensional quantum systems interacting with a simple environment consisting of one or several spins (qudits), based on a measure of quantum interference introduced in (1). We show that the mean interference decays with a power law as function of the dimension of the Hilbert space of the environment, and determine that power as function of the temperature of the environment. The width of the interference distribution decays with a power law both as function of the dimension of the Hilbert space of the system and the Hilbert space of the environment. For sufficiently small system sizes we obtain the full interference distribution numerically. \\ (1) D. Braun and B. Georgeot, Phys.~Rev.~A {\bf 73}, 022314 (2006)\\ (2) L. Arnaud and D. Braun, Phys.~Rev.~A {\bf 80}, 062329 (2009) [Preview Abstract] |
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T1.00145: Quantifying the quantum correlations in light-harvesting complexes Sai Vinjanampathy, Kamil Bradler, Mark Wilde, Dimitri Uskov Biological systems have been of recent interest for the role that quantum correlations may play for functionality or in evolution. One such biological phenomenon under study is the photosynthesis of certain organisms, for instance low light adapted green sulfur bacteria. The Fenna-Matthews-Olson (FMO) protein complex is a biological light harvesting complex that is found in such systems. It has drawn considerable attention as a template to understand the role of quantum correlations. Many measures exist that can be employed to characterize quantum correlations. One such measure, quantum discord, captures all non-classical correlations that are present in the system. Since discord may be robust against various models of decoherence, there is further interest in understanding whether there is quantum discord present in the FMO complex. The first picosecond is relevant for the transfer of excitation. We study many related measures of quantum correlations such as quantum discord, mutual information and relative entropy of entanglement to understand the nature of correlations and the timescales over which they persist in the FMO complex. [Preview Abstract] |
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T1.00146: Efficient Approaches to Universal and Non-Universal Topological Quantum Computation Haitan Xu, Jacob Taylor In topological quantum computation, information is encoded non-locally in exotic quasiparticles called anyons, and quantum gates are carried out by braiding the anyons in (2+1)-dimensional space-time. Universal topological quantum computation can be carried out by a universal set of quantum gates composed of single-qubit gates and controlled-phase gate and more efficiently together with controlled-controlled-phase gate. In this poster we show a unified scheme of encoding and computing for both universal and non-universal topological quantum computation with SU(2)$_k$ anyon models. We further give explicit construction of quantum gates, especially the controlled-controlled-phase gate, for universal topological quantum computation. Consequences of these ideas for the detection and correction of errors in topological quantum computation will be explored. [Preview Abstract] |
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T1.00147: Generic Two-Photon (Two-Qubit) Gates Implemented by Number-Resolving Photodetection Dmitry Uskov Existing theoretical results on measurement-induced two-qubit photonic gates with number-resolving photodetection [1] are limited to only the controlled-NOT gate (Knill et al Nature \textbf{409}, 46-52 (2001)). We use numerical optimization techniques (Uskov et al PRA \textbf{79}, 042326 (2009)), to find optimal schemes implementing arbitrary two-qubit entangling gates, represented by generic points in the Weyl chamber of Cartan KAK decomposition of the SU(4) group (Khaneja et al, Chem. Phys. \textbf{267, }11 (2001)). We find that while any two-qubit controlled-U gate, including CNOT and CS, can be implemented using two ancilla photons with success probability 0.05 $<$ S $\le $ 2/27, a generic SU(4) operation requires three unentangled ancilla photons. Our study indicates that direct implementation of a generic SU(4) gate using an integrated optical circuit offers an order of magnitude increase in the success probability and two-fold reduction in overhead ancilla resources compared to standard triple-CNOT and double-B gate decompositions. Our results are consistent with previous work on the optimization of the Deutsch-Toffoli gate, where direct implementation of this three-qubit operation was shown to be four orders of magnitude more efficient than six-fold decomposition into CNOT gates (Uskov et al, arXiv:0908.2482v1). [Preview Abstract] |
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T1.00148: RYDBERG ATOMS II |
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T1.00149: The Influence of Stray Fields on the Ionization of Rydberg atoms at Metallic Surfaces Dennis Neufeld, Yu Pu, F. Barry Dunning The effect of local surface electric (``patch'') fields on the ionization of xenon Rydberg atoms at metallic surfaces is examined. The patch fields are determined from measurements of the potential variations across the target surfaces using Kelvin probe force microscopy. These measurements are used in conjunction with a simple over-the-barrier model of ionization to predict the surface ionization characteristics for Rydberg atoms with a range of different $n$ and angles of incidence. These predictions are in good agreement with experimental measurements demonstrating the important role that patch fields play during Rydberg atom-surface interactions and suggesting that such interactions can provide a sensitive probe of stray fields at surfaces. These techniques are extended to lithographically patterned structures comprising two sets of interleaved ``comb-like'' electrodes to which different potentials can be applied. This allows control of the surface patch fields and direct study of their effects. [Preview Abstract] |
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T1.00150: Microwave spectroscopy of high-L Rydberg states of nickel Mark D. Lindsay, Julie A. Keele, Shannon L. Woods, Stephen R. Lundeen High-L non-penetrating Rydberg levels of nickel display a fine structure pattern consisting of six levels for each value of L. This pattern was studied recently with the optical RESIS technique, determining initial values of the quadrupole moment and polarizabilities of the $^{2}$D$_{5/2}$ ground state of Ni$^{+}$ [1]. Measurements are now in progress using the microwave RESIS technique [2], which promises much more precise measurements of the fine structure and of the related core properties, including the permanent hexadecapole moment.\\[4pt] [1] Julie A. Keele, et. al., to be published, Phys. Rev. A\\[0pt] [2] M.E. Hanni, et. al., Phys. Rev. A 78, 062510 (2008) [Preview Abstract] |
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T1.00151: Bound by reflection: Formation of ultralong range Rydberg molecules Weibin Li, Jovica Stanojevic, Thomas Pohl, Jan-Michael Rost Recent experiments have provided evidence for the existence of an exotic type of molecule arising entirely from low-energy scattering of a Rydberg electron and a nearby ground state atom. The resulting molecular potential reflects the highly oscillatory character of the Rydberg atom's wavefunction and leads to binding at extremely long range of several thousand Bohr radii. Here we demonstrate the existence of a wide spectrum of molecular lines that originate from two different sources: a Rydberg trimer formed in a single photon association and a series of excited dimer states which are bound by a so far unknown mechanism $-$ namely internal quantum reflection. Adapting scattering-theory concepts to long-range bound states, we thoroughly examine this new binding mechanism and explore schemes for coherent control of the molecular stability. [Preview Abstract] |
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T1.00152: Properties of heavy Rydberg ion-pair states formed in collisions between K($n$p) Rydberg atoms and attaching targets M. Cannon, C.H. Wang, F.B. Dunning The properties of heavy-Rydberg ion-pair states produced through electron transfer in thermal-energy collisions between K($n$p) Rydberg atoms and molecules that attach low-energy electrons are investigated. Collisions with targets that undergo non-dissociative attachment create bound ion pairs of the type K$^{+}\cdot \cdot \cdot $XY$^{-\ast }$, where XY$^{-\ast }$ indicates a vibrationally-excited anion. Measurements show that the lifetimes of such ion pairs is limited to a few microseconds by mutual charge transfer, which leads to separation as neutrals, and by dissociation induced by conversion of internal energy in the negative ion into translational energy of the ion pair. Such dissociation is not possible for ion-pair states that involve atomic negative ions such as can be formed through collisions with targets that undergo dissociative attachment. Measurements show the lifetimes of such bound ion pairs are very long. [Preview Abstract] |
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T1.00153: Weakly Bound Rydberg-Dipole Molecules Seth Rittenhouse, Hossein Sadeghpour We predict a class of long-range Rydberg molecules consisting of a Rydberg atom and a tightly bound polar molecule. Long-range Born-Oppenheimer potentials that describe the interaction in these molecules are presented. These potentials and fall into two classes which produce different polarization directions of the dipolar molecule with respect to the positively charged Rydberg core. The large overall dipole moment of the Rydberg atom-dipole system may allow for control of molecular polarization using relatively small electric fields. Different experimental scenarios and atom-molecule mixtures are discussed. [Preview Abstract] |
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T1.00154: Effects of Electric Fields on Rydberg-Rydberg Long-Range Interaction and Formation of Stable Macrodimer Bound States Nolan Samboy, Jovica Stanojevic, Robin C\^ot\'e We study long-range interactions between two Rydberg atoms under the effects of a small electric field. We show that long-range potential wells are relatively unaffected by the presence of the electric field (i.e. they are stable when compared to their zero-field counterparts). We also show that particular wells can sustain several bound states, with lifetimes limited by the lifetimes of the Rydberg atoms making them. We calculate properties of these molecular bound states and present theoretical photoassociation rate coefficients for the formation of these macrodimers starting from various atomic Rydberg states. [Preview Abstract] |
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T1.00155: Half-cycle-pulse-train Induced State Redistribution of Rydberg Atoms Andrew Speck, Pankaj Mandal We report on population transfer between low-lying Rydberg states independent of the initial state realized using a train of half-cycle pulses with pulse durations much shorter than the classical orbital period. We demonstrate experimentally the population transfer from initial states around $n=50$ with 10\% of the population de-excited down to $n<40$ as well as up to the continuum. This is a demonstration of a state-independent de-excitation technique applicable to the currently produced state distribution of antihydrogen. The measured population transfer matches well to a model of the process for one-dimensional atoms. [Preview Abstract] |
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T1.00156: Imaging of spatial correlations of Rydberg excitations in cold atom clouds Andrew Schwarzkopf, Rachel Sapiro, Georg Raithel Previously, Rydberg excitation blockades have been shown to cause a saturation of Rydberg excitation numbers in atom samples and a narrowing of the excitation number statistics, and they have been employed in quantum information experiments. In the experiment described in this poster, it is planned to measure structures in the Rydberg pair correlation function predicted in.\footnotemark[2] To achieve sufficient spatial magnification, we use the principle of field ion microscopy. A tungsten tip is placed close to a cold atom cloud in which several Rydberg excitations are prepared using a narrow-linewidth laser. To read out the sample, the tip voltage is suddenly switched to a high value. The Rydberg atoms are field-ionized, and the resultant ions are projected onto a nearby position-sensitive detector. All components of this experiment are operational, as will be shown on this poster. Progress towards the imaging of spatial correlations of excitations will be discussed. \footnotetext[2]{ F. Robicheaux and J. Hernandez, ``Many-body wave function in a dipole blockade configuration," Phys. Rev. {\bf A 72}, 63403, 1-4 (2005).} [Preview Abstract] |
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T1.00157: Scaled Energy Spectroscopy of Collisionally Perturbed Potassium Rydberg States Matthew Len Keeler, William Setzer We will present preliminary results on the recurrence spectroscopy (or scaled energy spectroscopy) of highly-excited potassium in the presence of collisional perturbations. Recurrence spectroscopy, with the aid of closed orbit theory, has produced useful insights into the semi-classical description of non-hydrogenic spectral features of excited atoms in external fields. We demonstrate how to apply recurrence spectroscopy to the Stark spectrum of potassium subject to collisional line-shift and line-broadening. When krypton gas is added to the system the absorption spectrum experiences line broadening, differential line shifts, and state mixing. With an appropriately modified energy scale, perturbations of the absorption spectrum become meaningful features within the scaled-energy spectrum. New features found within the recurrence spectra can then, with semi-classical closed orbit theory, be interpreted in terms of classical decoherence, elastic and inelastic collisions. [Preview Abstract] |
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T1.00158: EXPERIMENTS WITH ANTIMATTER |
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T1.00159: Monte Carlo modeling of Surko type positron traps Milovan Suvakov, Srdjan Marjanovic, Ana Bankovic, Zoran Petrovic, Stephen Buckman, Joan Marler Using comprehensive cross section sets for e$^{+}$ - N$_{2}$ and e$^{+}$ - CF$_{4}$ interaction and a Monte Carlo code, we have modeled several configurations of collisional Penning-Mamberg-Surko positron trap. The static models include three stage potential well configuration. The dynamic model employs a time dependant electric potential that corresponds to the loading, cooling and dumping stages of the trap operation. We analyzed the type and frequency of collisions in different parts of the trap and mechanisms of positron losses. The results include overall trapping efficiency and the parameters of the outgoing beam such as positron energy distribution and the width of the beam. The goal of the simulation is to optimize the parameters of the trap (buffer gas pressures, dimensions of the chamber, electric potential shape, duration of different operation stages, etc.). In addition we can include realistic magnetic field and gas density distributions and investigate how those affect the performance of the trap. [Preview Abstract] |
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T1.00160: Positron scattering with molecules of biological relevance James Sullivan, Casten Makochekanwa, Dan Slaughter, Peter Caradonna, Adric Jones, Wade Tattersall, Stephen Buckman, Ana Bankovic, Zoran Petrovic, Kate Nixon, Michael Brunger Positron annihilation provides the basis of Positron Emission Tomography (PET), a medical imaging technology now in widespread use throughout the world. Understanding radiation dose rates is crucial in applying this technique, and current methods are based on models assuming the positron behaves identically to an electron, as well as lacking the real physics in the scattering processes as represented by measured scattering cross sections. At the Australian Positron Beamline Facility we have undertaken a program of measurements investigating positron scattering from biologically relevant molecules, to form the basis of a new model of dosimetry in PET scans. Measurements of positron scattering from water and formic acid will be presented, including the first measurements of positronium formation cross sections for these targets. [Preview Abstract] |
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T1.00161: Deuteration studies of resonant positron annihilation on hydrocarbon molecules J.R. Danielson, J.J. Gosselin, C.M. Surko Annihilation on molecules is enhanced by positron attachment to the molecule via the excitation of vibrational Feshbach resonances (VFR).\footnote{J.~A.~Young and C.~M.~Surko, {\it Phys.~Rev.~A} {\bf 77}, 052704 (2008).}$^,$\footnote{J.~A.~Young and C.~M.~Surko, {\it Phys.~Rev.~A} {\bf 78}, 032702 (2008).} While there is now a quantitative theory of mode-based VFR in small molecules,\footnote{G.~F.~Gribakin and C.~M.~R.~Lee, {\it Phys.~Rev.~Lett.} {\bf 97}, 193201 (2006).} a number of open questions remain. We discuss experiments to address these outstanding issues using partial deuteration of hydrocarbons to change the vibrational mode frequencies without changing the electronic structure or positron binding energy. One topic is the observation of combination- and overtone-mode VFR in small molecules (e.g., C$_2$H$_2$, C$_2$H$_4$, NH$_3$, and methanol).\footnote{J.~A.~Young, {\it et. al.}, {\it Phys.~Rev.~A} {\bf 77}, 060702(R) (2008).} Another is that the large increase in annihilation in larger molecules appears to proceed by intramolecular vibrational energy redistribution (IVR), resulting in annihilation rates $\propto$ $N^4$, where $N$ is the number of atoms in the molecule$^2$. Partial deuteration of butane is used to explore the origin of this dependence. Deuterium-substitution experiments with ethane and cyclopropane to study the transition to IVR will also be discussed. [Preview Abstract] |
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T1.00162: Positron binding to molecules C.M. Surko, J.R. Danielson, J.J. Gosselin \def\appgteq{\mathrel{\vcenter{\hbox{$\buildrel{\textstyle >}\over{\sim}$}}}} Positron annihilation on molecules as a function of incident positron energy exhibit vibrational Feshbach resonances (VFR).\footnote{J.~A.~Young and C.~M.~Surko, {\it Phys.~Rev.~A} {\bf 77}, 052704 and {\bf 78}, 032702 (2008).} The energy differences between the vibrational modes and the VFR provide a measure of the positron-molecule binding energy, $\epsilon_b$. Measurements of $\epsilon_b$ for 30 molecules are now available from this procedure and from comparison with theoretical spectra in the case of very small binding energies.$^2$ The dependence of $\epsilon_b$ on molecular parameters can be expressed as $\epsilon_b = 12.4(\alpha + 1.6\mu + 2.4N_\pi - 5.6)$ [meV], where $\alpha$ is the molecular dipole polarizability, $\mu$ is the permanent dipole moment, and $N_\pi$ is the number of $\pi$ bonds in aromatic molecules.\footnote{J.~R.~Danielson, J.~A.~Young, and C.~M.~Surko, {\it J.~Phys.~B} {\bf 42}, 235203 (2009).} Insights into chemical trends from this analysis will be discussed. A key outstanding goal is to measure $\epsilon_b$ for molecules that are sufficiently small and simple that $\epsilon_b$ can be calculated theoretically. The empirical formula is used to identify candidate molecules. New measurements of $\epsilon_b$ for CS$_2$ (predicted $\epsilon_b \appgteq 40$ meV) will be discussed. [Preview Abstract] |
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T1.00163: Ionization and excitation in collisions between antiprotons and hydrogen atoms Thomas Winter Coupled-state cross sections have been determined for ionization and excitation in intermediate (keV)- energy collisions between antiprotons and hydrogen atoms using some of the same double-center Sturmian bases as were recently used for proton projectiles\footnote{T. G. Winter, Phys. Rev. A {\bf 80}, 032701 (2009).}. The use of a double-center basis for antiproton projectiles, in spite of there being no capture channels, was suggested and carried out by Toshima with a large Gaussian basis\footnote{N. Toshima, Phys. Rev. A {\bf 64}, 024701 (2001).}. The present results for ionization will be compared with the double-center results of Toshima and the single-center results of Igarashi \textit{et al.}\footnote{A. Igarashi, S. Nakazaki, and A. Ohsaki, Phys. Rev. A. {\bf 61}, 062712 (2000).} and McGovern \textit{et al.}\footnote{M. McGovern, D. Assafr\~{a}o, J. R. Mohallem, C. T. Whelan, and H. R. J. Walters, Phys. Rev. A {\bf 79}, 042707 (2009).}, and the crosssections for excitation of individual states up to $3d$ will be compared to the numerical results of Sakimoto \footnote{K. Sakimoto, J. Phys. B {\bf 33}, 5165 (2000).}. [Preview Abstract] |
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T1.00164: Binding energy and geometry of e$^+$Na Janine Shertzer, S.J. Ward We calculate the non-adiabatic binding energy and geometry of the weakly bound state of e$^+$Na. We use the Peach model potential to describe the e$^+$-Na$^+$ and e$^-$-Na$^+$ interactions and solve the effective three-body Schr\"odinger equation with the finite element method. Because the model potential gives rise to three spurious states (corresponding to 1s, 2s, and 2p), the true non-adiabatic ground state of e$^+$Na is embedded in a dense spectrum of spurious states. We developed a technique for extracting the correct ground state for e$^+$Na, even when the energy is nearly degenerate with a spurious level. This is the first calculation to include the quadrupole term in the polarization potential. [Preview Abstract] |
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T1.00165: The Binding Energy of PsH D. Woods, S.J. Ward, P. Van Reeth In response to proposed measurements of Ps scattering by the St.~Olaf's positron experimental group [1], we have begun a theoretical investigation of Ps scattering from simple atoms. For our first step of this investigation, we have computed the binding energy of the fundamental four-body Coulomb system, PsH. We have used a very flexible trial function of Hylleraas form which includes all inter-particle distances. Our most accurate value of the binding energy compares favorably with a previous calculation that also used Hylleraas functions [2] and with the most accurate calculation to-date which used explicitly correlated Gaussians [3]. \\[4pt] [1] Jason Engbrecht, {\it Private communication}, (2008).\\[0pt] [2] Zong-Chao Yan and Y.~K.~Ho, Phys.~Rev.~A {\bf 59}, 2697 (1999).\\[0pt] [3] Sergiy Bubin and Ludwik Adamowicz, Phys.~Rev.~A {\bf 74}, 052502 (2006). [Preview Abstract] |
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T1.00166: EXPERIMENTAL TECHNIQUES |
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T1.00167: Creation of Arbitrary Spectra with an Electro-Optical Modulator C.E. Rogers III, J.L. Carini, J.A. Pechkis, P.L. Gould We use a waveguide-based electro-optical phase modulator, in conjunction with a nanosecond-timescale arbitrary waveform generator, to produce an arbitrary pattern of sidebands. A linear voltage ramp applied to the modulator changes the optical phase linearly in time. This gives a frequency shift equal to the time derivative of the phase. A repeated sequence of such ramps with differing slopes thus generates a set of sidebands. The time and frequency resolutions are restricted by Fourier considerations. There are also limitations due to the maximum phase change achievable with the modulator and the finite speed of the arbitrary waveform generator. Such multi-line spectra, with sideband spacings in the 100 MHz range, may find use in optical pumping and efficient excitation in multi-level systems. This work is supported by DOE. [Preview Abstract] |
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T1.00168: Increasing Laser Stability with Improved Electronic Instruments Daylin Troxel, Aaron Bennett, Christopher J. Erickson, Tyler Jones, Dallin S. Durfee We present several electronic instruments developed to implement an ultra-stable laser lock. These instruments include a high speed, low noise homodyne photo-detector; an ultrahigh stability, low noise current driver with high modulation bandwidth and digital control; a high-speed, low noise PID controller; a low-noise piezo driver; and a laser diode temperature controller. We will present the theory of operation for these instruments, design and construction techniques, and essential characteristics for each device. [Preview Abstract] |
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T1.00169: Interference-filter-stabilized external-cavity diode laser Lauren Levac, Lisa Hardy, Thad Walker We present the design and characterization of an external cavity diode laser using two commercial interference filters that take the place of the common diffraction grating for mode selection. An extension of a single custom filter design [1], our method also includes a half-wave plate and polarizing beam splitter for fine adjustment of the feedback and out-coupling. We will present characterization of the laser.\\[4pt] [1] X. Baillard, et al., Optics Communications 266 (2006) 609--613 [Preview Abstract] |
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T1.00170: An Auto-Lock Laser System for Long Term Frequency Stabilization Robert Berthiaume, Andrew Vorozcovs, A. Kumarakrishnan We have developed a compact, digitally controlled system to automatically stabilize the frequency of an external cavity diode laser to an atomic resonance. The key component of the system is a low-cost single-board computer with A/D and D/A capability that acts as a specialized lock-in amplifier. The system performs pattern matching between Doppler-free peaks obtained by scanning the laser frequency and reference peaks stored in the processor's memory. The incoming spectral signals are compared with the reference waveforms using a sliding correlation algorithm, which determines the control voltage required for adjusting the laser frequency to the desired lock point. The system has a scan amplitude of less than 1MHz when locked and it can re-lock for frequency drifts up to 10 GHz without human intervention. The dependence of laser frequency stability on ambient temperature, humidity, and pressure has been investigated. The performance of the system is suitable for experiments in atom trapping and atom interferometry that require long-term laser frequency stabilization. [Preview Abstract] |
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T1.00171: A Low-cost, Off-the-Shelf Ready Field Programmable Gate Array diode Laser Controller With adjustable parameters Ge Yang, John. F. Barry, Edward Shuman, David DeMille We have constructed a field programmable gate array (FPGA) based lock-in amplifier/PID servo controller for use in laser frequency locking and other applications. Our system is constructed from a commercial FPGA evaluation board with total cost less than {\$}400 and no additional electronic component is required. FPGA technology allows us to implement parallel real-time signal processing with great flexibility. Internal parameters such as the modulation frequency, phase delay, gains and filter time constants, etc. can be changed on the fly within a very wide dynamic range through an iPod-like interface. This system was used to lock a tunable diode laser to an external Fabry Perot cavity with piezo and current feedback. A loop bandwidth of 200 kHz was achieved, limited only by the slow ADCs available on the FPGA board. Further improvements in both hardware and software seem possible, and will be discussed. [Preview Abstract] |
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T1.00172: New technique for ``non-destructively" imaging cold alkali atom clouds Anand Ramanathan, Kevin Wright, Sergio Muniz, William Phillips, Gretchen Campbell, Kristian Helmerson In most cold atom experiments obtaining an image of the atomic cloud involves destroying the sample. Phase-contrast imaging can be used to get spatial density information with minimal perturbation of the sample, however, poor detection efficiency can greatly reduce the signal to noise ratio (S/N) obtained. We present a method which uses the ground state hyperfine structure and the $D_2$ cycling transition of alkali atoms to allow us to scatter many photons off each ``destroyed" atom, greatly compensating for optical detection losses. In our imaging technique, we transfer a small fraction (around 10\%) of the atoms from the $F=1$ hyperfine ground state to the $F=2$ ground state using a microwave or Raman pulse and then image those atoms with resonant probe light. The $F=2$ atoms leave the trap while the remaining $F=1$ atoms are not affected by the probe. The S/N is ultimately limited by statistical variation in the transfer fraction. This method works well even for optically thin atomic clouds. We use this partial transfer method to take multiple images of the same Bose-Einstein condensate. [Preview Abstract] |
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T1.00173: Spectroscopy with an unlocked frequency comb Bachana Lomsadze, Hyounguk Jang, Charles Fehrenbach, Eric Schultz, Brett DePaola In recent years, the use of frequency combs has greatly increased. They are used in atomic clocks and optical frequency metrology and synthesis. They are widely used in the spectroscopy of atomic and molecular systems as well. All experiments using frequency combs require high precision control on the two characteristic parameters of a frequency comb: repetition frequency (f$_{rep}$) and offset frequency (f$_0$); achieving this active control is often the most difficult aspect of frequency comb experiments. Here, we demonstrate high resolution spectroscopy using a frequency comb without the active stabilization of f$_{rep}$ and f$_0$. The underlying idea is that those frequencies can be measured {\it a posteriori} each time an excitation is observed. The natural tendency of f$_{rep}$ and f$_0$ to drift with time becomes equivalent to a controlled scan of those frequencies. [Preview Abstract] |
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T1.00174: Four-fold coincidence logic for photon counting with universal control David Branning, Sarthak Khanal, Young Ho Shin, Mark Beck Photon coincidence counting is a central technique in the field of quantum optics. We have built and tested a new coincidence-counting circuit that is faster, cheaper to assemble, and more portable than the commonly-used time-to-amplitude-conversion method. The circuit takes up to four TTL inputs (typically from avalanche photodiode photon-counting modules) and counts either 2-, 3-, or 4-fold coincidences between them within a user-selected coincidence time window as short as 10 ns. Up to eight user-defined coincidence combinations can be assigned to different TTL outputs, which may be monitored externally. Each of these outputs also increments a corresponding onboard 16-bit counter, whose value may be delivered to a computer over a USB interface at up to 400 Hz. Data acquisition is controlled via custom LabVIEW software. The circuit can accurately perform coincidence counting on Poisson-distributed inputs with mean rates of up to 24 MHz, with no dead-time effects. Because of its small size, low cost, and high bandwidth, this new circuit will find applications in quantum optics research at all levels, but it will be particularly beneficial to undergraduate teaching laboratories. [Preview Abstract] |
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T1.00175: Versatile single-chip event sequencer for atomic physics experiments Edward Eyler A very inexpensive dsPIC microcontroller with internal 32-bit counters is used to produce a flexible timing signal generator with up to 16 TTL-compatible digital outputs, with a time resolution and accuracy of 50 ns. This time resolution is easily sufficient for event sequencing in typical experiments involving cold atoms or laser spectroscopy. This single-chip device is capable of triggered operation and can also function as a sweeping delay generator. With one additional chip it can also concurrently produce accurately timed analog ramps, and another one-chip addition allows real-time control from an external computer. Compared to an FPGA-based digital pattern generator, this design is slower but simpler and more flexible, and it can be reprogrammed using ordinary `C' code without special knowledge. I will also describe the use of the same microcontroller with additional hardware to implement a digital lock-in amplifier and PID controller for laser locking, including a simple graphics-based control unit. This work is supported in part by the NSF. [Preview Abstract] |
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T1.00176: Integrating Sphere Alkali-Metal Vapor Cells Bart McGuyer, Amit Ben-Kish, Yuan-Yu Jau, William Happer An integrating sphere is an optical multi-pass cavity that uses diffuse reflection to increase the optical path length. Typically applied in photometry and radiometry, integrating spheres have previously been used to detect trace gases and to cool and trap alkali-metal atoms. Here, we investigate the potential for integrating spheres to enhance optical absorption in optically thin alkali-metal vapor cells. In particular, we consider the importance of dielectric effects due to a glass container for the alkali-metal vapor. Potential applications include miniature atomic clocks and magnetometers, where multi-passing could reduce the operating temperature and power consumption. [Preview Abstract] |
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T1.00177: Laser Ion Source Developments for Radioactive Ion Beams. Ruohong Li, Jens Lassen, Jean Philippe Lavoie, Andrea Teigelhoefer, Pierre Bricault, Jens Meissner The Resonant Ionization Laser Ion Source is a versatile and efficient tool to generate radioactive ion beams at on-line mass separator facilities. Due to its high ionization efficiency and elemental selectivity it allows to delivery, in principle, isobar free, clean radioactive ion beams (RIB). Parallel to the on-line laser ion source at TRIUMF's Isotope Separator and Accelerator facility, an off-line laser ion source test stand has been built for systematic laser resonance ionization spectroscopy and the development of ionization schemes. Three Ti:Sa lasers operating at 10 kHz repetition rate, with the option of harmonic frequency generation (doubling, tripling or quadrupling) are used to resonantly step-wise ionize the element of the interest. For systematic spectroscopic studies a grating tuned Ti:Sa laser is available that allows a continuous scan range up to 100 nm. With this laser inventory and the test stand Rydberg series and auto-ionizing levels can systematically be studied. Since August 2009 we have commissioned the system and studied Ga, Al and Ca with the new off-line system. The development of efficient laser resonant ionization schemes, their investigation and comparison using the laser ion source test stand and the all solid-state laser system will be discussed. [Preview Abstract] |
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T1.00178: THEORETICAL TECHNIQUES |
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T1.00179: Extracting momentum distributions from time-dependent wave functions J.H. Macek, S.Y. Ovchinnikov, J.B. Sternberg Time dependent state vectors for atomic processes are computed numerically and amplitudes for transitions to bound states obtained by projecting time-dependent state vectors onto bound state vectors at large times. Similar projections onto plane waves are used for continuum states. This requires large times since only then do plane waves represent particle motion. To use finite times, one projects onto asymptotic state vectors. Since the asymptotic states are often not known other procedures are sought. One such procedure replaces coordinates by the their classical counterpart, namely {\bf v}t, where {\bf v} is the velocity, and uses that coordinate space wave functions go over to momentum space wave functions at large times. This gives momentum distributions directly. In essence, if an exact wave function is obtained then there is no need to project that wave function onto imperfectly known asymptotic states to extract electron momentum distributions. We show how more familiar projection procedures derive from this simple prescription, which we call ``The Imaging Theorem" since it shows that momentum distributions image time-dependent wave functions. [Preview Abstract] |
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T1.00180: Computational method of molecular potentials from spectroscopic data Xuan Li, Cian Menzel-Jones, Moshe Shapiro We present a procedure that utilizes frequency-resolved fluorescence data from a reference potential to construct the corresponding potential energy surface and calculate its associated electronic transition dipole function. Our method is a fast and accessible alternative to an ab initio calculation with high accuracy. Compared to the RKR method, our procedure has the advantage to: (1) build a continuous potential above the dissociation limit, and (2) construct potentials with double minimums or local humps. In addition, we use the wavefunction of the calculated potential to construct the electronic transition dipole functions. We show the robustness of our procedure against insufficient or inaccurate fluorescence data through numerical simulations. Numerical simulations performed on both model systems and a diatomic Sodium molecule are presented. [Preview Abstract] |
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T1.00181: Residual Correlation Energies with Multi-Reference Density Functional Theory for Generalized Valence Bond Coupled-Cluster Methods Keith Lawler, Martin Head-Gordon We consider the extension of single reference Kohn-Sham theory to the case of a Generalized Valence Bond-Coupled Cluster (GVB-CC) wave function acting as a multi-configuration auxiliary wave function for Kohn-Sham theory. GVB-CC methods account for only strong (static) correlations. Density functional theory (DFT) can be combined with the GVB-CC method to account for the missing residual (dynamic) correlation energy that is typically missing from a multi-configurational wavefunction method. We specifically look at the combination of DFT with the perfect pairing (PP) and coupled cluster valence bond (CCVB) methods. We also explore methods for polarizing the densities utilized by DFT to obtain the appropriate dissociation limit when spin-restricted versions of the GVB-CC methods are used. [Preview Abstract] |
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T1.00182: Ro-vibrational energy spectra for three ions in an isotropic harmonic trap W. Blake Laing, Yujun Wang, B.D. Esry We study the three-body physics of bosonic ions in a spherical trap. In particular, we calculate the ro-vibrational energy spectra and the corresponding wavefunctions by solving the three-body Schr{\"o}dinger equation in the adiabatic hyperspherical representation. These calculations encompass ion trap frequencies and masses found in quantum information experiments and frequency standards studies. By analyzing the wavefunctions, we extract the geometry of these states and make a connection to the well-known Wigner crystal in plasma physics for both zero and non-zero total angular momentum. Finally, we will discuss the importance of quantum effects on the ions' ro-vibrational spectra. [Preview Abstract] |
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T1.00183: Hamiltonian Monodromy: Unexpected behavior of atoms in traps Chen Chen, John Delos, Megan Ivory, Seth Aubin A system exhibits monodromy if we take the system around a closed loop in its parameter space, and we find that the system does not come back to its original state. Hamiltonian dynamical monodromy occurs when an ensemble of trajectories forming a loop of initial conditions evolves continuously in time into a topologically different loop with the same total energy and angular momentum as the original ensemble. We will report a theoretical investigation of monodromy for atoms in optical traps. The calculations show how this phenomenon should become visible in experiments. [Preview Abstract] |
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T1.00184: ION COLLISIONS |
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T1.00185: Energy deposited to a carbon-60 molecule by a charged projectile Jim Perez, Krista Morris We have developed a computer simulation based on the Classical Trajectory Monte Carlo method to study the fragmentation of a carbon-60 molecule due to a charged projectile coming in close contact with it. The projectiles used range from protons to fully ionized argon, and the collision energies range from a few eV/amu to several hundred keV/amu. Along with our studies on fragmentation of the molecule we will report our results of calculations to investigate how energy is initially deposited to the molecule by the projectile and how that energy is re-distributed after the projectile has passed by. [Preview Abstract] |
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T1.00186: Theoretical Studies of Dissociative Recombination of Electrons with $\mathrm{N_2H}^+$ Ions D.O. Kashinski, R.F. Malenda, A.P. Hickman, D. Talbi, F. Gatti We are currently investigating the dissociative recombination (DR) of electrons with the molecular ion $\mathrm{N}_2\mathrm{H}^+$. The ion exists in the interstellar medium, and accurate DR rate constants are needed for astrophysical models. We are performing large scale electronic structure calculations of the excited-state potential surfaces of $\mathrm{N}_2\mathrm{H}$ necessary to treat the process $e^- + \mathrm{N}_2\mathrm{H}^+ \rightarrow \mathrm{N}_2 + \mathrm{H}$. The work is based on using the block diagonalization method to determine diabatic potential surfaces. The dissociating surface that governs DR is then is identified, and off-diagonal coupling terms can be used to determine the autoionization width $\Gamma$ that is essential for a dynamics calculation. The surface has been calculated for several different values of the NH distance and the NN--H bond angle. Dynamics calculations using the Multi-Configuration Time-Dependent Hartree (MCTDH) method are also underway. The status of these calculations will be presented at the conference. [Preview Abstract] |
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T1.00187: Angular distributions of collision induced dissociation: Dependence on kinetic energy release Kevin Carnes, Ben Berry, Wania Wolff, Nora G. Johnson, A. Max Sayler, Bishwanath Gaire, Mohammad Zohrabi, Jarlath McKenna, Itzik Ben-Itzhak Collisions between molecular-ion projectiles and atomic targets at energies of a few keV/amu lead predominantly to dissociative capture (DC) and collision-induced dissociation (CID). The CID process can be driven by electronic or vibrational excitation. The angular distribution of electronic CID, defined as the dissociation yield versus the angle between the molecular dissociation axis and the beam direction, is predicted by theory [Green and Peek, Phys. Rev. \textbf{183}, 166 (1969)] to depend on the internuclear distance R at the time of collision. That distance in turn can be related to the kinetic energy release of the dissociation. We examine this dependence for a range of molecular ions (H$_{2}^{+}$, HD$^{+}$, and HeD$^{+})$ and targets (He, Ne, and Ar) at collision energies of a few keV/amu. [Preview Abstract] |
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T1.00188: Ionization scaling law for high energy ion-aligned elliptic Rydberg hydrogen collisions Kevin Cornelius, Marc Ward, Thomas Cooper The classical trajectory Monte Carlo method was used to calculate electron ionization cross sections involving fully stripped ions of He, C, Ar and Kr colliding with an aligned elliptic Rydberg hydrogen atom for various excited n states. Cross sections from target eccentricities of -0.9 to 0.9 over the energy range 1.21 keV/u to 64 keV/u were used to develop a high energy ionization scaling law as a function of reduced collision speed, initial n state, projectile charge, and eccentricity. The proposed scaling law accurately predicts all theoretical CTMC cross section values for reduced collisions speeds larger than 2.5q. [Preview Abstract] |
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T1.00189: Single ionization of atomic hydrogen by proton impact as a three-body problem Alexander Godunov, Ana Samolov Recent measurements of Schulz et al for double differential cross section of single ionization in 75 keV proton-Hydrogen collisions provide a new insight into the three-body dynamic of ion-atom collisions. We have used two different theoretical methods to calculate differential cross sections in p+H ionization as a function of the scattering angle. The first method is based on approximate solution of Faddeev-Mercuriev equations for the three-body Coulomb problem. The second method is an expansion of the transition amplitude through the second order in the projectile-target interaction. These methods have been previously used to analyze direct ionization in proton- Helium collisions. The present calculations for differential cross sections as a function of the scattering angle are in reasonable agreement with experimental data of Schulz et al. The theoretical results not only reproduce the effect of three- body dynamics at small angles, and the role of heavy particle interactions at large angles, but demonstrate the right shape of the cross section at intermediate angles. [Preview Abstract] |
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T1.00190: Charge exchange in $C^{6+} + H$ and $C^{6+} + H_2$ collisions Nicolais Guevara-Leon, Bidhan Saha, John R. Sabin, Erik Deumens, N.Y. Ohrn In the solar wind, $C^{6+}$ ion is one of the most abundant ionic species and its interaction with comets as well as the atmosphere of planets of the solar system produces several interesting phenomena. The charge exchange reaction is one of the most relevant process as it may provide a possible explanation for the X-ray emission from these objects. Electron capture into a highly excited state of $C^{5+}$ ion usually generates radiation in the X-ray region of the spectrum. In the present work, charge exchange in $C^{6+} + H$ and $C^{6+} + H_{2}$ collisions are investigated theoretically using electron nuclear dynamics (END) [1] at projectile energies below the ionization threshold. For $H_2$ the one- and two- electron charge exchange cross sections are calculated and compared with other theoretical and experimental data. Orientation effects for the collision with the hydrogen molecules will also be discussed at the conference. [Preview Abstract] |
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T1.00191: State-Selective Single-Electron Capture by Ne$^{q+}$ (q = 3 -- 5) Ions from CO$_{2}$ Asad Hasan, Osama Abu-Haija, Asghar Kayani, Emanuel Kamber Energy-gain spectra and absolute total cross sections have been measured for single-electron capture processes in collisions of Ne$^{q+}$ recoil ions with CO$_{2}$ at laboratory impact energies between 25 and 300 qeV (q = 3 - 5, where q is the projectile charge state) and scattering angles between 0\r{ } and 5\r{ } using translational energy-gain spectroscopy technique. The energy-gain spectra show that only a few final states were selectively populated depending on the charge state of the projectile. In all collision systems studied here, the dominant reaction channels are due to non-dissociative single-electron capture into excited states of the projectile product. The final state populations will be discussed on the basis of the reaction windows, which are calculated using the single-crossing Landau-Zener model and the extended version of the classical over-the-barrier model. Further measurements of total cross sections for single-electron capture will also be presented and compared with theoretical calculations based on the multi-channel Landau-Zener (MCLZ) model. [Preview Abstract] |
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T1.00192: Electron capture by N$^{6+}$ in collisions with atomic hydrogen Y. Wu, P. Stancil, H. Liebermann, P. Funke, R. Buenker, Y. Hui, D. Schultz, I. Dragani, C. Havener Charge transfer due to collisions of ground state N$^{6+}$($1s~^2S$) with atomic hydrogen has been investigated using a variety of theoretical and experimental approaches. Total, $n$-, $\ell$-, and $S$-resolved cross sections are obtained and compared to the limited available data for collision energies between 10 meV/u and 25 keV/u. The quantum-mechanical molecular-orbital close-coupling (QMOCC), classical trajectory Monte Carlo, atomic-orbital close-coupling, and multichannel Landau-Zener methods are applied in order to cover the large range of considered collision energies. The QMOCC calculations utilized adiabatic potential and nonadiabatic couplings obtained with the multi-reference single- and double-excitation configuration interaction approach. In particular, we focus on the triplet-singlet cross section ratios as they have the potential to influence x-ray emission predictions for heliospheric and Martian exosphere spectra due to $\sim$1 keV/u solar wind ion collisions. The absolute total cross sections are constrained by ion-atom merged-beams measurements. [Preview Abstract] |
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T1.00193: Collisional excitation and emission of H$_{\alpha}$ Stark multiplet in fusion plasmas Yu. Ralchenko, O. Marchuk, R.K. Janev, W. Biel, E. Delabie, A.M. Urnov We study the excitation of parabolic Stark states in hydrogen atoms by collisions with fast ions. It is shown that excitation cross sections are very sensitive to the angle between the electric field and the projectile velocity. The calculated collisional data are implemented in a newly developed collisional-radiative model involving parabolic quantum states of hydrogen. Our simulations are shown to explain the frequently observed non-statistical behavior of the H$_{\alpha}$ component intensities under typical conditions of a motional Stark effect (MSE). A good agreement with the MSE data from the Joint European Torus (JET) for emission of the $\sigma$ and $\pi$ components (Mandl et al 1993 Plasma Phys. Control Fusion 35 1373) is obtained for the first time. [Preview Abstract] |
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T1.00194: Electron capture cross section for Li$^+$ on H and H$_2$: Experiment and theory C. Cisneros, I. Alvarez, R. Cabrera-Trujillo, A. Guerrero We present a theoretical and experimental study of the electron capture cross section for Li$^+$ in the range from 0.1 to 25 keV/amu colliding on atomic and molecular hydrogen. We report the total and differential in the angle cross section for the channel Li$^+\to$ Li and compare with available experimental and theoretical data found in the literature. The theoretical study is based on the application of a non-adiabatic electron-nuclear dynamics approach. [Preview Abstract] |
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T1.00195: Bound states, resonances, and formation of the H$_3^-$ anion Viatcheslav Kokoouline, Mehdi Ayouz, Jacques Robert, Olivier Dulieu Accurate potential energy surface and permanent dipole moments of the H$_3^-$ molecule are calculated. The obtained potential energy surface is used to obtain bound states, rotational constants, predissociated vibrational resonances and their lifetimes of the four isotopologues, H$_3^-$, H$_2$D$^-$, D$_2$H$^-$, and D$_3^-$, of the ion. We have also calculated the cross-section for the formation of H$_3^-$ by radiative association: H$_2+$H$^-\to$H$_3^- +\hbar\omega$. The obtained results suggest that the H$_3^-$ ions can be formed in the interstellar medium (ISM). An eventual detection of H$_3^-$ in the ISM would also be a proof that the H$^-$ ion is present in the ISM. [Preview Abstract] |
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T1.00196: Nuclear Spin Effects in the Reactions of H$_3^+$ with H$_2$ and Electrons Holger Kreckel, Kyle Crabtree, Carrie Kauffman, Brian Tom, Oldrich Novotny, Max Berg, Dennis Bing, Henrik Buhr, Claude Krantz, Michael Lestinsky, Mario Mendes, Christian Nordhorn, Julia Stutzel, Andreas Wolf, Richard Thomas, Benjamin McCall H$_3^+$ is the simplest polyatomic molecule. It is widely used as a benchmark for theoretical calculations of molecular spectroscopy and reaction dynamics, and also plays a pivotal role as the cornerstone of interstellar chemistry. In Urbana, we have investigated the proton hop/exchange reaction H$_3^+$ + H$_2$ $\rightarrow$ (H$_5^+$)$^*$ $\rightarrow$ H$_2$ + H$_3^+$ for the first time at low temperatures. This reaction is the simplest bimolecular reaction involving a polyatomic, and is also the most common bimolecular reaction in the universe. Our experiments have revealed the branching ratio between proton hop and exchange, and appear to explain the observed {\em ortho:para} ratio of H$_3^+$ in diffuse interstellar clouds. At the TSR storage ring of the Max Planck Institute for Nuclear Physics in Heidelberg, we have performed high-resolution measurements of the dissociative recombination (DR) cross sections of cold H$_3^+$ in different mixtures of its lowest {\em ortho} and {\em para} quantum states. These measurements represent an important step towards the first state-selected DR measurements. [Preview Abstract] |
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T1.00197: Preliminary results on a new method for producing ultracold molecular ions Wade Rellergert, Scott Sullivan, Kuang Chen, Julia Clark, Steven Schowalter, Eric Hudson We describe a new method for the production of ultracold molecular ions. This method utilizes sympathetic cooling due to the strong collisions between appropriately chosen molecular ions and laser-cooled neutral atoms to realize ultracold, internal ground-state molecular ions. In contrast to other experiments producing cold molecular ions, our proposed method efficiently cools both the internal and external molecular ion degrees of freedom. The availability of truly ultracold molecular ions will impact fields as diverse as quantum chemistry, precision measurement, and quantum information/computation. Results from BaCl$^+$ trapping experiments, as well as work aimed at cooling trapped BaCl$^+$ ions using ultracold Ca atoms are presented. [Preview Abstract] |
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T1.00198: Improved Ionization Equilibrium Calculations for Optically Thin Plasmas Daniel Wolf Savin, Paul Bryans, Nigel R. Badnell, Thomas W. Gorczyca, J. Martin Laming, Warit Mitthumsiri Reliably interpreting spectra from electron-ionized laboratory and cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and their reliability are often highly suspect. We have carried out state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Na-like ions of all elements from He to Zn as well as for Al-like to Ar-like ions of Fe. We have also carried out state-of-the-art radiative recombination (RR) rate coefficient calculations for the bare through Na-like ions of all elements from H to Zn. Using our data and the recommended electron impact ionization data of Dere (2007), we present improved collisional ionization equilibrium calculations. We compare our calculated fractional ionic abundances using these data with those presented by Mazzotta et al. (1998) for all elements from H to Ni. [Preview Abstract] |
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T1.00199: Slow Collisions of Si3+ with Atomic Hydrogen D.C. Joseph, J.-P. Gu, B.C. Saha, H.P. Liebermann, P. Funke, R.J. Buenker Low energy electron capture from hydrogen atom by multi-charged ions continues to be of interest and applications include both magnetically confined fusion and astrophysical plasmas. The charge exchange process reported here\textit{, Si}$^{3+} + H$ $\rightarrow $ \textit{Si}$^{2+} + H^{+}$ is an important destruction mechanism of Si$^{3+}$ in photo-ionized gas. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si$^{3+}$, with neutrals in the cometary gas vapor. The state selective cross sections are evaluated using the full quantum [1] and semi-classical molecular orbital close coupling (MOCC) [2] methods. Adiabatic potentials and wave functions for a number of low-lying singlet and triplet states of and symmetry are calculated wing the MRD-CI package [3]. Details will be presented at the conference. \\[4pt] [1] L. B. Zhao, D. C. Joseph, B. C. Saha, H. P. Liebermann, P. Funke and R. J. Buenker, Phys. Rev A, \textbf{79}, 034701 (1009).\\[0pt] [2] M. Kimura and N. F. Lane, At. Mol. Opt. Phys \textbf{26}, 79 (1990).\\[0pt] [3] R. J. Buenker, ``Current Aspects of Quantum Chemistry 1981, Vol \textbf{21}, edited by R. Carbo (Elsevier, Amsterdam) p 17. [Preview Abstract] |
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T1.00200: Construction of a Unique Laboratory Instrument to Study the Cosmic Origins of Organic Chemistry Kenneth A. Miller, Daniel Wolf Savin The cosmic pathway towards life is thought to begin in molecular clouds when atomic carbon is ``fixed'' into molecules, initiating organic chemistry and the synthesis of complex organic species. Much of our knowledge of this process is through spectroscopic observations and sophisticated astrochemical models to interpret the collected spectra. However, our understanding of the molecular universe is limited by uncertainties in the underlying chemical data in these models. Of particular importance are data for reactions of neutral atomic carbon with molecular ions. To study these chemical reactions we are building a unique instrument which will not suffer from the limitations of previous experimental methods. Starting with a C$^{-}$ beam, we will use laser photodetachment to generate a C beam. Then the C$^{-}$ will be removed electrostatically leaving a pure C beam. A molecular ion beam will be merged with the C beam. Since the beams will be co-propagating, we will be able to study reactions down to collision energies of a couple tens of meV ($\sim $140 K) and possibly lower. Reactions will be studied using an energy analyzer to separate and detect the charged end products, allowing us to determine absolute reaction cross sections. [Preview Abstract] |
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T1.00201: POST-DEADLINE ABSTRACTS III |
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T1.00202: Observation of electromagnetically induced transparency and electromagnetically induced absorption in warm Rb vapor using a single linearly polarized laser Samir Bali, Peter Harnish, Eric Williams We have observed electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) in room temperature Rubidium. EIA was observed on $F_{g} = 3 \rightarrow F'$ transitions in ${}^{85}$Rb and on $F_{g} = 2 \rightarrow F'$ transitions in ${}^{87}$ Rb. EIT was observed on $F_{g} = 2 \rightarrow F'$ transitions in ${}^{85}$Rb and, for the first time, on $F_{g} = 1 \rightarrow F'$ transitions in ${}^{87}$ Rb. Good signal-to-noise was obtained by using a single linearly polarized laser and a magnetic field collinear with the laser beam passing through the atomic sample. We discuss the dependence of the EIT and EIA signals on the polarization direction of the incident laser beam. [Preview Abstract] |
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T1.00203: A Correction to QED at Boundaries Richard Kriske The author would like to point out a minor correction to QED at spherical boundaries, that may be of some use in Cosmology and interestingly enough in QCD calculations. It seems that at boundaries that are not fixed, but rely on relative positioning of the observer and the boundary (when the boundary moves with the observer on a long road for instance when the driver looks down a road and sees a mirage of water in the road and the mirage moves with the observer) the many paths summation principle in QCD can be corrected. [Preview Abstract] |
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T1.00204: Decomposition and Schematic Construction of Higher-Dimensional Unitary Transformations Blane McCracken, Tae-Woo Lee, Changjun Min, Jonathan Dowling The unitary properties inherent in linear optical components have a wide variety of applications in quantum sciences including imaging, sensing, and quantum computing. Although the complex unitary operations required by many of these sophisticated applications span a large Hilbert space, it has been shown that these operators can be decomposed into a product of multiple two-dimensional subspace transformations. This discovery enables the practical design of any arbitrary unitary transformation proposed in theory. Furthermore, numerical optimization has recently been utilized for generating maximally efficient quantum states and subsequent unitary transformations specific to particular applications. We propose a numerical method of decomposing and schematically constructing the 2-dimensional subspace components required for experimental implementation of any arbitrary unitary operator. Specifically, we demonstrate a practical design to previously discovered, numerically optimized, unitary transformations. Finally, we implement algorithms for minimizing optical components necessary for experimental realization. [Preview Abstract] |
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T1.00205: Dissipative Transport of a Bose-Einstein Condensate with Tunable Interactions D. Dries, S.E. Pollack, J. Hitchcock, R.G. Hulet We study the superfluid nature of a BEC in an optical dipole trap combined with either a disordered potential or a single Gaussian defect. Through measurement of the damping of the collective dipole mode, we characterize the velocity dependence of the dissipative transport, as well as its dependence on disorder or defect strength. For both a disorder potential and a single Gaussian defect, we observe weak or no damping for a BEC velocity $v\gg c$, maximum damping for $v\sim c$ and weak damping for $v\ll c$ where $c$ is the speed of sound in the BEC. For the case of a single defect, we observe a critical velocity for damping that depends on defect strength. \textit{In situ} images of quasi-1D BECs provide evidence that the damping is driven, in part, by dark soliton formation. Time-of-flight images of condensates in the 3D regime also provide evidence of dark soliton formation. In this regime strong damping is observed, even for weak disorder or defect strength. We also investigate the nature of the damping for different values of the $s$-wave scattering length $a$ with $0.1\,a_0 [Preview Abstract] |
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T1.00206: Using Rydberg atoms to the control electron temperature in an ultra-cold plasma Duncan Tate, Lauren Rand, Cristian Vesa, Roy Wilson, Thomas Gallagher In this presentation, we will describe recent results of experiments in which Rydberg atoms are embedded into an ultra-cold plasma. The plasma is created by partial photoionization of a dense, cold sample of rubidium atoms in a MOT using a Littman dye laser. After ionization, the ions have the same temperature as the parent atoms, while the initial electron temperature, $T_e$, depends on the Littman laser photon energy. At a controllable time delay (20 ns - 10 $\mu$s), neutral atoms embedded in the plasma are excited to a specific Rydberg state by a narrow bandwidth pulsed laser. In such a system, it is predicted that the plasma electrons may be cooled if the Rydberg binding energy, $E_b$, is greater than $4k_BT_e$. Our preliminary results indicate that the evaporation rate of electrons from a plasma with $T_e = 50$ K is suppressed by the addition of $36d$ Rb atoms ($E_b = 2.6 \ k_B T_e$). In addition, we find that recombination of ions and electrons into high-$n$ Rydberg states is enhanced by addition of $36d$ atoms (indicating a lower $T_e$, since $\Gamma_{TBR} \propto T_e^{-9/2}$). On the other hand, recombination is suppressed by the addition of $26d$ atoms ($E_b = 5.2 \ k_BT_e$) to the plasma, suggesting an increase in the electron temperature. [Preview Abstract] |
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T1.00207: Ultracold rubidium-87 atoms in a stabilized QUEST Dwight Whitaker, Arolyn Conwill, Eric Stutz We have created a closed-loop servo system to stabilize the power to a CO$_2$ laser used to trap and cool at cloud of $^{87}$Rb atoms. We will discuss the effects of power stabilization on temperature reproducibility as well as the behavior of trapped atoms in an ultra-stable trap. This system is designed to create a cloud of atoms with a temperature that is well characterized and highly reproducible. Such a trap could be useful for studying finite temperature dependence of the BEC phase transition as well as experiments on BECs at finite temperature. [Preview Abstract] |
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T1.00208: Optical bistability in cold atom cavity systems Prasanna Venkatesh Balasubramanian, Duncan O'Dell, Jonas Larson Coupled cold atom-cavity/BEC-cavity systems have attracted significant attention owing to their appeal as optomechanical systems [1] and as probes of atomic many body quantum effects in a novel setting [2]. We investigate the non-linear nature of the effective Hamiltonian that describes the cavity-atom system. We analyse the energy dispersion derived from the effective Hamiltonian in regions where the atom-cavity system exhibits bistability. \\[4pt] [1] F. Brennecke et.al., Science \textbf{322}, 235 (2008)\\[0pt] [2] J.Larson et.al., Phys. Rev. Lett. \textbf{100}, 050401 (2008) [Preview Abstract] |
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T1.00209: Adiabatic Preparation of Many-Body States in Optical Lattices Michael Gullans, Mark Rudner, Anders S{\O}rensen, Ehud Altman, J.V. Porto, Eugene Demler, Mikhail Lukin We analyze a technique for the preparation of low entropy many body states of atoms in optical lattices based on adiabatic passage. In particular, we show that this method allows preparation of strongly correlated states as stable highest energy states of Hamiltonians that have trivial ground states. As an example, we analyze the generation of antiferromagnetically ordered states by adiabatic change of a staggered field acting on the spins of bosonic atoms with ferromagnetic interactions. [Preview Abstract] |
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T1.00210: On the Synthesis and characterization of Rhodamine 6G doped ZnO Nanorod Arrays for Solar cell Fozia Z. Haque, Lokesh Shastri, Krishna S. Pandey, Mushahid Husain Dye sensitized solar cell (DSSC) using ZnO nanoparticles provides a technically and economically credible alternative concept to present day p-n junction photovoltic device. The conventional systems where the semiconductors assume both the task of light absorption and charge carrier transport the two junctions are seprated here. In DSSC the light is absorbed by a sensitizer. In our investigation the DSSC consist of Zno nanoparticles that have a large surface area are used to harvest sunlight. Firstly the ZnO nanoparticals were grown on FTO substrate and then this nanoparticals were used as seed layers to grow aligned nanorods and used them as the wide band gap semiconductor electrod for solar cell. ZnO electrodes were sensitized by Rhodamine 6G dye. ZnO nanoparticles and nanorods were observed through SEM and their crystallinity were investigated using XRD. The higher efficiency in DSSC is possible due to the increased surface area from the nanoparticles facilitating the fast electron transport through the nanowires. [Preview Abstract] |
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T1.00211: Observation of pseudogap phase is a strongly interacting Fermi gas John Gaebler, J.T. Stewart, T.E. Drake, D.S. Jin, A. Perali, P. Pieri, G.C. Strinati We demonstrate that a pseudogap phase exists above the superfluid phase transition in an atomic Fermi gas. To observe this pseudogap phase we make two independent measurements. First, we make a direct measurement of the superfluid phase transition temperature by probing pair condensation in momentum space. Second, we probe the single-particle spectral function using an analog to photoemission spectroscopy which gives us the density of states and the dispersion E(k). In our measurements, we observe no qualitative change in the single-particle spectral function even as the temperature of the Fermi gas is increased from below to above the superfluid transition temperature. This is the first model-independent evidence for a pseudogap in atomic Fermi gases. [Preview Abstract] |
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T1.00212: Measurement of the trap parameters of a magneto-optical trap by optically driving laser intensity Geol Moon, Myoung-Sun Heo, Yonghee Kim, Jihyoun Kim, Heung-Ryoul Noh, Wonho Jhe We report a simple method for trap parameter measurement by realizing forced harmonic oscillation in a magneto-optical trap (MOT). Through the resonance curve of the vibrational amplitude of the harmonic oscillation on the driving frequency of the laser intensity, we measured the damping coefficient and trap frequency of trapped atoms in the MOT under various conditions and compared them with those obtained from the parametric resonance. In particular, we report a significant effect of a transverse laser on one-dimensional harmonic oscillation. This effect is expected to explain the discrepancies in other previous experiments between the experimental and theoretical results. [Preview Abstract] |
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T1.00213: Universality in Three- and Four-Body Bound States of Ultracold Atoms S.E. Pollack, D. Dries, R.G. Hulet The universal regime of Efimov few-body physics occurs when the strength of the interparticle interaction is much larger than the effective range of the two-body potential. By exploiting a broad Feshbach resonance in the $|1,1\rangle$ hyperfine state of $^7$Li, we can tune the interactions well into the universal regime. The rate of atom loss from our optical trap increases by 9 orders of magnitude from the weakly interacting regime to the strongly interacting regime, allowing unprecedented access to universal physics. We find evidence for two universally connected Efimov trimers in addition to their associated four-body bound states. Intimately related to the Efimov trimers, two tetramer states exist for each trimer, and no additional parameters are required to describe their binding energies. A total of eleven features in the three- and four-body inelastic loss spectra are discovered. The relative locations of these features on either side of the Feshbach resonance agree with universal theory, whereas a systematic deviation from universality is found when comparing features across the resonance. Pollack, {\it et al.}, Science {\bf 326}, 1683 (2009). [Preview Abstract] |
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T1.00214: Verification of Universal Relations in a Strongly Interacting Fermi Gas Tara Drake, John Gaebler, Jayson Stewart, Deborah Jin Many-body fermion systems are important in many branches of physics, including condensed matter, nuclear, and now cold atom physics. In many cases, the interactions between fermions can be approximated by a contact interaction. A recent theoretical advance in the study of these systems is the derivation of a number of exact universal relations that are predicted to be valid for all interaction strengths, temperatures, and spin compositions. These equations, referred to as the Tan relations, relate a microscopic quantity, the amplitude of the high-momentum tail of the fermion momentum distribution, to the macroscopic thermodynamics of the many-body system. Our experiments aim to verify the Tan relations in a strongly interacting gas of fermionic atoms. Specifically, we measure the fermion momentum distribution using two different techniques, along with the rf excitation spectrum, and determine the effect of interactions on these microscopic probes. We then measure the potential energy and release energy of the trapped gas and test the predicted universal relations. [Preview Abstract] |
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T1.00215: Dark Energy Drives Vibrating Atoms, Chain reactions, Etc.: Charles Sven The 14 billion year old atom - destroyed Hiroshima, vibrates at a 100 trillion times/sec, emanates photons at the speed of light, contains atom sized proton force field that attracts electrons, all driven by ``Dark Energy.'' This ageless atom's superpowerful requirements, must be supplied from a huge, external, super high-frequency, super-cooled, ``Dark Energy field,'' undetected by current technology, existing for 14+ billion years without degradation. Demonstrating this age-old atom's ``dark energy'' power source requires the synthesis of a number of elements, forces, observations and experiments, many of which are combined in novel but only in replicable venues. Solution includes ``Dark Energy'' participation in celestial observations. Expanded excerpt from my presentation at: the American Physical Society's April meeting in Denver 2009 Section T8: Cosmology [Preview Abstract] |
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T1.00216: Dynamic Order-Reversal Transition in a Parametrically Driven Cold Atomic System Ji-Hyoun Kim, Yonghee Kim, Geol Moon, Myoung-Sun Heo, Wonho Jhe We experimentally demonstrate the reversal transition of the order in a parametrically driven cold atomic system which shows ideal mean-field symmetry-breaking transition, by the application of the pulsed additional bias-field opposite to the pre-existing order. The strength $h_{0}$ and the duration \textit{$\Delta $t} of pulse are the control parameters of the reversal transition. We obtain the phase boundary of the transition and there is critical slowing down behavior near the phase boundary via diverging relaxation time. [Preview Abstract] |
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T1.00217: Effects of laser linewidth on the back-action cooling of optomechanical resonators Gregory A. Phelps, Daniel S. Goldbaum, Pierre Meystre The effects of laser linewidth on the final temperature of a dynamical back-action cooled mirror in a Fabry-P\'{e}rot resonator coupled to an external phonon bath are examined. Classical Monte-Carlo techniques are used to model the colored laser noise with correlation function $<\phi $(t) $\phi $(t')$>$=exp(-$\vert $t-t'$\vert $/$\tau )$ and mean $<\phi $(t)$>$=0. We present results of an analytical and numerical analysis that quantifies the final temperature of the mirror as a function of laser linewidth for experimentally realizable parameters. [Preview Abstract] |
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T1.00218: Microscopic Treatment in Nucleation Karla Galdamez In nucleation, position dependent mass (PDM) Hamiltonian has not been analyzed because of the potentially foundational questions it raises. Further, the quantum effects exhibited in this system have been well established. Thus, nucleation provides an interesting template to investigate quantum effects exhibited in macroscopic systems. We will approach our problem from two different perspectives. First, starting from first principles (ab initio), we will present a microscopic description of nucleation arriving at a final quantum mechanical Hamiltonian. Subsequently, we will introduce the topic of rules of quantization with an emphasis on the Weyl transform. Surprisingly, our ab initio microscopic treatment is equivalent to that of Weyl quantization thus revealing a 1:1 correspondence between quantum and classical representation methods. [Preview Abstract] |
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