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 E1: Poster Session I (4:00 pm - 6:00 pm) |
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Room: Exhibit Hall |
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E1.00001: MATTER WAVE INTERFEROMETRY AND ATOM OPTICS |
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E1.00002: Simulations of a multi-level atom interferometer B. Barrett, I. Chan, C. Mok, A. Carew, R. Berthiaume, A. Kumarakrishnan, I. Yavin We present numerical simulations to understand a multi-level atom interferometer used for precision measurements with laser cooled atoms. In the experiment, a standing wave pulse (swp) is applied at $t = 0$ which creates a superposition of momentum states. At $t = T$, a second swp diffracts the momentum states again so that a density grating is formed in the vicinity of $t = 2T$. This grating is associated with the interference of $p$-states differing by multiples of the 2-photon recoil momentum ($n \hbar q = 2 n \hbar k$). A traveling wave readout pulse Bragg scatters light only from the grating with spatial periodicity $\lambda/2$ (associated with interfering $p$-states differing by $\hbar q$). Coherent backscatter due to the readout pulse is detected as the signal. A model of the experiment is realized by numerically solving the Schr\"{o}dinger equation for a multi-level atomic wave packet subject to a time-dependent standing wave potential. The simulation models several aspects of the experiment, such as the dependence of the signal on pulse duration, intensity and detuning. It is also used to explain the effect of spontaneous emission and magnetic sub-level populations on the experiment. A comparison of the simulations to experimental data is presented. [Preview Abstract] |
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E1.00003: Progress Towards a High Precision Atom Interferometric Measurement of Gravitational Acceleration Carson Mok, Robert Berthiaume, Scott Beattie, Brynle Barrett, Iain Chan, A. Kumarakrishnan We have developed an echo type ground state atom interferometer to measure gravitational acceleration, $g$. The interferometer uses two standing wave pulses at $t=0,$ and $t=T$ to diffract and interfere momentum states of $^{85}$Rb atoms separated by $2 \hbar k$ in the vicinity of the echo time $t=2T$. Matter wave interference at this time results in the formation of a density grating. The positional phase from this grating is measured by coherently backscattering light from the laser cooled sample. The phase of the backscattered light that is measured with respect to an optical local oscillator, scales as $gT^{2}$. We review improvements with respect to previous work (PRA \textbf{73} 063624 (2006)) that are associated with better passive isolation, phase initialization at the beginning of the experiment, and stabilization of the optical phase drifts during the measurement using RF techniques. [Preview Abstract] |
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E1.00004: Realization of An Inexpensive Multi-Channel Frequency Synthesizer Adam Carew, R. Berthiaume, C. Mok, I. Chan, B. Barrett, M. Weel, A. Kumarakrishnan We present a high-precision RF synthesizer that uses phase locked loops for deriving multiple outputs for applications in atomic physics such as optical lattices and atom interferometry. The synthesizer utilizes inexpensive, readily-available components to produce dual RF outputs that are tunable over $\sim50$ MHz in the vicinity of 250MHz. The difference frequency between the outputs can be tuned from $\sim10$ mHz to 50 MHz. We achieve exceptional frequency stability by using a rubidium reference at 10 MHz. The RF outputs are also phase stabilized using a feedback loop so that the phase remains constant as the frequency is changed. [Preview Abstract] |
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E1.00005: ABSTRACT WITHDRAWN |
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E1.00006: Molecular interferometry with $^2\Sigma$ molecules in large magnetic fields Sergey Alyabyshev, Roman Krems $^2\Sigma$ molecules in superimposed magnetic and electric (static or laser) fields exhibit avoided crossings between Zeeman levels of different rotational states as functions of external field parameters [1]. We explore the possibility of using these avoided crossings for molecular interferometry experiments. Our calculations demonstrate that the population of a particular spin state is extremely sensitive to both electric and magnetic fields near avoided crossings between Zeeman levels corresponding to the rotationally ground N=0 and rotationally excited N=1 states. The position and strength of these avoided crossing can be tuned by varying the external fields [1,2]. We propose that an interferometry experiment using $^2\Sigma$ molecules in the presence of a microwave laser field can be used to probe small fluctuations of the magnitude ($\sim$1 Gauss on the background of 4 Tesla) and direction of large magnetic fields (2 - 6 Tesla) on the molecular length scale. \\[4pt] [1] T.V. Tscherbul and R.V. Krems. Physical Review Letters 97, 083201 (2006)\\[0pt] [2] S.V. Alyabyshev and R.V. Krems, Physical Review A 80, 033419 (2009) [Preview Abstract] |
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E1.00007: Interactions of Bright Matter-Wave Solitons with a Barrier Potential E.J. Olson, S.E. Pollack, D. Dries, R.G. Hulet Nondispersive solitary waves (solitons) can be produced in a one-dimensional Bose-Einstein condensate (BEC) with weak attractive interactions. We have created bright matter-wave solitons with $N\sim2\times10^5$ ultracold $^7$Li atoms by tuning the scattering length to small negative values via the broad $|1,1\rangle$ Feshbach resonance. In this work, we study the interaction between a kicked soliton and a thin barrier potential generated by a near-resonant cylindrically focused laser beam. Our results show that by varying the soliton kinetic energy, as well as the potential strength, it is possible to reflect, transmit, or even split the soliton. We investigate the possibilities for creating a matter-wave beamsplitter and a matter-wave interferometer by examining the recombination of the solitons. Theory has shown that in certain cases the solitons behave as single quantum mechanical objects that may split into a Schr\"{o}dinger cat state. [Preview Abstract] |
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E1.00008: Atom Interferometry Experiments in Fundamental Physics PeiChen Kuan, Shau-Yu Lan, Brian Estey, Cheong Chan, Holger Mueller Light-pulse atom interferometers have already been used to measure gravity, the fine structure constant, gravity gradients, and Newtons gravitational constant with high precision and accuracy. Recent developments like large-momentum transfer (LMT) beam splitters for matter waves, e.g. using a combination of Bloch oscillations and Bragg diffraction, increase the space-time area enclosed between the interferometer arms. This promises to boost the sensitivity of atom interferometer by several orders of magnitude. Furthermore, the common mode noise of interferometers can be removed by running a pair of conjugated interferometers simultaneously. Here, we report our recent progress of atom interferometer experiments. [Preview Abstract] |
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E1.00009: Test of the equivalence principle using Li atom interferometry Geena Kim, Holger Mueller Atom interferometry has been a versatile tool for precision measurement on various fundamental constants and testing fundamental physics. Our long term goal is to test the Einstein equivalence principle (EEP) using atom interferometry with Lithium and Cesium atoms. The dissimilarity of these species will enhance the influence of certain violations of the EEP in our experiment, compared to similar experiments that use rubidium isotopes. For example, Lithium atoms are very special in the sense that their nuclear binding energy per nucleon is much lower than the one of most other atoms. To achieve high sensitivity of the atom interferometer we plan to use large momentum transfer technique by using Bloch-Bragg-Bloch beam splitters(which utilize Bloch oscillations and Bragg diffraction) incorporated in Ramsey-Borde interferometer [1,2]. Our recent progress on building lithium atom interferometry will be presented.\\[4pt] [1] H. Mueller et al., Atom Interferometry with up to 24-Photon-Momentum-Transfer Beam Splitters, Phys. Rev. Lett. 100, 180405 (2008).\\[0pt] [2] H. Mueller et al., Atom Interferometers with Scalable Enclosed Area,Phys. Rev. Lett. 102, 240403 (2009). [Preview Abstract] |
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E1.00010: Precision Atom Interferometry with Bose-Einstein Condensates Alan Jamison, Vladyslav Ivanov, Nathan Kutz, Subhadeep Gupta Interferometry using laser cooled atom sources diffracted by standing waves of light can achieve remarkable sensitivity in diverse measurements such as that of local gravity, gravity gradients, and atomic photon recoil. A key feature of these achievements is the narrow velocity distribution of laser cooled atom sources. While a Bose-Einstein condensate (BEC) source provides an even narrower velocity distribution, the higher atomic interaction energy (mean field) introduces a new systematic error to the measurement. Using a contrast atom interferometry technique with sodium Bose-Einstein condensates (BEC), atomic photon recoil was measured [1] to 7 parts per million (ppm) precision but 200 ppm accuracy, limited by the mean field systematic. We analyze the complete effect of the mean field interaction by numerically simulating the experiment using the nonlinear Gross-Pitaevskii equation. Together with this analysis we will also present our plans to extend the experimental technique to ytterbium BECs to achieve part-per-billion (ppb) level sensitivity. A measurement of the photon recoil at this level will provide a new competitive measurement of the fine structure constant $\alpha$ at the sub-ppb level. [1] S. Gupta et al, Phys Rev Lett 89, 140401 (2002) [Preview Abstract] |
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E1.00011: Study of the effect of dynamics of cold atoms in a magnetic guide on de Broglie wave interferometer Alexey Tonyushkin, Mara Prentiss We present experimental study of dynamics of cold thermal atoms loaded into macroscopic magnetic guides [1] and its impact on the coherence of a de Broglie wave interferometer. Previous studies showed that cold atoms loaded into ferromagnetic guides exhibit oscillatory dynamics, which can be explained by the classical caustics formed by trajectories of individual atoms [2]. Such oscillatory patterns depend on the loading sequence, the atom's temperature, and the final field gradient. We show that caustics may limit the coherence time of the atom interferometer. In addition, the caustics may make it harder to achieve the quantum freeze limit, where slight misalignment of optical beams does not adversely affect the interaction time. In conclusion, the suppression of caustics in guided atom interferometers is important for increasing the sensitivity of atom-interferometer-based inertial sensors.\\[4pt] [1] A. Tonyushkin and M. Prentiss, submitted (2009), arXiv:0908.3504\\[0pt] [2] W. Rooijakkers {\em et al.}, PRA {\bf 68}, 063412 (2003). [Preview Abstract] |
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E1.00012: Ion Interferometry Christopher J. Erickson, Mary Lyon, Aaron Bennett, Daylin Troxel, Kelvin J. Blaser, Stuart Harper, Dallin S. Durfee We report on the progress of an ion interferometer based on a laser-cooled $^{87}$Sr$^+$ beam which will be split and recombined using stimulated Raman transitions. This device will be used to implement an extremely precise electromagnetic field sensor. Design considerations and instrumentation development will be discussed. Possible practical and fundamental applications, including deviations from Coulomb's inverse-square law and the search for a possible photon rest mass, will be discussed. [Preview Abstract] |
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E1.00013: Further Toward a Li-Rb Ring Interferometer Ryan Olf, G. Edward Marti, Anton \"Ottl, Dan Stamper-Kurn We report on the design and current status of our experimental approach to create non-trivial, multiply connected trap geometries for quantum gases and atom interferometry. Our novel setup consists of a second-generation magnetic ring trap that employs micro-fabricated magnetic coils with 3D integration housed in a low magnetic field noise environment. These coils generate very precise, smooth and tightly confining trapping fields. The diameter of the magnetic ring trap can be controlled and adjusted over a wide range, from tens of microns to several millimeters. Thus, the apparatus can provide increased sensitivity when operated as a Sagnac-type interferometer (large ring), while still allowing us to fill the ring with degenerate quantum gases and study the effects of non-trivial topology on coherence and dynamics of Bose-Einstein condensates (small ring). Further, optical access permits us to tailor the trapping potential with precisely controlled optical fields, for example, to create tunneling barriers or beam splitters. We load the ring trap with both rubidium and lithium atoms, which will allow us to explore diverse regimes of matter-wave interferometry with bosonic and fermionic atoms of differing interaction strengths, including attractive and repulsive condensates. [Preview Abstract] |
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E1.00014: Multi-species atom interferometry Catherine Klauss, Ivan Hromada, William Holmgren, Vincent Lonij, Alex Cronin Our nanograting atom interferometer now works with Na, K, and Rb atom beams. We also have studied diffraction of Li, Sr, and He* in the same apparatus. Comparing results from several atomic species provides new scientific opportunities. We measured ratios of atomic polarizabilities ($\alpha_{\textrm{K}} / \alpha_{\textrm{Na}}$, $\alpha_{\textrm{Rb}} / \alpha_{\textrm {Na}}$ , and $\alpha_{\textrm{Rb}} / \alpha_{\textrm{K}}$) each with 0.3\% uncertainty. We also measured the ratios of van der Waals atom-surface interaction strengths ($C_3$ values) for Na, K, and Rb with 3\% uncertainty. Many sources of systematic uncertainty such as atomic velocity or surface geometry are common-mode and cancel out when reporting these ratios. Our measurements with a multi-species atom interferometer therefore serve as improved tests of atomic structure calculations. [Preview Abstract] |
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E1.00015: Atom Waveguides for Atom Chips William Golding Studies of the quantum behavior of magnetic atoms guided by two-dimensional quadrupole magnetic fields will be presented. The basic model is a particle with spin one-half that is guided by a quadrupole field of infinite longitudinal extent. The Schr\"{o}dinger equation for this spin one-half system is reduced to a pair of coupled second-order differential equations for the radial wavefunctions. These equations are uncoupled resulting in fourth-order differential equations that can be solved using Frobenius series techniques near the regular singular point that occurs at the origin. The four solutions to these equations represent four types of transverse waveguide mode. However, two solutions are not finite at the origin and are rejected as unphysical in this problem. The two finite solutions that remain provide a complete understanding of the guide mode structure close to the guide center. To complete the solutions and to obtain the transverse eigenvalues of the guide one can use numeric techniques along with asymptotic solutions to establish boundary conditions at large radii. In general, the solutions defined in this way are not pure bound states but have both a bound and an unbound character. However, by both exploiting a degeneracy at zero longitudinal field and transforming to a spin basis in which the quantization axis is defined to be everywhere parallel to the local field, states that are either purely bound or unbound can be constructed. [Preview Abstract] |
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E1.00016: The relative population distribution of atoms in the output ports of atom Michelson interferometers Ebubechukwu Ilo-Okeke, Alex Zozulya An atom Michelson interferometer uses off-resonant laser beams to split a cloud of Bose-Einstein condensate (BEC) into two clouds that travel along different paths and are recombined using identical splitting laser beams. Three clouds emerge after recombination. The population of atoms in each cloud gives an insight on the relative phase-shift accumulated by the atoms during their propagation. We derive an expression for the probability density of counting any number of atoms within the three different clouds, calculate the characteristic features of the probability density like the expectation value, the variance and the cross-correlation, discuss the dependence of the probability density and its characteristic features on the atomic interactions, and relate our results with experiment. [Preview Abstract] |
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E1.00017: BEC Precision Interferometry: Towards a Measurment of the DC Polarizability of 87Rb J.H.T. Burke, V. Leung, R.A. Horne, R.H. Leonard, C.A. Sackett We present our efforts to make precision measurements with a Bose-Einstein condensate guided-wave interferometer. In this case, a BEC of 87Rb is positioned between millimeter scale electric field plates such that a differential phase can be applied between two arms of an interferometer. This phase is proportional to the electric polarizability, which we anticipate measuring to an ultimate precision of four decimal places. We will discuss the motivations and apparatus considerations as well as preliminary results. [Preview Abstract] |
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E1.00018: Magnetic Control of Atomic Motion Tom Mazur, Travis Bannerman, Isaac Chavez, Rob Clark, Adam Libson, Mark Raizen Using a sequence of pulsed electromagnetic coils, known as the atomic coilgun, we slowed supersonic beams of atomic neon and molecular oxygen. We report our progress toward adapting the atomic coilgun for magnetically trapping hydrogen isotopes. This work has motivated us to investigate other methods for magnetic control of atomic motion. We describe these techniques, and present calculations suggesting their utility in controlling atomic motion. We then outline our plans for using these methods in certain applications. [Preview Abstract] |
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E1.00019: Through-chip high numerical aperture imaging of a BEC Evan Salim, Jonathan Pfeiffer, Daniel Farkas, Dana Anderson We present a chip based BEC apparatus that gives optical access to an atomic sample with numerical apertures as high as 0.8. We incorporate a window into a silicon chip that forms a wall of the vacuum chamber and makes it possible to place the primary objective of an imaging system as close as 600 microns from the atoms while the lens itself resides outside of the chamber. We show progress on our system, which allows for both high-resolution in-trap imaging of a BEC and projection of an optical potential in proximity of the chip surface with an off-the-shelf microscope objective. The system is designed to enable atom tunneling experiments with the ultimate goal of demonstrating an atom transistor using a triple-well potential. [Preview Abstract] |
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E1.00020: Cavity QED with trapped neutral atoms Chung-Yu Shih, Michael Gibbons, Michael Chapman Cavity QED systems consisting of neutral atoms coupled to high-finesse optical micro-cavities have important applications to quantum information processing. We have developed an experiment with trapped atoms in a high finesse cavity in the strong coupling regime. We have demonstrated loading and storage of atoms delivered from a magneto-optic trap to the resonator using two parallel atom conveyors. We will discuss the current progress on atoms-atoms interaction within the cavity, as well as future applications. [Preview Abstract] |
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E1.00021: A Compact, Microchip-Based, Atomic Clock Based on Ultracold Trapped Rb Atoms Daniel Farkas, Alex Zozulya, Dana Anderson We propose a compact atomic clock based on ultracold Rb atoms that are magnetically trapped near the surface of an atom microchip. An interrogation scheme that combines electromagnetically-induced transparency (EIT) with Ramsey's method of separated oscillatory fields can achieve atomic shot-noise level performance of 10$^{-13}$/$\tau ^{1/2}$ for 10$^{6}$ atoms and an interrogation time of 1 s. A two-color Mach-Zehnder interferometer can detect a 100 pW probe beam at the optical shot-noise level using conventional photodetectors. This measurement scheme is non-destructive and therefore can be used to increase operational duty cycle by reusing the trapped atoms between clock cycles. Numerical calculations of the density matrix equations are used to identify realistic operating parameters at which AC Stark shifts are eliminated. By considering fluctuations in these parameters, we estimate that AC Stark shifts can be canceled to a level better than 2$\times $10$^{-14}$. [Preview Abstract] |
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E1.00022: Photonic Phase Gate via an Exchange of Fermionic Spin Waves in a Spin Chain Alexey Gorshkov, Johannes Otterbach, Eugene Demler, Michael Fleischhauer, Mikhail Lukin We propose a new protocol for implementing the two-qubit photonic phase gate. In our approach, the $\pi$ phase is acquired by mapping two single photons into atomic excitations with fermionic character and exchanging their positions. The fermionic excitations are realized as spin waves in a spin chain, while photon storage techniques provide the interface between the photons and the spin waves. Possible imperfections and experimental systems suitable for implementing the gate are discussed. [Reference: arXiv:1001.0968] [Preview Abstract] |
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E1.00023: Simulating bosons in magnetic field with photonics Mohammad Hafezi, Mikhail Lukin, Eugene Demler, Edo Waks, Jacob Taylor We propose a 2D photonic system where the dynamics of photons are analogous to charged bosons in a magnetic field. We show that a magnetic field can be `simulated' for photons without using a magnetic field or any time-reversal symmetry breaking mechanism. We apply a technique to probe transport properties of such systems. In particular, the underlying energy spectrum is manifested in the transmission and reflection coefficients in form of a Hofstadter butterfly. We also discuss the effect of loss in such systems and investigate the system's robustness to impurities. [Preview Abstract] |
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E1.00024: Atom chip microscopy: A novel probe for strongly correlated materials Brian Kasch, Matthew Naides, Richard Turner, Ushnish Ray, Benjamin Lev Atom chip technology---substrates supporting micron-sized current-carrying wires that create magnetic microtraps near surfaces for thermal or degenerate gases of neutral atoms---will enable single-shot, large area detection of magnetic flux below the $10^{-7}$ flux quantum level. By harnessing the extreme sensitivity of Bose-Einstein condensates (BECs) to external perturbations, cryogenic atom chips could provide a magnetic flux detection capability that surpasses all other techniques by a factor of $10^2$--$10^3$. We describe the merits of atom chip microscopy, our Rb BEC and atom chip apparatus, and prospects for imaging strongly correlated condensed matter materials. [Preview Abstract] |
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E1.00025: Enhanced Longitudinal Confinement in an On-Chip Atom Wave-Guide via Optical Lensing of the Atomic Wave-Packet Jason Alexander, Violeta Prieto, Chris Rowlett, Patricia Lee, William Golding We report on progress at the Army Research Laboratory towards implementation of a compact and sensitive chip-based cold atom interferometer. The interferometer makes use of $^{87}$Rb atoms magnetically confined in a wave-guide near the surface of a lithographically patterned chip. Optical lensing effects in cold atom clouds have been recently demonstrated in free space for both a single Gaussian beam [1] and a moving optical lattice potential [2]. We will discuss a similar focusing and collimation of the atomic wave-packet in the chip wave-guide. This reverses the wave-packet broadening in the longitudinal direction of the wave-guide, and therefore improved contrast in interference fringes and signal-to-noise ratio can be expected. \\[4pt] [1] Zhou et al, Phys. Rev. A \textbf{80 }033411 (2009) \\[0pt] [2] Fallani et al, Phys. Rev. Lett. \textbf{91} 240405 (2003) [Preview Abstract] |
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E1.00026: ATOMIC AND MOLECULAR STRUCTURE AND PROPERTIES |
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E1.00027: Lifetimes and branching ratios of excited anion states Steven M. O'Malley, Donald R. Beck Relativistic configuration-interaction transition probability calculations have been performed for several anion cases of our recent lanthanide\footnote{S. M. O'Malley and D. R. Beck, Phys. Rev. A \textbf{79}, 012511 (2009).} and actinide\footnote{S. M. O'Malley and D. R. Beck, Phys. Rev. A \textbf{80}, 032514 (2009).} studies. In particular, we identified an E1 transition ($\sim$3680 nm) in La$^-$ that may prove more useful in laser-cooling applications than the previously proposed Os$^-$ candidate\footnote{A. Kellerbauer and J. Walz, New J. Phys. \textbf{8}, 45 (2006).}. We also explored long-lived states in Lu$^-$ and Lr$^-$ which are restricted to M2 decay by selection rules. Finally, we found sufficient mixing between a weakly-bound alternate-configuration Pr$^-$ level and a nearby resonance to result in a lifetime (M1/E2) similar to other excited levels despite a two-electron difference between the dominant configurations. The details of the Pr$^-$ calculations serve as further confirmation of the utility of our universal $jls$ restrictions on $4f^n$ and $5f^n$ portions of lanthanide and actinide wave functions, but we find that a similar application to $d^k$ electron subgroups in transition metals (Os$^-$) has a much smaller impact on the complexity of our calculations. [Preview Abstract] |
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E1.00028: Polarization Measurement in an Optical DipoleTrap Fang Fang, David Vieira, Xinxin Zhao Optical trapping of radioactive atoms has a great potential in precision measurements for testing fundamental physics such as electric dipole moment (EDM), atomic parity non-conservation (PNC) and parity violating beta-decay correlation coefficients. One challenge that remains is to polarize the atoms to a high degree and to measure the polarization of the sample and its evolution over time. We report on the polarization study of Rb atoms in a yttrium-aluminum-garnett (YAG) laser optical dipole trap using resolved Zeeman spectroscopy techniques. We have prepared a cold cloud of polarized atoms to 97{\%} by optical pumping in the YAG dipole trap. The spin polarization is further purified to 99{\%} and maintained when the two-body collision loss rate between atoms in mixed spin states is greater than the one-body trap loss. These advancements are an important step towards a new generation of precision measurement with polarized trapped atoms. [Preview Abstract] |
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E1.00029: Spectroscopy of high-L Rydberg levels of nickel Julie A. Keele, Shannon L. Woods, Mark E. Hanni, Kristen Voigt, Stephen R. Lundeen The complex fine structure pattern in high-L ( L $>$ 4) Rydberg levels of nickel were studied using the Resonant Excitation Stark Ionization Spectroscopy (RESIS) technique. A beam of Ni$^{+}$ ions, obtained from a Colutron ion source, captured a single electron from a Rb 9F Rydberg target to become highly excited Rydberg levels of neutral Ni. Levels with n=9 and L=5,6,7, and 8 were excited to n=19 or 20 using a Doppler-tuned CO$_{2}$ laser, resolving the n=9 fine structure pattern, which consists of six levels for each value of L. Analysis of the pattern using the long-range polarization model determined several properties of the 3d$^{9}$ $^{2}$D$_{5/2}$ ground state of Ni$^{+}$, including its permanent quadrupole moment and its scalar and tensor dipole polarizabilities. [Preview Abstract] |
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E1.00030: Inner-shell ionization of atomic targets by Electron Impact A.K.F. Haque, M.R. Talukder, M. Shahjahan, M.A. Uddin, A. K. Basak, B.C. Saha The knowledge of inner-shell ionization cross sections has not only fundamental importance for understanding collision dynamics of electron-atom interactions, \textit{etc}, but also is used extensively in many applied fields such as radiation science, astrophysics, plasma physics, \textit{etc}. The enormous demands of ionization cross sections can only be met by suitable analytical formula that are easy to use and can produce reliable result. We report here an extension of the CVTS [1] model incorporating both the relativistic and ionic factors and tested on 23 atomic targets ranging from He to U [2] with excellent account of the experimental cross sections. \\[4pt] [1] C. S. Campos, M. A. Z. Vasconcellos, J. C. Trincavelli, and S. Segui, J. Phys. B. 40, 3835 (2007).\\[0pt] [2] A K F Haque, M R Talukder, M. Shahjahan, M A Uddin, A K Basak and B C Saha, J. Phys. B.; \textit{At. Mol. Opt. Phys} (under consideration), (2010). [Preview Abstract] |
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E1.00031: Site - Selective Ionization and Relaxation Dynamics in Heterogeneous Nano - Systems Matthias Hoener, Daniel Rolles, Alejandro Aguilar, Rene Bilodeau, David Esteves, Paul Olalde Velasco, Eddie Red, Zoran Pesic, Nora Berrah We investigated energy and charge transfer mechanisms as well as fragmentation dynamics in site-selectively ionized heterogeneous core-shell clusters using a high-resolution photoelectron - ion coincidence technique. We show that after inner-shell photoionization, energy or charge is transferred to neighboring atoms and that the subsequent charge localization depends on the site of ionization. Cluster bulk ionization leads to more distinct fragmentation channels than surface ionization. We attribute this to different electronic decay, charge localization and fragmentation times and conclude that charge transfer and fragmentation dynamics are strongly influenced by the environment of the initially ionized atom. [Preview Abstract] |
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E1.00032: Atomic Spectra Bibliography Databases at NIST Alexander Kramida NIST's Atomic Spectroscopy Data Center maintains three online Bibliographic Databases (BD) [http://physics.nist.gov/PhysRefData/ASBib1/index.html]: -- Atomic Energy Levels and Spectra (AEL BD), Atomic Transition Probability (ATP BD), and Atomic Spectral Line Broadening (ALB BD). This year marks new releases of these BDs -- AEL BD v.2.0, ATP BD v.9.0, and ALB DB v.3.0. These releases incorporate significant improvements in the quantity and quality of bibliographic data since the previous versions published first in 2006. The total number of papers in the three DBs grew from 20,000 to 30,000. The data search is now made easier, and the returned content is enriched with direct links to online journal articles and universal Digital Object Identifiers. Statistics show a nearly constant flow of new publications on atomic spectroscopy, about 600 new papers published each year since 1968. New papers are inserted in our BDs every two weeks on average. [Preview Abstract] |
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E1.00033: Characterization of X-Ray FEL Beam Properties at the LCLS AMO Station With FLASH GMD and Wavefront Sensor Pavle Juranic, Ulf Jastrow, Svea Kapitzki, Stefan Moeller, Jacek Krzywinski, John Bozek, Uwe Kroth, Hendrik Schoeppe, Stefan Hau-Rige, Bernhard Floeter, Klaus Mann, Matthias Richter, Andrey Sorokin, Kai Tiedtke As a part of an international effort to measure beam properties of FELs, a protocol for a collaborative set of measurements was set up between groups from the LCLS [1], FLASH [2], Germany, and SCSS in Japan [3], meant to perform tests to evaluate their measurement devices against one another. This report showcases the measurements performed at the LCLS AMO end station using the FLASH Gas Monitor Detector (GMD) [4] and the wavefront sensor developed for the X-ray region by the Laser Laboratory in Goettingen, Germany. Both of these devices were originally designed to operate at photon energies between 10-100 eV, but were redesigned for operation at higher photon energies, and tested for the first time at energies between 800 and 1000 eV at LCLS. This results of these studies are presented here. [1] Linac Coherent Light Source (LCLS) SLAC Desigh Study Report No. SLAC-R-521, 1998. [2] W. Ackermann \textit{et al}, Nat. Photonics \textbf{1 }(2007) 336. [3] T. Shintake \textit{et al}, Nat. Photonics \textbf{2 }(2008) 555. [4] K. Tiedtke \textit{et al}, J. Apl. Phys. \textbf{103 }(2008) 094511. [Preview Abstract] |
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E1.00034: Optical transition of the $^{229}$Th nucleus in a solid-state environment Wade Rellergert, Scott Sullivan, Radoyeh Shojaei, David DeMille, Richard Greco, Markus Hehlen, Justin Torgerson, Eric Hudson We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric state in $^{229}$Th. Since nuclear transitions are far less sensitive to environmental conditions than atomic transitions, we argue that the $^{229}$Th optical nuclear transition may be driven inside a host crystal with a high transition Q. This technique might also allow for the construction of a solid-state optical frequency reference that surpasses the precision of current optical clocks, as well as improved limits on the variability of fundamental constants. Based on analysis of the crystal lattice environment, we argue that a precision of $ 3 * 10^{ - 17 } < \Delta f/f < 1 * 10^{ - 15 }$ after 1~s of photon collection may be achieved with a systematic-limited accuracy of $\Delta$f/f $\sim$ 2 * 10$^{ - 16 }$. Improvement by a factor of 10$^2$ to 10$^3$ of the constraints on the variability of several important fundamental constants also appears possible. We report on progress towards evaluation of candidate host crystals. [Preview Abstract] |
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E1.00035: Non-linear coupled microwave and mechanical resonators Prabin Adhikari, Mohammad Hafezi, Jacob Taylor Optomechanical systems provide an intriguing test bed for examining concepts such as cooling a macroscopic quantum system to its ground state, and also for practical applications like squeezing and quantum information processing. A key difficulty at present is the weakness of the radiation pressure force in the optical domain at the single photon level. However, this changes in the microwave domain. To test this, we theoretically investigate a system, consisting of two coupled oscillators (photonic and phononic). We focus on the non-linear properties of the system and its potential implementation based on current experimental approaches, and show applications to metrology and quantum information science. [Preview Abstract] |
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E1.00036: Symmetries and configurations of a molecular quantum system composed with four identical nuclei Nicolas Douguet, Elie Assemat, Viatcheslav Kokoouline We discuss in details the symmetry of a molecular system of four identical nuclei, surrounded by electronic clouds, shaped as different well separated fragments at large distances from one to another. Namely we will consider respectively the system as (1) two dimers, (2) a trimer and a free particle and (3) a dimer and two free particles. Our general approach to treat this problem consists at first on exhibiting the form of the eigenspaces of the large distance Hamiltonian, labeled by constants of motion of the system, for each configuration. The study of the symmetry of the system can then be performed by decomposition of these subspaces in irreducible representations of the total symmetry group $G_{48}$ of four identical particles via the different sub-groups of symmetry of the large distance Hamiltonian. The obtained results could be for instance a basis of interest to study the different recombinations or break down of four identical particles after collisions allowed by symmetry conservation. Selection rules, as well as allowed quantum states respecting the fermionic or bosonic nature of the particles, can be explicitly determined from these results. [Preview Abstract] |
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E1.00037: Carrier-envelope phase effect on the asymmetric $\mathrm{H_{2}^{+}}$ dissociation in an ultrashort pulse using Floquet theory Shuo Zeng, B.D. Esry The tilted structure of the asymmetry pattern of $\mathrm{H_{2}^{+}}$dissociation as a function of carrier-envelope phase (CEP) and nuclear kinetic energy release (KER) at low energies (0 $\sim$3eV) has been seen both theoretically [1] and experimentally [2, 3]. We present a method to interpret this tilted structure using a Floquet-like theory [1]. In this formalism, it is convenient to rewrite the contribution of a given Floquet channel $\mathrm{n}$ to the KER spectrum in polar form with phase $\delta_{n}(E)$ , where $\mathrm{E}$ is the KER, which enables us to explain the tilt as a result of the interference between different channels. Our calculations demonstrate the dependence of the asymmetry pattern on wavelength, duration and CEP.\\[4pt] [1] J.J.Hua \textit{et al.}, J. Phys. B 42 085601 (2009)\\[0pt] [2] Manuel Kremer \textit{et al.}, Phys. Rev. Lett. 103.213003 (2009)\\[0pt] [3] M.F.Kling \textit{et al.}, Mol. Phys. (2008) [Preview Abstract] |
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E1.00038: Group theoretical analysis of nitrogen-vacancy center's energy levels and selection rules Jeronimo Maze, Adam Gali, Emre Togan, Yiwen Chu, Alexei Trifonov, Efthimios Kaxiras, Mikhail Lukin Defect in solids such as the nitrogen-vacancy center in diamond are promising candidates for high precision measurements, quantum information and quantum communication. A vast knowledge of their complicated dynamics is essential to effectively implement these applications. Here, we show that group theoretical analysis can be successfully used to unravel the properties of any point defect in solids. In particular, we work out in detail the energy levels and selection rules of the nitrogen-vacancy center and show how they can be implemented in applications such as spin-photon entanglement, an essential step towards quantum communication. Furthermore, we analyze the performance of these properties under perturbations that reduce the symmetry of the defect such as strain and electric field. We provide useful guidance on how to overcome these undesired perturbations and compare our model with recent experimental results. [Preview Abstract] |
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E1.00039: Producing and Trapping cold molecular NO Parshuram Dahal, Bryan Bichsel, Jason Alexander, James Coker, John Furneaux, Michael Morrison, Neil Shafer-Ray, Eric Abraham We present the production of cold samples of Nitric Oxide (NO) in the lowest ro-vibrational state. The sample is produced by the extraction of the cold fraction of the Maxwell -- Boltzman distribution of a thermal source. The temperature of the resulting gas (T $\sim $ 2 K) is measured by electric field stabilized, Rydberg time-of-flight. Results of a new source for cold molecular production using activated carbon is presented, which may eliminate the need for ablation loading in buffer gas cooling experiments. Progress toward magnetically trapping NO will be discussed. [Preview Abstract] |
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E1.00040: Stern-Gerlach Dynamics with Quantum Propagators Jean-Francois S. Van Huele, Bailey C. Hsu, Manuel Berrondo We study the quantum dynamics of a nonrelativistic neutral particle with spin in an inhomogeneous external magnetic field. We first consider fields with one-dimensional inhomogeneities, both unphysical and physical, and construct the corresponding analytic propagators. We then consider fields with two-dimensional inhomogeneities and develop an appropriate numerical propagation method. We propagate various initial states, both pure and mixed, and find the evolution of their spin densities. We identify characteristic features of spin density dynamics and focus on non-ideal Stern-Gerlach outcomes. [Preview Abstract] |
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E1.00041: {\it Ab initio} potential energy surfaces $1 ^4A'$, $2 ^4A'$, $1 ^4A''$ and $2 ^4A''$ of Li$_3$ in a constant external magnetic field Juan Blandon, Xuan Li, Daniel Brue, Gregory Parker Molecular potentail energy surfaces (PESs) have played an essential role in understanding the field-induced interactions in atomic/molecular systems. External magnetic fields are relevant because they are used to control the pairwise interactions in atomic quantum gases. We present accurate PESs for three fermionic $^6$Li atoms under a constant external magnetic field. Calculations are made using the diatomics-in-molecules method [1], accounting for fine and hyperfine interactions. PESs are constructed using full configuration interaction for the three valence electrons, and a global-fit method [2] is used to obtain the three-body terms. These PESs can be used, for example, to study three-body recombination near overlapping Feshbach resonances. \\[4pt] [1] J. C. Tully, J. Chem. Phys. {\bf 58}, 1396 (1973) \newline [2] A. Aguado {\it et al.}, Comput. Phys. Commun. {\bf 108}, 259 (1998) [Preview Abstract] |
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E1.00042: The hyperfine Stark effect of the $6d \, ^2 \! D_{3/2}$ and $7d \, ^2 \! D_{3/2}$ states of cesium measured using two-photon laser spectroscopy in a thermal beam Andrew Kortyna, Jennifer Grab The hyperfine Stark effect of $6d \, ^2 \! D_{3/2}$ and $7d \, ^2 \! D_{3/2}$ states of $^{133}$Cs are studied using resonantly-enhanced laser spectroscopy. Two single-mode external-cavity diode lasers counter-propagate through a well collimated thermal beam of cesium. This interaction region is centered between two parallel field plates. The $nd$ states are resonantly excited through the $6p \, ^2 \! P_{1/2}$ intermediate state and are detected with either laser-induced-fluorescence or photo-ionization by a pulsed laser. The relative frequency scale is calibrated in real-time by phase modulating the $6p \, ^2 \! P_{1/2} \rightarrow nd$ laser at precise frequencies. The absolute frequency is referenced to the two-photon transition measured in a field-free absorption cell of cesium vapor. The Stark shift of the hyperfine states and their magnetic sublevels are fitted to perturbation theory to find the scalar and tensor polarizabilities. [Preview Abstract] |
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E1.00043: Supersonic expansions of molecular oxygen Jesus Perez-Rios, Marta Isabel Hernandez, Guzman Tejeda, Salvador Montero Supersonic jets are gas dynamic quasi-universal structures showing a wealth of features combining laminar and turbulent flow, relaxation effects, shock waves, vortices, slip effects, and condensation, spanning a wide range of densities, temperatures, chemical species, and Kn numbers.In the supersonic expansion exists a zone between the nozzle and the shock wave, called the zone of silence. We apply the Raman spectroscopy in this zone to obtain the experimental number density and the population of therotational levels. This method has a high special resolution ($<$5$\mu $m) and high-sensitivity spectroscopy ($<$photon/sec). These measures allow us to compare the theory with the experiment using the master equation (derived from the Boltzmann equation).In this work we apply this experimental technique to a molecular oxygen expansion, showing a good agreement between theory (where we have used the PES obtained by M. Bartolomei; et al.) and the experiment. [Preview Abstract] |
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E1.00044: Atom Wavelike Nature Solved Mathematically Charles Sven Like N/S poles of a magnet the strong force field surrounding, confining the nucleus exerts an equal force [noted by this author] driving electrons away from the attraction of positively charged protons force fields in nucleus -- the mechanics for wavelike nature of electron. Powerful forces corral closely packed protons within atomic nucleus with a force that is at least a million times stronger than proton's electrical attraction that binds electrons. This then accounts for the ease of electron manipulation in that electron is already pushed away by the very strong atomic N/S force field; allowing electrons to drive photons when I strike a match. Ageless atom's electron requirements, used to drive light/photons or atom bomb, without batteries, must be supplied from a huge, external, super high frequency, super-cooled source, undetected by current technology, one that could exist 14+ billion years without degradation -- filling a limitless space prior to Big Bang. Using only replicable physics, I show how our Universe emanated from that event. [Preview Abstract] |
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E1.00045: The high-energy satellites of L$\alpha _{2}$ X-Ray transition in higher-Z atoms Surendra Poonia The X-ray satellite spectra arising due to 2p$_{3/2}^{-1}$3x$^{-1}$-3x$^{-1}$3d$^{-1}$ (x$\equiv $s,p,d) transition array, in elements with Z=73 to 90, have been calculated. The energies of various transitions of the array have been determined by using available Hartree-Fock-Slater data on 1s$^{-1}$-2p$^{-1}$3x$^{-1}$ and 2p$_{3/2}^{-1}$-3x$^{-1}$,3x'$^{-1}$ Auger transition energies and their relative intensities have been estimated by considering cross - sections of singly ionized 2x$^{-1}$ (x $\equiv $ s, p) states and then of subsequent Coster-Kronig and shake off processes. The calculated spectra have been compared with the measured satellite energies in L$\alpha _{2}$ spectra. It has been established that one satellite observed in the L$\alpha _{2}$ region of the X-ray spectra of various elements and named $\alpha _{s }$in order of increasing energy are mainly emitted by 2p$_{3/2}^{-1}$3d$^{-1}$-3d$^{-2}$ transitions. It is observed that the satellite $\alpha _{s}$ in all these spectra can be assigned to the superposition of three intense transitions namely $^{3}$P$_{1}-^{3}$D$_{1}$, $^{3}$D$_{2}-^{3}$D$_{3}$ and $^{3}$D$_{2}-^{3}$D$_{1}$. The three remaining satellites in $_{80}$Hg namely La$_{13}$, La$_{14}$ and La$_{17}$ are found to have different origin in different elements. [Preview Abstract] |
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E1.00046: Theoretical predictions of the shapes and parameters of $\gamma _{1}\prime$ satellites L-X-Ray lines of 4d transition elements Surendra Poonia The X-ray satellite spectra arising due to 2p$_{1/2}^{-1}$3x$^{-1}$-3x$^{-1}$4d$_{3/2,5/2}^{-1}$ (x $\equiv $ s, p, d), i.e. L$_{2}$M$_{x}$-M$_{x}$N$_{4,5}$ transition array, in elements with Z = 41 to 51, have been calculated, using available Hartree-Fock-Slater data on K-L$_{2}$M$_{x}$ and L-M$_{x}$N$_{4,5}$ Auger transition energies. The relative intensities of all the possible transitions have been estimated by considering cross - sections for the Auger transitions simultaneous to a hole creation and then distributing statistically the total cross sections for initial two hole states L$_{2}$M$_{x}$ amongst various allowed transitions from these initial states to M$_{x}$N$_{4,5}$ final states by Coster-Kronig (CK) and shake off processes. In both these processes initial single hole creation is the prime phenomenon and electron bombardment has been the primary source of energy. On the basis of agreement between computed spectra and measured satellites, It is observed that the satellite L$\gamma _{1}\prime _{ }$in $_{41}$Nb to $_{51}$Sb is emitted by the superposition of the most intense transitions namely L$_{2}$M$_{1}$ $^{1}$P$_{1}$-M$_{1}$N$_{4} \quad ^{1}$D$_{2}$, L$_{2}$M$_{1}$ $^{3}$P$_{0}$-M$_{1}$N$_{4} \quad ^{3}$D$_{1}$,L$_{2}$M$_{3}$ $^{3}$D$_{1}$-M$_{3}$N$_{5} \quad ^{3}$D$_{1}$ and L$_{2}$M$_{3}$ $^{3}$D$_{1}$-M$_{3}$N$_{4} \quad ^{3}$P$_{0}$ contributing in order of decreasing intensity. [Preview Abstract] |
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E1.00047: ABSTRACT WITHDRAWN |
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E1.00048: SPECTROSCOPY, LIFETIMES, OSCILLATOR STRENGTHS |
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E1.00049: Laboratory Demonstration of a Green Astro-comb Chih-Hao Li, Alex Glenday, David F. Phillips, Sylvain Korzennik, Guoqing Noah Chang, Andrew Benedick, Li-Jin Chen, Franz X. Kaertner, Dimitar Sasselov, Andrew Szentgyorgyi, Ronald Walsworth Searches for extrasolar planets using the periodic Doppler shift of stellar lines are approaching Earth-like planet sensitivity. Astro-combs, a combination of an octave spanning femtosecond laser and a mode-filtering cavity provide a likely route to increased calibration precision and accuracy. Initial astro-comb demonstrations have been performed in the near infrared where broadband lasers are available. Here we present initial laboratory results on a ``green'' astro-comb providing approximately 50 nm of stable astro-comb light centered near 550 nm. Light from a 1 GHz, octave-spanning Ti:Sapphire laser is broadened in a photonic crystal fiber optimized to produce light in the green. This 1 GHz spaced green light is then filtered to roughly 30 GHz mode spacing via a Fabry-Perot cavity with ultra-low dispersion mirrors. Current progress on the characterization of this green astro-comb will be presented. [Preview Abstract] |
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E1.00050: Calibration of an Astrophysical Spectrograph with an Astro-comb David F. Phillips, Alex Glenday, Chih-Hao Li, Claire Cramer, Sylvain Korzennik, Guoqing Noah Chang, Li-Jin Chen, Andrew Benedick, Franz X. Kaertner, Dimitar Sasselov, Andrew Szentgyorgyi, Ronald L. Walsworth Searches for extrasolar planets using the periodic Doppler shift of stellar lines are approaching Earth-like planet sensitivity. To find a 1-Earth-mass planet in an Earth-like orbit, an order of magnitude improvement in state-of-the-art radial velocity spectroscopy is necessary. An astro-comb, the combination of an ocatve-spanning laser frequency comb with a Fabry-Perot cavity, producing evenly spaced frequency markers with the potential for large wavelength coverage is a promising avenue towards improved wavelength calibration. Here we demonstrate the calibration of a high-resolution astrophysical spectrograph below the 1 m/s level in the 800-900 nm spectral band using an octave-spanning Ti:Sapphire laser and an ultra-low dispersion Fabry-Perot filter cavity adjusted for a mode spacing of approximately 31 GHz. Modeling of spectrograph response function and overall system stability and reproducibility will be described. [Preview Abstract] |
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E1.00051: Excitation energies, radiative and autoionization rates, dielectronic satellite lines, and dielectronic recombination rates for excited states of Ag-like W from Pd-like W W.R. Johnson, U.I. Safronova, A.S. Safronova Energy levels, radiative transition probabilities, and autoionization rates for [Kr]$4d^94fnl$, [Kr]$4d^95l'nl$, ($n$=5-8), and [Kr]$4d^96lnl$ ($n$=6-7) states in Ag-like tungsten (W$^{27+}$) are calculated using the relativistic many-body perturbation theory method (RMBPT code), the Multiconfiguration relativistic Hebrew University Lawrence Atomic Code (HULLAC code), and the Hartree-Fock-Relativistic method (COWAN code). We continue systematic studies of RMBPT data for tungsten ions and important comparison with other codes. Branching ratios relative to the first threshold and intensity factors are calculated for satellite lines, and dielectronic recombination (DR) rate coefficients are determined for the singly-excited [Kr]$4d^{10}nl$ ($n$=5-7). The total DR rate coefficient is derived as a function of electron temperature. These atomic data are important in modeling of N-shell radiation spectra of heavy ions generated in various collision as well as plasma experiments. The tungsten data are particulary important for fusion application. [Preview Abstract] |
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E1.00052: Atomic Ytterbium Beam Experiments at an Undergraudate Physics Laboratory Martin Madsen, R. Paudel, L.W. Lupinski, J.E. Barlow, S.E. Pond We report our progress towards producing a beam of cold Ytterbium atoms in an undergraduate laboratory. We constructed a low-cost Zeeman slower designed to slow Yb atoms from 325 m/s to $\sim$ 1 cm/s on the $^{1}S_{0}$ to $^{1}P_{1}$ atomic transition, accessible by a direct-diode laser at 398.8 nm. We propose a number of atomic beam experiments for undergraduate labs including measuring the ytterbium isotope shift, and measuring both power and Doppler broadening of a single isotope. We also propose using the spectrally-resolved spontaneous emission from a long-lived decay channel ($\tau\sim$ 1~$\mu$s) to measure the Yb beam velocity. [Preview Abstract] |
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E1.00053: Atomic transition probabilities of Ce I from Fourier transform spectra D.E. Nitz, J.E. Lawler, J. Chisholm, M.P. Wood, J. Sobeck, E.A. Den Hartog We report transition probabilities for 2874 lines of CeI in the wavelength range 360 -- 1500 nm. These are derived from new branching fraction measurements on Fourier transform spectra normalized with recently-reported radiative lifetimes (Den Hartog et al., J. Phys. B 42, 085006 (2009)). We have analyzed the decay branches for 153 upper levels in 14 different spectra recorded under a variety of discharge lamp conditions. Comparison of results with previous less extensive investigations shows good agreement for lines studied in common. Accurate Ce I transition probabilities are needed for applications in astrophysics and in lighting research, particularly for the development of improved metal halide high-intensity discharge lamps. [Preview Abstract] |
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E1.00054: Femto-second Frequency Comb Spectroscopy of Ytterbium Ions Martin Schauer, Jeremy Danielson, Saidur Rahaman, Michael Schacht, Baozhou Sun, Jiepeng Zhang, Xinxin Zhao, Justin Torgerson Forbidden optical transitions in trapped ions are of great interest for high precision spectroscopic applications. We report on work to drive the $^{2}$S$_{1/2}$(F=0) -- $^{2}$D$_{3/2}$(F=2) electric quadrupole transition in $^{171}$Yb$^{+}$ ions with light derived directly from a femto-second frequency comb. To this end we have trapped and laser-cooled a single $^{171}$Yb$^{+}$ ion and minimized its driven micromotion. We have developed the infrastructure to manipulate and measure the quantum state of the ion, and we have produced light at the quadrupole transition wavelength of 435.5 nm by means of a femtosecond frequency comb. We will present results from all of this work as well as initial measurements of the quadrupole transition. [Preview Abstract] |
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E1.00055: Multiply charged thorium ions for nuclear laser spectroscopy Michael V. DePalatis, Corey J. Campbell, Layne R. Churchill, Dave E. Naylor, Alexander Radnaev, Michael S. Chapman, Alex Kuzmich Coherent excitation of the electronic states of atoms and molecules with lasers is at the heart of modern spectroscopy and metrology. To extend these techniques to nuclear states would be a tremendous advance. However, the typical excitation energies for nuclear matter are in the keV to MeV energy range, out of reach of modern coherent radiation sources. In the unique case of the $^{229}$Th nucleus, the energy splitting of the ground state doublet is only several eV,\footnote{L. A. Kroger {\&} C. W. Reich, \textit{Nucl. Phys. A} \textbf{259}, 29 (1976). } which may be within the reach of coherent table-top UV lasers. Previously we demonstrated the direct laser cooling of $^{232}$Th$^{3+}$ in an rf Paul trap,\footnote{C. J. Campbell {\it et al.}, {\it Phys. Rev. Lett} {\bf 102}, 233004 (2009).} an important first step towards nuclear laser spectroscopy. Here we report progress towards loading and trapping $^{229}$Th$^{3+}$ from a Thorium nitrate source. [Preview Abstract] |
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E1.00056: Circular Dichroism of RbHe and RbN$_{2}$ Molecules Brian Lancor, Earl Babcock, Robert Wyllie, Thad Walker Spin exchange optical pumping (SEOP) is a method for producing spin polarized $^{3}$He through collisional transfer of angular momentum from an optically pumped Rb vapor. A long standing concern is that SEOP is much less efficient than theoretically predicted; it takes more laser power to polarize a given number of $^{3}$He nuclei than expected. We have investigated the effect of Rb-He and Rb-N$_{2 }$collisions on the quality of the dark state necessary for efficient optical pumping. N$_{2}$ and $^{3}$He collisions break the angular momentum selection rules and make the dark state weakly absorbing. With direct transmission measurements of a probe beam propagating through highly polarized atoms, along with precise Rb spin polarization measurements, we have deduced the circular dichroism for Rb with $^{3}$He and N$_{2 }$buffer gasses. Simulations show that the molecular absorption of pump light by atoms in the nominally dark ground state accounts for a significant amount of the observed inefficiency, particularly with broadband pump sources. [Preview Abstract] |
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E1.00057: Hyperfine-induced Intercombination Transitions in $^3$He Qixue Wu, Gordon W.F. Drake It is well known that hyperfine structure can induce transitions that are otherwise forbidden, or strongly suppressed, in heliumlike ions. We have recently found that, even in neutral helium-3, hyperfine structure can induce spin-forbidden intercombination transitions involving the higher-lying Rydberg states. In this paper we present high precision variational calculations of hyperfine-induced transitions $n\;^1$D$\rightarrow$$n'\;^3$P and $n\;^3$D$\rightarrow$$n'\;^1$P ($n=3-10,\,n'=2-9$) for $^3$He. Comparable strengths of hyperfine-induced transitions to normal E1 transitions are predicted. Conversely, normally allowed transitions can be strongly suppressed by hyperfine structure, as previously discussed and observed experimentally [1], such as $n\,^3\rm{D}_1,F=3/2$ $\rightarrow$ $2\,^3\rm{P}_2,F=5/2$.\\[4pt] [1] I.A. Sulai et al. Phys.\ Rev.\ Lett.\ {\bf 101}, 173001 (2008). [Preview Abstract] |
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E1.00058: Berry-like phases in structured atoms and molecules Edmund Meyer, Aaron Leanhardt, Eric Cornell, John Bohn Quantum mechanical phases arising from a periodically varying Hamiltonian are considered. These phases are derived from the eigenvalues of a stationary, ``dressed'' Hamiltonian that is able to treat internal atomic or molecular structure in addition to the time variation. In the limit of an adiabatic time variation, the usual Berry phase is recovered. For more rapid variation, nonadiabatic corrections to the Berry phase are recovered in perturbation theory, and their explicit dependence on internal structure emerges. Simple demonstrations of this formalism are given, to particles containing interacting spins, and to molecules in electric fields. [Preview Abstract] |
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E1.00059: Laser Spectroscopy of bi-alkali molecules Sourav Dutta, A. Altaf, J. Lorenz, D. Elliott, Yong Chen We report a study of laser spectroscopy of bi-alkali molecules, such as Li$_{2}$, Rb$_{2}$ and LiRb (work is in progress). We have constructed a dual-species (Li/Rb) heat pipe oven with a side viewport. The molecular fluorescence is excited by a dye laser with Rh6G dye (operating between 564 nm and 610 nm) and various home-made diode lasers (operating near 635 nm and 665 nm). The fluorescence is recorded using a $\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 4$} $ m monochromator with a 0.1 nm ($\sim $ 3 cm$^{-1})$ spectral resolution. Transitions to the X$^{1}\Sigma _{g}^{+}$ in Li$_{2}$ and Rb$_{2}$ have been measured and studies on LiRb are in progress. Molecular parameters, such as force constant, may be obtained from the analysis of the data (which agree with previously known values to within $\sim $ 3{\%}). Using the known values of dissociation energy D$_{e}$ and harmonic frequency $\omega _{e}$ for the alkali dimers, we also demonstrate that simple calculations with Morse potential approximation can be used to estimate the molecular transition wavelengths to within a few (1-3) nanometers from the experimentally measured values. Such information will aid in creating cold molecules via photoassociation in a dual species magneto-optical trap (LiRb in our case). [Preview Abstract] |
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E1.00060: Study of population redistribution in neon by laser optogalvanic spectroscopy Naveed Piracha, M. Aslam Baig Using neon hollow cathode lamp and employing two different experimental techniques, we have studied population redistribution in neon energy levels as a result of laser excitation. This work has also enabled us to measure effective lifetimes of the 1s$_{i}$ and the 2p$_{j}$ states. [Preview Abstract] |
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E1.00061: Spectroscopy of L-shell Cu ions Arati Dasgupta, Ward Thornhill, John Giuliani, Jack Davis, Robert Clark, Brent Jones, Dave Ampleford, Stephanie Hansen, Chris Jennings, Christine Coverdale, Greg Rochau, James Bailey, Mike Cuneo Radiation from Cu wire array Z pinches can have photon energies exceeding 8 keV. Experimental investigations of pinches on the Sandia National Laboratories Z machine using Cu arrays have already begun and more are planned for the near future. Diagnostics based on L-shell emissions are inherently more difficult than those for K-shell emissions, but they provide much more information about the L-shell experimental ionization dynamics and the extent to which a Z-pinch plasma approaches temperatures and densities required for significant K-shell x-ray production. We will analyze the ionization dynamics and generate K- and L-shell spectra for Cu using temperature and density conditions obtained from non-LTE radiation hydrodynamics simulations of experimental data. These results will be compared with K- and L-shell experimental spectra of Cu wire arrays imploded on the Sandia Z machine. Our self-consistent atomic model employs an extensive atomic level structure and data for all dominant atomic processes coupled with hydrodynamics and radiation transport to accurately model the spectroscopic details of the emitted radiation. [Preview Abstract] |
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E1.00062: MOLECULAR PHOTOIONIZATION, PHOTODETACHMENT, AND PHOTODISSOCIATION PROCESSES |
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E1.00063: Double Photoionization of Molecular Nitrogen Ralf Wehlitz, Timothy Hartman We have investigated the double photoionization process of molecular nitrogen using monochromatized synchrotron radiation and ion time-of-flight spectrometry. Although the doubly charged N$_{2}$ parent ions have the same mass-to-charge ratio as the singly charged atomic-nitrogen ions, both species exhibit a different width in the ion time-of-flight spectrum because the molecular ions do not move (except for the thermal motion) in contrast to the atomic fragment ions. Due to the break-up motion of the atomic nitrogen ions, the corresponding peak appears as a broad line in the spectrum whereas the molecular ions show up as a narrow peak. The different peak widths allowed us to separate both processes and enabled us to derive the molecular double-to-single photoionization ratio of N$_{2}$ over a large photon energy range. [Preview Abstract] |
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E1.00064: A quantum-trajectory approach for the full dynamics of polyatomic molecules in strong laser fields Zhongyuan Zhou, Shih-I Chu A quantum-trajectory approach is developed for the study of full dynamics of polyatomic molecules in strong laser fields. In this approach, the particles (electrons and nuclei) are characterized by the time-dependent coherent states and the particle trajectories are described by the positions and momenta of the coherent states. The basic equation is a group of coupled Hamilton Canonical equations for the trajectories. As a demonstration, we apply this approach together with Monte Carlo technique to study full dynamics of H$_{2}$ in strong laser fields. The energy-angular distribution of the probabilities of ionization, dissociation, and Coulomb explosion are calculated. The results are in fair agreement with available experimental and other theoretical results. The behaviors of H$_{2}$ in long-wavelength laser fields are also explored. The results show the low-energy structure of photoelectron spectra and behaviors of the structure change with laser wavelength and intensity as observed in recent experiments. [Preview Abstract] |
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E1.00065: Atom-fullerene hybridization, giant enhancement and correlation confinement resonances in the photoionization of Xe@C$_{60}$ Matthew McCune, Hopper Dale, Himadri Chakraborty, Mohamed Madjet, Jan Michael Rost, Steve Manson A detailed theoretical study of the subshell photoionization of Xe endohedrally confined in C$_{60}$ is presented. A powerful hybridization of the Xe $5s$ state with the bottom edge of C$_{60} \quad \pi $ band is found. Cross sections of these hybrid states exhibit rich structures and are radically different from the cross sections of free atomic or fullerene states [1]. The hybridization also affects the angular distribution asymmetry parameter of Xe $5p$ ionization near the Cooper minimum. The Xe $5p$ cross section, on the other hand, is greatly enhanced by borrowing considerable oscillator strength from the C$_{60}$ giant plasmon resonance [2]. Beyond the plasmon energy range the Xe subshell cross sections display confinement-induced oscillations in which, over the large $4d $shape resonance region, the dominant $4d $oscillations induce their ``clones'' in all degenerate weaker channels known as correlation confinement resonances. [1] H. S. Chakraborty et al., \textit{Phys. Rev.} A \textbf{79}, 061201(R) (2009); [2] M. E. Madjet et al., \textit{Phys. Rev.} A, in press. [Preview Abstract] |
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E1.00066: Predissociation and Dissociative Ionization of Rydberg States of Xe$_{2}$ and the Photodissociation of Xe$_{2}^{+}$ Stephen Pratt, Alvin Shubert, Maria Rednic The Rydberg states of Xe$_{2}$ in the region between 76,000 cm$^{-1}$ and 84,000 cm$^{-1}$ were studied by using a combination of two-photon excitation and velocity map ion imaging. The electronic states in this region are based on the Xe($^{1}$S$_{0})$ + Xe 6p and 5d dissociation limits, and the large number of states leads to numerous curve crossings and distorted potentials. These Rydberg states can decay by predissociation or fluorescence, or can be photoionized, dissociatively photoionized, or photodissociated by the absorption of a single additional photon. Furthermore, the molecular ion can be photodissociated as well. While numerous other techniques have been applied to this problem, velocity map ion imaging provides a high resolution approach to determine the operative processes. When combined with existing data obtained by other methods, the present experiments allow a more complete understanding of the assignment and behavior of these states. [Preview Abstract] |
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E1.00067: Photoionization of Xe in a Fullerene Ion Cage Ronald Phaneuf, Nagendra Aryal, David Esteves, Christopher Thomas, David Kilcoyne, Alejandro Aguilar, Carmen Cisneros Photoionization of Xe@C$_{60}^{+}$ endohedral fullerene ions was investigated in the photon energy range 76 - 170 eV by merging beams of ions and synchrotron radiation. A solid sample containing 5 ppm of Xe@C$_{60}$ was prepared by thermally evaporating and depositing C$_{60}$ onto a rotating metal cylinder that was simultaneously bombarded by a 500 eV beam of Xe$^+$ ions for several weeks. The sample was then evaporated into a low-power discharge in an ECR ion source, yielding a 30 - 40 fA beam of Xe@C$_{60}^{+}$ at 6 keV. Despite a low photoionization signal count rate of approximately 0.1 Hz, a signature due to photoexcitation of the Xe 4d giant resonance is evident in the measurements. The energy position of this feature suggests that the Xe atom donates electrons to the carbon cage of Xe@C$_{60}^{+}$. The data show no evidence for a predicted splitting of the Xe 4d giant resonance in Xe@C$_{60}$ into multiple components due to interference caused by reflection of electron waves by the carbon cage. This research was supported by the Division of Chemical Sciences, Geosciences and Biosciences of the U.S. Department of Energy. [Preview Abstract] |
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E1.00068: Energetic photoionization spectroscopy in the configuration space for atom-fullerene endohedral compounds Ruma De, Matthew McCune, Dale Hopper, Himadri Chakraborty In the photoionization of an atom confined in a fullerene the electrons directly ionized from the atom partly reflect at the cage. The delocalization of outer atomic electrons also leads to significant collateral emission from the cage site [1]. On the other hand, the atom-fullerene hybrid electrons emanate in a channel with roughly equal mix of dual character. Further, the low angular momentum fullerene electrons, that see weaker centrifugal barrier potential, emerge by a unusual ionization pathway, originating from the interior Coulomb region [2]. The interference among these amplitudes produces distinct oscillation patterns in the cross sections at energies higher than the plasmon energy region. It is shown that the transformation of a subshell cross section to the radial co-ordinates uniquely identifies the electron emission site in the compound. Results are presented for Xe@C$_{60}$.\\[4pt] [1] McCune et al., \textit{Phys. Rev.} A \textbf{80}, 011201(R) (2009)\\[0pt] [2] Hopper et al., \textit{J. Phys.} B (submitted). [Preview Abstract] |
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E1.00069: Carbon K-shell photoionization of fixed-in-space Ethylene Molecules Th. Weber, T. Osipov, M. Stener, A. Belkacem, M. Schoeffler, L. Schmidt, A. Landers, M.H. Prior, R. Doerner, C.L. Cocke Using the COLTRIMS technique we performed a kinematically complete experiment measuring photoionization of the carbon K-edge of the fixed in space ethylene molecules for photon energies (293, 302, 306, 318eV), while focusing on the symmetric break-up channel (CH2+ + CH2+). The coincidenct measurements the of reaction products along with data collection and analysis on the event-by-event basis allowed us to obtain the multi differential angular distribution of photoelectrons in the body-fixed frame of ethylene molecule. We also completed very comprehensive theoretical study of the reaction. A set of dipole transition matrix elements was calculated and extracted (7 amplitudes and 5 relative phases) from the experimental results. These matrix elements along with the complete angular distributions showed a very good qualitative agreement between the experiment and the theoretical model used. From the l = 3, m = 0 partial wave contribution to the electron angular distribution we concluded the presence of an f -wave shape resonance found around 10eV above the carbon K-edge in the ethylene molecule. [Preview Abstract] |
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E1.00070: Angular distribution of photoelectron from single-photon ionization of aligned N$_{2}$ and CO$_{2 }$molecules Cheng Jin, Anh-Thu Le, C.D. Lin We calculate the angular distribution of photoelectron from aligned N$_{2}$ and CO$_{2}$ molecules in the photoionization process. The molecules are first exposed to a pump IR laser which creates molecules that are transiently aligned or anti-aligned. These molecules are then probed by absorbing a single XUV photon (through high-order harmonic generation ) with the emission of photoelectron. We present the angular distribution of photoelectron in the laboratory frame so they can be compared to upcoming experiments. By integrating over the calculated angular distribution of photoelectron, we obtain the alignment dependence of the total ionization yield vs time delay to compare with the measurement reported by Thomann et al. [J. Phys. Chem. A \textbf{112}, 9382 (2008)]. We also study the alignment dependence of HHG for N$_{2} \quad _{ }$generated by the IR laser with the alignment dependence of single-photon ionization since the same dipole matrix elements are involved in the two processes. We further study the alignment dependence of single-photon ionization by the XUV photons vs the alignment dependence of multiphoton ionization by intense IR lasers. [Preview Abstract] |
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E1.00071: QUANTUM MEASUREMENT |
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E1.00072: Blackbody radiation shift in $^{87}$Rb frequency standard Marianna Safronova, U.I. Safronova The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature of which the leading contributor is the blackbody radiation (BBR) shift. Experimental measurements of the BBR shifts are difficult. In this work, we have calculated the blackbody radiation shift of the ground-state hyperfine microwave transition in $^{87}$Rb using the relativistic all-order method and evaluated the accuracy of our final value. Particular care is taken to accurately account for the contributions from highly-excited states. Various Rb atomic properties, including E1, E2, and E3 ground state polarizabilities, $np$ and $nd$ E1 polarizabilities, and hyperfine constants are also calculated. The results are compared with experiment and other theory where available. [Preview Abstract] |
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E1.00073: Three dimensional projection cooling Xiao Li, Karl D. Nelson, Amita B. Deb, David S. Weiss We have significantly improved the laser cooling of single atoms trapped in a 3D optical lattice with 5 \textit{$\mu $}m spacing. We use microwaves to drive lower sideband transitions between two spin states, whose spatial wavefunctions are temporarily displaced by a small lattice polarization rotation. Subsequent optical pumping completes a cooling cycle in one dimension, similar to Raman sideband cooling, but without the Raman beams [1]. We perform this cycle for each spatial direction, and repeat the process 30 times. The final vibrational excitation is below 0.2\textit{h$\nu $} in each direction, despite the Lamb-Dicke parameter being a relatively high \textit{$\eta $} = 0.37. We will also discuss our progress on performing arbitrary single qubit rotations on a target atom without affecting its neighbors. These are both important elements in the development of a site-addressable neutral atom quantum computer. \\[4pt] [1] Leonid Forster, \textit{et al} PRL 103, 233001 (2009) [Preview Abstract] |
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E1.00074: Sub-Heisenberg limited phase measurement with two-mode squeezed vacuum Gretchen M. Raterman, Petr M. Anisimov, Aravind Chiruvelli, William N. Plick, Sean D. Huver, Hwang Lee, Jonathan P. Dowling In this contribution, we present our studies of the sensitivity and resolution of phase measurement in a Mach-Zehnder interferometer with a two-mode squeezed vacuum (TMSV) input. TMSV provides a high-flux entangled state with average photon number of $\bar {n}$. Parity detection is suggested as a possible detection scheme, which can be carried out, for example, by using the NIST photon number resolving detectors. We show that super-resolution and ``sub-Heisenberg'' sensitivity is obtained with TMSV and parity detection. In particular, in our setup, the signal as a function of the phase evolves $\bar {n}$ times faster than in traditional schemes, and the uncertainty in the phase estimation is better than $1 \mathord{\left/ {\vphantom {1 {\bar {n}}}} \right. \kern-\nulldelimiterspace} {\bar {n}}$. [Preview Abstract] |
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E1.00075: Experimentally measurable non-monotonicity for the quantum-classical transition in nonlinear nanoelectromechanical systems (NEMS) Qi Li, Adam Steege, Arie Kapulkin, Arjendu Pattanayak Current experiments are exploring the quantum-classical boundary in nonlinear oscillator systems, that is, exploring the effects of changing size and changing decoherence. One such nonlinear system, the driven damped Duffing oscillator had been previously shown to display non-monotonic behavior in phase space. In this paper, we show how this behavior can be mapped to measurable quantities in experiments. These quantities show that the quantum-classical transition is nonmonotonic in the effective size of $\hbar$. Such a system is within experimental reach possibly for atomic systems and definitely for nanoelectromechanical systems (NEMS). [Preview Abstract] |
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E1.00076: Implementation of weak measurement for single nuclear spin qubit by using cavity enhanced Faraday rotation Atsushi Noguchi, Yujiro Eto, Nobuyuki Takei, Makoto Takeuchi, Peng Zhang, Masahito Ueda, Mikio Kozuma When an off-resonant light field is coupled with atomic spin, its polarization can rotate depending on the direction of the spin via a Faraday rotation. Because the Faraday rotation deterministically entangles atomic spin states with photonic polarization states the information of the spin can be obtained by performing projective measurement on the ancillary photon. Employing the proper measurement basis, not only projective but also weak measurement can be implemented for the spin state. Here we report the observation of Faraday rotation by an angle of more than 10$^{\circ}$ for a single 1/2 nuclear spin of the 171Yb atom. Nuclear spin is the promising candidate of the quantum bit because of the long coherence time due to its extremely small magnetic moment. In our experiment, Faraday rotation was enhanced by using a high-finesse($\sim $100,000) optical micro-cavity. We also measured variation of the spin state after single photon counting of the transmitted weak probe pulse. The spin state was either projected or weakly measured. [Preview Abstract] |
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E1.00077: Ultra Smooth Microfabricated Mirrors for Atom Chip Based Cavity QED Thomas Loyd, Francisco Benito, Grant Biedermann, Kevin Fortier, Daniel Stick, Peter Schwindt, Matthew Blain Microfabricated optical cavities are an attractive system for atomic physics research. When paired with an atom the small mode volume can lead to strong atom-cavity coupling with only a modest finesse. Such systems are of significant interest for applications in quantum information [1]. While experiments using a single cavity or a small number of cavities tend to be tractable, scaling the number of cavities required for a useful quantum network remains challenging [2]. In this work, we have developed an ultra high reflectivity micro-mirror for scalable quantum information systems taking the work of Trupke et al. [3] as a starting point. We have demonstrated that our micro-mirror fabrication technique produces ultra smooth mirror surfaces of 2.2 Angstroms rms. Optical cavities formed with these mirrors exhibit a high finesse of over 60,000 leading to a calculated single atom cooperativity of more than 200. These cavities are attractive candidates for integrated cavity QED experiments and quantum information processing on an atom chip platform. [1]. P K. Vahala, ed., \textit{Optical Microcavities}, (World Scientific, Singapore, 2004). [2]. H. J. Kimble, \textit{Nature}, \textbf{453}, 1023 (2008). [3]. M. Trupke, E. A. Hinds, S. Eriksson, E. A. Curtis, Z. Moktadir, E. Kukharenka, and M. Kraft, \textit{Appl. Phys. Lett.}, \textbf{87}, 211106 (2005). [Preview Abstract] |
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E1.00078: Lossless qubit state detection of single neutral atoms Martin M\"ucke, Joerg Bochmann, Christoph Guhl, Stephan Ritter, David L. Moehring, Gerhard Rempe Trapped neutral atoms are among the most promising resources for quantum information science. In a single trapped atom, the quantum bit (qubit) is typically encoded in or mapped onto atomic hyperfine states. However, hyperfine qubit read-out has proven remarkably difficult for neutral atoms. Existing protocols do not obtain an answer in every read-out attempt or suffer from loss of the atom during detection. We introduce a state detection scheme based on cavity-enhanced fluorescence. It makes use of the Purcell effect to establish a controlled coupling between qubit and environment. In an experiment with a single trapped Rubidium atom, we achieve a hyperfine state detection fidelity of 99.4\,\% in 85$\,\mu$s while a result is obtained in every read-out attempt. Most important, the qubit can be interrogated many hundred times without loss of the atom. This presents an essential advancement for the speed and scalability of quantum information protocols based on neutral atoms. Our scheme can be generalized to all systems in which the qubit is optically accessible. [Preview Abstract] |
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E1.00079: Multi-pass cells for quantum non-demolition Faraday rotation measurements in Rb vapor Pranjal Vachaspati, Michael Romalis Quantum non-demolition spin measurements using paramagnetic Faraday rotation benefit from a large optical depth. Optical cavities have traditionally been used for increasing the rotation signal. However, optical cavities have a small mode volume and are very sensitive to alignment and laser frequency. We explore the use of multi-pass cavities using cylindrical mirrors with a hole for the entrance and exit of the laser beam. Such cavities are much less sensitive to mirror quality and alignment and do not require laser frequency locking or power coupling matching. We have developed analytical models for Gaussian beam propagation in such cavities to optimize the uniformity of cell illumination. Experimentally, beam patterns with 38 and 70 passes have been realized. We have also fabricated Rb cells with high quality anti-reflection windows and performed optical absorption and polarization rotation measurements with 38 passes through the cell. Latest progress toward measurements of quantum spin fluctuations in this arrangement will be reported. [Preview Abstract] |
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E1.00080: Heisenberg Limited Two Species Ion Clock Garry Goldstein, Paola Cappellaro, Liang Jiang, Anders Sorensen, Mikhail Lukin Motivated by recent experiments [1, 2] we propose a new method that attains nearly Heisenberg limited precision clock measurement, exploiting new techniques for environment assisted metrology [3]. Our method makes use of two species of trapped ions in a linear Paul trap, a logic ion for coherent control and readout and multiple spectroscopy ions with stable clock transitions, to achieve Heisnberg limited sensing. It does not require individual addressability of the spectroscopy ions and uses only multi-chromatic (Sorensen-Molmer) gates for entangling operations between the ions, as opposed to the Cirac-Zoller gates used so far. This allows one to use multiple spectroscopy ions in a single Paul trap, improving on previous methods that could use only one ion at a time. Furthermore we find that many of the sources of noise that act as decoherence in regular multi-chromatic gates do not effect the sensitivity of the proposed metrology method. \\[4pt] [1] T. Rosenband et al., Science 319, 1808 (2008)\\[0pt] [2] P. O. Schmidt et al., Science 309, 749 (2005)\\[0pt] [3] G. Goldstein et al., Arxiv 1001.0089 [Preview Abstract] |
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E1.00081: Non-uniform position measurements Jonathan Mackrory, Kurt Jacobs, Daniel Steck We present a generalization of the standard treatment of continuous position measurements. In our formulation the measurement strength can vary in space, as would be the case in any physical realization of a continuous position measurement. We start from the Positive Operator Valued Measure that realizes a generalized position measurement, and use that to construct quantum trajectories for an atom's motion. This measurement could be experimentally realized by coupling an atom to an optical field and monitoring the scattered radiation. In particular, we consider the case of a free particle incident on a measurement function. The results of our numerical simulations are presented, with a focus on the case of a step measurement function. In general, the particle can either reflect off the measurement, or be detected and transmit past the step. We find that for large measurement strengths there is a high probability for the particle to reflect coherently off of the measurement, an effect analogous to the quantum Zeno effect. [Preview Abstract] |
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E1.00082: Spin Dependent Forces and Entanglement of Atomic Qubits using Optical Frequency Combs D. Hucul, D. Hayes, D.N. Matsukevich, P. Maunz, S. Olmschenk, Q. Quraishi, W. Campbell, J. Mizrahi, C. Senko, C. Monroe The spectral purity and large bandwidth of pulsed lasers makes them attractive candidates for precision control of multi-level atomic systems. We use a train of off resonant picosecond pulses from a mode-locked laser to drive stimulated Raman transitions between the hyperfine levels ($\sim$10 GHz spacing) of trapped ytterbium ions and to cool to the quantum ground state of motion. By simultaneously addressing the spin and the motion of trapped ions using a train of laser pulses, we apply spin-dependent forces to create a single-ion Schrodinger cat state and implement a gate between two trapped ions to entangle their spins [1]. We also use high-intensity pulses to demonstrate fast ($<$10 ps) single qubit operations that can be used as the building blocks for fast multi-qubit entangling gates [2]. [1]. D. Hayes et al. arXiv:1001.2127v2 [2] Garc\'{i}a-Ripoll \textit{et al.}, PRL \textbf{91}, 157901 (2003). Duan, PRL \textbf{93}, 100502 (2004). [Preview Abstract] |
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E1.00083: Entangling the lattice clock: Towards Heisenberg-limited timekeeping Jonathan D. Weinstein, Kyle Beloy, Andrei Derevianko We present a scheme for entangling the atoms of an optical lattice to reduce the quantum projection noise of a clock measurement. The divalent clock atoms are held in a lattice at a ``magic'' wavelength that does not perturb the clock frequency -- to maintain clock accuracy -- while an open-shell $J=1/2$ ``head'' atom is coherently transported between lattice sites via the lattice polarization. This polarization- dependent ``Archimedes' screw'' transport at magic wavelength takes advantage of the vanishing vector polarizability of the scalar, $J=0$, clock states of bosonic isotopes of divalent atoms. The on-site interactions between the clock atoms and the head atom are used to engineer entanglement and for clock readout. [Preview Abstract] |
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E1.00084: Ensemble Quantum Control of Neutral Atoms Qudits Brian Mischuck, Seth Merkel, Ivan Deutsch, Poul Jessen Atomic spins are robust and highly controllable, making them an excellent platform for quantum information processing. In addition, the large number of magnetic substates in the electronic ground state of heavy alkali atoms makes them natural candidates for encoding qudits. In previous work we showed that the complete hyperfine manifold is controllable through the application of oscillating radio and microwave frequency magnetic fields. In the present work we show how such control waveforms can be designed to be robust to inhomogeneities such as spatio-temporal variations of the fields. Borrowing on ideas originally developed for NMR, we show how to drive an inhomogeneous ensemble of Cs-133 atoms through a given desired evolution. By appropriate choice of rf power and phase, we can limit the dynamics to remain in the lower hyperfine manifold (F=3) plus an additional auxiliary state in the upper manifold, an 8 dimensional Hilbert space that is controllable. By brute force optimization, we find waveforms that act for a time of 500 $\mu $s and will achieve an average fidelity of greater than 0.99 for a 5{\%} variation in all of the parameters . We also show how to synthesize different states in different spatial regions by using a spatially varying magnetic field. [Preview Abstract] |
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E1.00085: Phase measurement with two-mode squeezed vacuum in the presence of loss Petr M. Anisimov, Jonathan P. Dowling A two-mode squeezed vacuum (TMSV) provides a high-flux entangled state with an average photon number of $\bar {n}$. Thus it is an attractive candidate for phase estimations with a suggested detection scheme being based on measuring the parity of a state of light. This can be carried out, for example, by using the NIST photon number resolving detectors. In this contribution, we present our studies of the sensitivity and resolution of such a phase measurement scheme in the presence of loss. We do this in terms of the Wigner function, which has a significantly simplified description of losses. We show that a discussed phase measurement scheme remains super-sensitive and super-resolving for a certain amount of loss. [Preview Abstract] |
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E1.00086: Signal-to-noise ratio of quantum imaging using entangled photon-number state Sai Vinjanampathy, Jeff Adams, Barbara Capron, Claudio Parazzoli, Jonathan Dowling Quantum Imaging involving a source with N+1 photons has been of interest in the recent years. N of these photons are present in the arm where the object is placed and are entangled with 1 photon in the other arm. The image is recorded in coincidence. We present here some ideas on how to generate such photons in the lab and study the signal-to-noise ratio for such an imaging scheme. Some preliminary experimental results are also presented. [Preview Abstract] |
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E1.00087: Testing Quantum Randomness in Single-Photon Polarization Measurements David Branning, Matthew Bermudez A binary sequence constructed from 17 million polarization measurements of single photons was subjected to a comprehensive set of tests for randomness. The polarization measurements were carried out using photon pairs from spontaneous parametric downconversion under low-intensity conditions similar to those of many optical quantum cryptography protocols. One member of each photon pair was used as a detection trigger, while the other was put into a superposition state of horizontal (H) and vertical (V) polarization, and then measured in the H-V basis. The resulting sequence of binary outcomes was subjected to a suite of fifteen tests developed at the National Institute of Standards and Technology (NIST) to assess the quality of algorithmic random-number generators. Several of these tests require many distinct sub-sequences of at least 1 million bits, with very low bias, in order to be meaningful. In this experiment the low bias of the collected sequence (0.04{\%}) enabled all of the NIST tests to be applied directly to the polarization measurements themselves, without the use of numerical unbiasing procedures. [Preview Abstract] |
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E1.00088: Far-field optical imaging and manipulation of individual spins with nanoscale resolution Peter Maurer, Jero Maze, Paul Stanwix, Liang Jiang, Alexey Gorskov, Alexander A. Zibrov, Benjamin Harke, Jonathan Hodges, Alexander S. Zibrov, Daniel Twitchen, Stefan Hell, Ronald Walsworth, Mikhail Lukin A fundamental limit to existing optical far field techniques for measurement and manipulation of spin degrees of freedom is set by diffraction. Here, we demonstrate an efficient far-field optical technique that overcomes this limit. Our technique involves selective flipping of the orientation of individual spins, associated with Nitrogen-Vacancy centers in diamond, using a focused beam of light with intensity vanishing at a controllable location. This enables simultaneous single-spin imaging and magnetometry at the nanoscale. Furthermore, by inhibiting spin transitions away from the laser intensity null using a quantum Zeno-like effect, selective coherent rotation of individual spins is realized. This technique can be extended to sub-nanometer dimensions, thus enabling applications in diverse areas ranging from quantum information science to bioimaging. [Preview Abstract] |
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E1.00089: MANY-BODY PHYSICS WITH ULTRA-COLD ATOMS: EXPERIMENT AND SIMULATIONS |
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E1.00090: A simple and versatile system for simulating non-abelian gauge fields Daniel Braun We consider a single, harmonically trapped atom with internal hyperfine structure in an external magnetic field. We show that by a simple canonical transformation the system can be mapped to a charged particle moving in an abelian or non-abelian gauge potential. The form of the gauge potential can be rather freely chosen by suitably adjusting gradients of the magnetic field components. We demonstrate in particular how Rashba or Linear-Dresselhaus couplings can be implemented, and how {\em Zitterbewegung} of a Dirac particle can be simulated. We study the {\em Zitterbewegung} in some detail and show that the 2D harmonic confinement potential prevents the {\em Zitterbewegung} from decohering, thus allowing its observation on long time scales. [Preview Abstract] |
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E1.00091: Rearranging the Exponential Wall for Large N-Body Systems Martin Dunn, Deborah Watson The general quantum mechanical $N$-body problem is widely believed to be $NP$ complete, a complexity class for which no polynomial time algorithm has been found. The resources required for an exact solution are thought to scale exponentially with $N$, doubling for every particle added. With current numerical resources, this problem ``hits a wall'' around $N=10$ (within a factor of 2). We have formulated a perturbation method for bosons which uses symmetry to rearrange this exponential wall by shifting the work from numerical effort for a single $N$ to analytic work valid for all $N$. This series is invariant under the $N!$ operations of the symmetric group $S_N$, allowing group theory and graphical techniques to be used to solve the problem exactly and analytically at each order for an arbitrary interaction and for arbitrary $N$, i.e. the problem scales as $N^0$ at each order. The current work investigates the growth of complexity as a function of order by enumerating the graphs that correspond to the basis tensors at each order. The exponential complexity reappears in an exponential wall that scales with the order of the series. Thus, exact analytical calculations are possible for very large systems through low order. [Preview Abstract] |
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E1.00092: Simulating Thermopower in Mott-Hubbard Materials Stanimir Kondov, William McGehee, Joshua Zirbel, Brian DeMarco We report progress on a new project to simulate and understand thermopower in Mott-Hubbard materials. Potassium-40 atoms that have been cooled to degeneracy and loaded into an optical lattice serve as the physical analog to these poorly understood, highly-correlated systems. A temperature gradient across the atomic cloud will induce mass flow, which can be directly related to an equivalent thermopower of charged particles. The transport properties of the cloud, which will vary with the dimensionality and strength of the lattice, will be measured using time-of-flight imaging and employed to determine the impact of Hubbard parameters, disorder, and lattice geometry on thermopower. [Preview Abstract] |
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E1.00093: Quantum criticality in cold atoms Kaden Hazzard, Erich Mueller We construct a general set of techniques to extract universal quantum critical behavior from cold atoms experiments. Quantum criticality --- the finite temperature behavior of systems near quantum phase transitions --- is a cornerstone of modern solid state physics, providing examples of non-quasiparticle excitations and interpretations of a wide variety of strongly correlated materials. Since often even the simplest models' behavior is unknown, cold atoms can dramatically improve our understanding. Yet the phenomenology of the quantum critical regime has received little attention, despite the fact that many ongoing experiments are in this regime. We show that quantum critical phenomena are robust in cold atoms: they persist despite the small number of atoms and the inhomogeneity of the harmonic traps. We construct novel analysis methods to observe quantum criticality in these system. We demonstrate the utility of these methods by examining exactly solvable models and quantum Monte Carlo calculations. Additionally, we make first comparisons with experiments. We show that ongoing experiments can immediately impact deep open questions regarding the so-called ``O(2) rotor model'' at finite chemical potential, and the fermionic Mott insulator/metal crossover. [Preview Abstract] |
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E1.00094: The Dicke Quantum Phase Transition in a Superfluid Gas Coupled to an Optical Cavity Christine Guerlin, Kristian Baumann, Ferdinand Brennecke, Tilman Esslinger A fundamental approach to collective matter-light interaction is given by the Dicke model which has been predicted to show an intriguing quantum phase transition. We have realized the Dicke quantum phase transition in an open system formed by a Bose-Einstein condensate coupled to an optical cavity, and observed the emergence of a self-organized supersolid phase [1]. The phase transition is driven by infinitely long-ranged interactions between the condensed atoms. We show that the phase transition is described by the Dicke Hamiltonian, including counter-rotating coupling terms, and that the supersolid phase is associated with a spontaneously broken spatial symmetry. The boundary of the phase transition is mapped out in quantitative agreement with the Dicke model. \\[4pt] [1] K. Baumann, C. Guerlin, F. Brennecke, T. Esslinger, arXiv 0912.2361, 2009 [Preview Abstract] |
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E1.00095: Spatially resolved compressibility measurements in the disordered Bose-Hubbard model Matthew Pasienski, Carolyn Meldgin, Brian DeMarco Direct comparison between our recent disordered optical lattice measurements and theoretical predictions for the disordered Bose-Hubbard model have been complicated by the inhomogeneous density profile of the trapped gas. We propose to study a narrow range of densities by exclusively imaging atoms at the center of the trap. To achieve this, microwave-frequency magnetic fields will be used to transfer atoms into a hyperfine state that is selectively imaged. Spatial discrimination will be realized using hyperfine-state-sensitive AC Stark shifts induced by crossed laser beams. We will couple this imaging technique with transport and compressibility measurements to directly determine the disordered Bose-Hubbard phase diagram. [Preview Abstract] |
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E1.00096: Antiferomagnetic transition of trapped fermions in a two-dimensional optical lattice Kensuke Inaba, Makoto Yamashita We study the finite temperature properties of two-component fermionic atoms trapped in a two-dimensional (2D) optical lattice. We apply the self-energy functional approach to the 2D Hubbard model with a harmonic trapping potential. This powerful approach allows us to investigate both antiferromagnetic (AF) and Mott transitions in this system. We first evaluate experimentally observed quantities such as a renormalized cloud size and a fraction of atoms on doubly occupied sites. The results show the reasonable agreement with the recent experimental observations. We further investigate thermodynamic quantities of entropy and grand potential which are sensitive to the transitions. We find that these quantities provide evidence of a crossover between the Mott insulating and metallic phases at certain temperatures. In addition, at lower temperature, we find that entropy exhibits a cusp-like anomaly, suggesting a second or higher order AF transition. We estimate the AF transition temperatures and clarify how the trapping potential affects this magnetic transition. [Preview Abstract] |
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E1.00097: Probing Interaction-Induced Ferromagnetism in Optical Superlattices Javier von Stecher, Eugene Demler, Mikahil Lukin , Ana Maria Rey We analyze how to use ultracold fermionic atoms loaded in optical superlattices for a controllable preparation and detection of interaction-induced ferromagnetism. First, we discuss how to experimentally achieve Nagaoka ferromagnetism in an array of isolated plaquettes (four lattice sites arranged in a square). Next, we allow for weak interplaquette tunneling and analyze the occurrence of itinerant ferromagnetism. Since ferromagnetism is unstable in the presence of weak interplaquette couplings, we propose to mediate long-range ferromagnetic correlations via double-exchange processes by exciting atoms to an excited vibrational band. We calculate the phase diagram of the two-band plaquette array and discuss conditions for the stability and robustness of the ferromagnetic phases in this system. Experimental implementations of the proposed schemes are discussed. [Preview Abstract] |
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E1.00098: Experimental Probe of Antiferromagnetic Ordering in a 3D Optical Lattice of $^6$Li James M. Hitchcock, P.M. Duarte, T.A. Corcovilos, R.G. Hulet We have developed an apparatus to probe magnetic ordering in $^6$Li using a two spin mixture of magnetic sub-levels from the lowest hyperfine state. The degenerate Fermi gas is prepared all optically by loading and evaporative cooling in a high-power far-red detuned optical trap. Our primary goal is the observation of the antiferromagnetic (AFM) N\'{e}el phase predicted at very low temperatures for an equal spin mixture in a three dimensional lattice with one fermion per site. We present our progress toward the identification of the AFM phase and the investigation of the Fermi-Hubbard model in this system. We also discuss methods used to distinguish spatial and magnetic ordering within a simple cubic lattice. Specifically, we intend to identify the AFM phase using near resonant Bragg scattering from the (${\scriptstyle{^1\!/_2}\,{^1\!/_2}\,{^1\!/_2}}$) lattice plane. [Preview Abstract] |
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E1.00099: Exact Parent Hamiltonians for the Fractional Quantum Hall State in an Optical Lattice Eliot Kapit, Erich Mueller We construct lattice Hamiltonians for which the $\nu = 1/m$ Laughlin state is an exact eigenstate. These Hamiltonians (both bosonic and fermionic versions) contain longer-range hopping terms, but the only interparticle interaction is a hard-core repulsion. Under many circumstances, these Hamiltonians are well approximated by ones with only nearest and next-nearest neighbor hoppings, and could be realized with ultracold atoms. Beyond this, we argue that variations of these fractional quantum Hall states can be observed near the Mott Lobes in a rotating optical lattice when the density of excess particles or holes is commensurate with the magnetic flux. We discuss the detection of these states. [Preview Abstract] |
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E1.00100: Probing quasi-2D condensates in an 1D optical lattice Shihkuang Tung, Giacomo Lamporesi, Daniel Lobser, Lin Xia, Eric Cornell Quasi-2D condensate slices are created by loading a 3D Bose-Einstein condensate into a 1D optical lattice. A microwave pumping scheme is then applied to select one slice for imaging. In our experiment, we use in-trap and time-of-flight imaging techniques to probe a quasi-2d Bose gas. The results from the two different imaging techniques help determine more accurately the nature of an interacting Bose gas in a harmonically trapped system. [Preview Abstract] |
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E1.00101: Ground State Properties of Cold Bosonic Atoms At Large Scattering Lengths Junliang Song, Fei Zhou We study bosonic atoms at large scattering lengths using a variational method where the condensate amplitude is a variational parameter. We further examine momentum distribution functions, chemical potentials, the speed of sound, and spatial density profiles of cold bosonic atoms in a trap in this limit. The later two properties turn out to bear similarities of those of Fermi gases. The estimates obtained here are applicable near Feshbach resonances, particularly when the fraction of atoms forming three-body structures is small and can be tested in future cold atom experiments. [Preview Abstract] |
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E1.00102: LASER COOLING AND TRAPPING |
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E1.00103: Continuous, guided atomic beams Mallory Traxler, Erik Power, Georg Raithel We report on progress towards a continuous atom laser based on continuous evaporative cooling in a magnetic guide. In the pursued approach, atoms are collected in a MOT located on the guide axis, transferred into a three-dimensional magnetic trap, and adiabatically merged, using a short magnetic conveyor, with a cold-atom flow in the evaporative-cooling portion of the guide. To enable continuous guiding and cooling, the guiding field is always on. The majority of the work in assembling this apparatus is concluded. The apparatus shares some of its characteristics with an operational guide, in which $^{87}$Rb atoms are guided over a distance of 1.5 m with a transverse temperature of 400 $\mu $K, a longitudinal temperature of 1 mK, and a flux of 3x10$^{7}$ atoms/s. The operational setup has recently been employed to explore the prospects of a photo-ionization / ion counting scheme for efficient atom detection in magnetic atom guides. Further, we have prepared Rydberg atoms in the guide and studied the guiding as well as the Penning ionization dynamics of these atoms. The current status of both the Rydberg guiding experiments and the continuous evaporative cooling apparatus will be presented. [Preview Abstract] |
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E1.00104: Progress toward high bandwidth cold atom source Matthew Squires, James Stickney, Paul Baker, Evan Carlson, Stefan Fagan-Kelly, Steven Miller Confined cold and ultra-cold atomic devices have operated at bandwidths of significantly less than 1 Hz, because the laser cooling stage and the trapping stage typically occur in the same experimental region. The low bandwidth is a current limitation of cold atom devices (e.g. interferometers). One option for a high bandwidth source of cold atoms is concurrent laser cooling in one chamber and magnetic trapping in a second chamber so the magnetic trap can be continuously maintained. This dual chamber source of atoms will at least require: optical isolation, a method for transporting between the chambers, merging new atoms with existing atoms, and providing a stable trap during all of the cooling and transport operations. We present the simulation and results of transporting atoms with high efficiency, the optimization of magnetic trapping fields, and the transfer of atoms to an atom chip for cold atom interferometry. [Preview Abstract] |
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E1.00105: The collimation of intense atomic beams by parallel tube-arrays John Huckans We report on a series of experiments to characterize the collimation of atomic vapor beams. Hot $^{6}$Li atoms were emitted from an atomic beam source and collimated by various tube-array sections. Flux intensity profiles were obtained with several arrays for tubes having a range of shape factors, $\gamma $ = d/L. Measurements were made in the molecular and hydrodynamic flow regimes (i.e. for different Knudsen parameters). [Preview Abstract] |
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E1.00106: Bichromatic force slowing of He* for ultracold atom production M.A. Chieda, E.E. Eyler Magneto-optical traps (MOTs) for metastable helium are particularly difficult to load, usually requiring Zeeman slowers with a length of 2-3 meters and a high degree of engineering complexity. The bichromatic force offers an alternative approach to deceleration of a He* beam that should allow a significantly simpler and much more compact apparatus. Based on controlled phasing of absorption and stimulated emission from a pair of counterpropagating beams, it can be orders of magnitude stronger than the radiative force. Slowing of He* by as much as $\Delta v = 325$~m/s has been previously demonstrated, but in order to bring atoms to near-rest, the technique must be extended to $\Delta v \approx 900$~m/s. We are conducting computer modeling and experimental studies of two approaches to this challenge. The first is a two-stage slower, each with a bichromatic detuning of about $\pm 375$~MHz from the appropriate center velocity. The second is a frequency-chirped single-stage slower in which the frequencies of a pair of lasers are swept to compensate the Doppler shift of the decelerating atoms. [Preview Abstract] |
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E1.00107: Measurements of light shifts in cold atoms using Raman pump-probe spectroscopy Samir Bali, Nathan Souther, Richard Wagner, Peter Harnish, Matthew Briel We have measured light shifts, also known as AC Stark shifts, as a function of laser intensity in cold Rubidium atoms by observing sub-natural linewidth gain and loss features in the transmission spectrum of a weak probe beam passing through the atomic sample. The observed energy-level shifts for atoms in a magneto-optical trap (MOT) are found to be consistently higher than that obtained in optical molasses (i.e., when the magnetic field gradient in the MOT is turned off) . Using a simple model of a multilevel Rubidium atom interacting with pump and probe beams, we have calculated the theoretical light shift as a function of intensity. A comparison of these calculated values with the light shift data obtained for molasses reveals good agreement between experiment and theory. Further, our model elucidates the role of the Zeeman shifts arising from the magnetic field gradient in the observed probe transmission spectrum for the MOT. [Preview Abstract] |
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E1.00108: 100-fold improvement on Atom Trap Trace Analysis for radiokrypton dating W. Jiang, W. Williams, Y.R. Sun, K. Bailey, A.M. Davis, S.-M. Hu, Z.-T. Lu, P. Mueller, T.P. O'Connor, R. Purtschert, N.C. Sturchio Atom Trap Trace Analysis (ATTA) has been used to analyze the rare isotope Kr-81 (half-life = 230 kyrs, I.A.$\sim $ 10$^{-13})$ in environmental samples. Kr-81 analysis can now be used to determine the ages of groundwater samples in the range of 50 -- 1,000 kyrs. The previous instrument (ATTA-2) had an overall counting efficiency of 0.01{\%} and, required a water sample of 1,000 liters. We are developing a new instrument (ATTA-3) to laser-trap and count Kr-81 atoms with the goal of reaching a counting efficiency of 1{\%}, which would reduce the sample size to less than 100 liters of water or ice. Recently we have demonstrated a counting rate of $\sim $ 2000 $^{81}$Kr atoms/hr, which represents a 100-fold improvement over ATTA-2. ATTA-3 will enable a wide range of applications in the earth sciences. [Preview Abstract] |
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E1.00109: Development of an Atom Counting System to Measure Ultralow $^{85}$Kr Contamination in Liquid Xenon Dark Matter Detectors Tanya Zelevinsky, Claire Allred, Luke Goetzke, Elena Aprile Weakly Interacting Massive Particles (WIMPs) may constitute the dark matter that makes up 25\% of our universe. Various WIMP detection methods are currently pursued; the XENON experiment expects to detect low energy nuclear recoils in liquid xenon due to dark matter interactions. An experiment with a ton scale Xe target is projected to be sensitive to a spin-independent WIMP-nucleon collision cross section of 10$^{-47}$ cm$^2$. To achieve this high sensitivity, background events from inherent radioactivity of the target must be suppressed, particularly the beta-decay of the $^{85}$Kr rare isotope. The tolerable contamination by all Kr isotopes is below a part per trillion. To quantitatively measure the Kr contamination of Xe, we are constructing a single atom counting apparatus that relies on laser cooling and trapping of metastable Kr. The detection of ultralow atom numbers is made possible by the excellent spatial selectivity of the magneto-optical trap and efficient fluorescence collection on the strong cycling transition of Kr. [Preview Abstract] |
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E1.00110: Microwave and RF potentials for atom trapping and precision interferometry Jim Field, Austin Ziltz, Megan Ivory, Seth Aubin We present plans and progress towards the development of microwave and RF (u/RF) potentials using atom chip technology for interferometry and novel trapping of ultracold potassium atoms. These potentials are inherently conservative, spin-dependent, and allow tunable atom-atom interactions via magnetic Feshbach resonances. They can be used for interferometry of trapped ultracold thermal and quantum gases, atomtronic and quantum pumping ``circuits,'' and sympathetic-adiabatic cooling. We give theoretical overviews of u/RF potentials and interferometers with specific application to Casimir-Polder force measurements. The small hyperfine splitting of potassium isotopes simplifies the engineering of u/RF potentials, while also providing bosonic and fermionic species. We focus on the use of fermion isotopes for high accuracy interferometric and atomic clock applications. [Preview Abstract] |
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E1.00111: Bichromatic Cooling used to Achieve a Large Number of Cold Atoms in a Compact Volume Tara Cubel Liebisch, Elizabeth Donley, Eric Blanshan, John Kitching For cold atomic samples to be used in emerging technologies such as compact atomic clocks and sensors it is necessary to achieve small sample sizes with a large number of cold atoms. This is a challenge because in a magneto-optical trap (MOT) the number of cooled and trapped atoms scales as d$^{4}$, where d is the diameter of the laser beams (Gibble et.al.OL\textbf{17}, 526 (1992)). In a MOT the maximum radiation force is limited by spontaneous emission to hk$\gamma $/2. Bichromatic cooling first studied by S\"{o}ding et.al. (PRL\textbf{78},1420(1997)), takes advantage of stimulated emission and driven Rabi oscillations to cool atoms over a broad velocity range with forces $>>$ hk$\gamma $/2. With the faster cooling rates, larger atom numbers can be obtained in very small cooling volumes. We report on preliminary results of cooling a thermal beam down to MOT capture velocities over distances of $<$1cm, our experimental set up, and theoretical results using our experimental parameters. We expect to be able to load a MOT with 1mm diameter beams with a factor of 100 more atoms than if loaded from a background vapor. With this atom sample we estimate we could achieve a clock stability of 1E-12 @ 1s with a Ramsey time of 4ms, a cycle time of 10ms, and a clock transition frequency of 6.8GHz. \\[0pt] We would like to acknowledge funding from NIST, DARPA, and NRC. [Preview Abstract] |
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E1.00112: Design of a Permanent Magnet Zeeman Slower Sean Krzyzewski, Thomas Akin, Parshuram Dahal, Eric Abraham We present a new design for a permanent magnet Zeeman slower for loading magneto-optical traps in laser cooling experiments. In addition to eliminating the need for a power source, the simple design facilitates vacuum chamber baking and construction. We compare experimental results with numerical simulations. [Preview Abstract] |
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E1.00113: Variation of optical sideband intensity with current tuning in an extended cavity diode laser Timothy Roach, Josh Ryor We have observed large, systematic changes in the intensity of optical sidebands of an extended cavity diode laser (ECDL) as the DC injection current is changed. These sidebands have applications for Raman spectroscopy and optical pumping (in our case, repumping of a laser cooling transition). The sidebands are produced by microwave modulation of the injection current ($f \quad \sim $ 3GHz) and the optical intensity is about 2{\%} of the total. Changing the DC current of the grating feedback ECDL produces optical frequency tuning in smooth stretches separated by mode hops several mA apart. Within each smooth-tuning cycle the intensity of the sidebands changes by a factor of 5 or more. We compare this behavior to a model of the competition between the laser chip and ECDL cavity modes. [Preview Abstract] |
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E1.00114: Measurement of cold atoms' distribution in a closed system Liang Liu, Xu-Cheng Wang, Hua-Dong Cheng, Yan-Ling Meng, Ben-Cang Zheng, Yu-Zhu Wang In this paper, we present an experiment to measure the spatial distribution of cold atoms in a ceramic cell. The cold atoms are first cooled by diffuse light produced by multiple scattering of laser light by inner surface of the cell. An inhomogeneous magnetic field is applied after the atoms are cooled by using a pair of anti-Helmholtz coils, and thus the shift of atomic magnetic sub-levels is position-dependent. We move the anti-Helmholtz coil horizontally while keeping the probe laser beam resonant with the cold atoms at the zero magnetic field. The absorption of the probe beam gives the number of cold atoms at different position. The results show that at the center of the cell, less atoms exist due to the leakage of diffuse light into the hole connecting to the vacuum pump. The method we developed in this paper is useful to detect cold atoms in a region where imaging is not possible. [Preview Abstract] |
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E1.00115: Analytic calculation of the transient radiation force on a two-level atom Heung-Ryoul Noh, Min Jeong Seo, Sun Hye Kang We present an analytic calculation of the transient radiation force on a two-level atom interacting with a single mode laser- field. The analytic form of the radiation forces is derived by solving the optical Bloch equations analytically. It is confirmed, in particular, that the radiation force consists of reactive as well as dissipative components, whose explicit analytic forms of the transient solutions can be explicitly obtained. The succinct analytic solutions of the radiation forces may be helpful for a convenient and intuitive description of the complex atomic dynamics such as interaction with various laser fields. [Preview Abstract] |
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E1.00116: Using Atom Trap Trace Analysis for Radioactive Krypton Background Analysis Benjamin Miles, Chad Orzel We will measure very accurately the concentration of krypton in a mixture of noble gases by using the Atom Trap Trace Analysis (ATTA) method to trap and count single krypton atoms. Such measurements are critical for the new generation of neutrino and dark matter detectors that use liquid noble gases (xenon or neon) as a scintillation medium. Beta decay of the rare isotope $^{85}$Kr is a significant source of background counts in such detectors, which can tolerate krypton contamination only at the $10^{-15}$ level. We estimate that the ATTA method can detect Kr/Rg levels as low as $3\times10^{-14}$ in just 3 hours, considerably faster than more conventional techniques. We will discuss recent progress toward the use of ATTA to measure krypton contamination in neon or xenon. [Preview Abstract] |
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E1.00117: Dynamic dipole polarizabilities of alkali dimers Olivier Dulieu, Romain V\'exiau, Mireille Aymar, Nadia Bouloufa Experiments aiming at trapping ultracold molecules and at manipulating their internal quantum state rely on their interaction with far-detuned laser fields. Using accurate potential energy curves and transition dipole moments from advanced quantum chemistry computations [1], we calculate the dynamic dipole polarizability of homonuclear and heteronuclear alkali dimers via a summation over a large number of excited electronic states. We identified ranges of ``magic'' wavelengths where the ac Stark shift for the dimer in its lowest vibrational level of the ground state is the same than for a pair of non-interacting atoms. We use the same formalism to evaluate dipole polarizabilities at imaginary frequencies which are relevant for computing long range interactions between atoms and molecules [2]. \\[4pt] [1] M. Aymar and O. Dulieu, Mol. Phys. \underline{105}, 1733 (2007)\\[0pt] [2] A. Derevianko , S. G. Porsev, and J. F. Babb, arXiv:0902.3929v1 [physics.atom-ph] 23 Feb 2009 [Preview Abstract] |
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E1.00118: Novel cooling schemes for atomic strontium Benjamin Bloom, Sebastian Blatt, Travis Nicholson, Matthew Swallows, Michael Martin, Michael Bishof, Yige Lin, Jun Ye Due to its extremely narrow electronic transition and the decoupling between its nuclear spin from the electronic angular momentum, Sr has been featured in a number of Quantum Simulation proposals [1,2]. With the demonstrated capability in precision measurement and control from ongoing optical clock experiments, a key challenge to these quantum information experiments is the creation of high phase space density samples of both bosonic and fermionic Sr atoms at a high duty cycle. Here we report our recent progress in exploring novel cooling schemes with $^{88}Sr$. Recent results in employing Optical Feshbach Resonances for turning on interactions between atoms are presented and future experiments with narrow line laser cooling are discussed. \\[4pt] [1] A.J. Daley et al.\ 2008, 101, 170504\\[0pt] [2] A.V. Gorshkov et al.\ 2009, 102, 110503 [Preview Abstract] |
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E1.00119: Single site addressability in optical lattices Christof Weitenberg, Jacob Sherson, Manuel Endres, Marc Cheneau, Ralf Labouvie, Rosa Gloeckner, Immanuel Bloch, Stefan Kuhr Single site resolution in short-wavelength optical lattices, which have a significant tunnel coupling, is a challenging task. We prepare a BEC of rubidium atoms in a 3D lattice of 532 nm spacing. Using the 5S1/2 to 6P3/2 transition at 420nm, our imaging system (NA=0.7) will yield a resolution of 380nm and there-fore allow single site resolved detection and manipulation. So far we have taken in trap fluorescence images with a resolution of 700 nm using the 5S1/2 to 5P3/2 transition at 780nm and demonstrated the micro-manipulation of a few atoms with a tightly focused dipole trap. To extract one or a few slices and remove the atoms that are out of the depth of focus we use microwave transitions in a magnetic field gradient. The single site resolution will open up a new class of experiments in quantum simulation of strongly correlated systems - like the in-situ observation of the Mott insulator or the investigation of non-equilibrium phenomena - and in quantum information processing - like local spin manipulation or quantum gates with Rydberg atoms. [Preview Abstract] |
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E1.00120: High atom number using bichromatic forces in microsized atom traps J.M. Grossman, S. DeSavage, C.L. Adler, F.A. Narducci There is currently a push to develop miniaturized ultracold-atom devices for a variety of applications. Atom chips --- microscopic magnetic traps formed by current-carrying wires on a substrate --- present one route to achieve this miniaturization. Unfortunately, the number of atoms captured in a magneto-optical trap (MOT) scales as the fourth power of the radius of the trapping beams. For many applications, this directly translates to a reduction in signal-to-noise ratio. It is desirable, therefore, to find a method to recover a sizeable portion of the lost atoms without significantly increasing the complexity of the overall device. Rather than relying on absorption followed by spontaneous emission, bichromatic forces rely on absorption and stimulated emission. This force is in principle limited only by the intensity of the laser used and can greatly exceed the force exerted on an atom by a single laser field. While bichromatic forces are known to work in 1-D, their effect in 3-D still needs to be studied. Furthermore, bichromatic fields have been used for cooling, but not for trapping. In this poster, we describe the design of our apparatus to study 1-D and 2-D bichromatic fields, and present some of our preliminary measurements. [Preview Abstract] |
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E1.00121: Progress towards an experimental study of microscopic dipole trap loading and an investigation of atom dynamics in configurable microscopic double-wells Tyler Blum, Pasad Kulatunga We present our progress towards an experiment to investigate microscopic optical dipole traps, trap loading and atom dynamics in microscopic optical traps. Loading mechanics of large dipole traps from a laser cooled atomic molasses or a magneto-optically trapped atoms have been extensively investigated, and the loading dynamics are relatively well understood. While microscopic traps are finding increasing number of uses, little is known of the loading dynamics or of the optimal loading conditions. Several recent experiments of sub-micron traps have found size dependent differences in the loading dynamics. We propose to investigate loading dynamics as well as the lifetime and the temperature of dipole traps of waist 8 $\mu $m to $\sim $2.5 $\mu $m. Also microscopic dipole traps that we propose to study are well suited for investigating the dynamics of atoms of two adjacent microscopic traps. We also propose to investigate atoms in two adjacent dynamically configurable traps to study the effect of the presence of one trap on the other separated by a variable barrier height. Finally a collection of atoms localized to a very small volume in space lends to studying an untested cooling scheme particularly suited for deep microscopic traps. We also propose to investigate this cooling scheme. [Preview Abstract] |
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E1.00122: Impact of Hyperfine Repumping during Sub-Doppler Cooling with Large Detuning in $^{87}$Rb Rebekah Ferrier, Jacob Roberts As part of our investigation into long-range disruptive collisions during optical trap loading, we have developed a 1-D Quantum Monte Carlo code to simulate $\sigma^{+}-\sigma^{-}$ sub-Doppler cooling that includes hyperfine repumping. At the relatively large cooling laser detunings and low hyperfine repump powers appropriate for optimal optical trap loading conditions, we found that the polarization properties of the hyperfine repump light play a significant role during the cooling, including the relative polarization between the cooling and repump light fields. The results of our simulations will be described. [Preview Abstract] |
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E1.00123: Laser cooling of Ho atoms for collective encoding of a quantum register Jinlu Miao, Jacob Covey, Mark Saffman Ho atoms have 128 hyperfine ground states (the most of any stable atomic isotope) which may be used to collectively encode a large quantum register. We present progress towards laser cooling of Ho atoms using the $|4f^{11}6s^2, J=15/2\rangle \rightarrow |4f^{11}6s6p, J=17/2 \rangle$ transition at 410.5 nm. The design for a long lifetime optical trap using near 400 nm light will also be discussed. [Preview Abstract] |
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E1.00124: Optical trapping of ultra-cold 87Rb with a 1550nm laser Ping Wang, Abraham Olson, Qianli Ma, Sourav Dutta, Yong P. Chen We have optically trapped ultra-cold $^{87}$Rb atoms in a crossed optical dipole trap (ODT) with an IPG 50W, 1550nm single frequency erbium fiber laser and investigated various schemes to directly load the ODT from a magneto optical trap (MOT). After we initially collect 2$\times $10$^{8}$ atoms in the MOT and cool them to $\sim $20 $\mu $K by polarization gradient cooling, two crossed 1550nm laser beams are applied to the cloud and transfer $\sim $60{\%} of the atoms to the ODT. The alignment of the optical trapping beams with MOT is greatly facilitated by a large (several hundred MHz) AC stark shift of $^{87}$Rb 5P$^{3/2}$ excited states due to the 1550nm laser which is close to the 1529nm transition from 5P$^{3/2}$ to 4D$^{3/2 }$[1]. The cooling and repumping laser (780nm) of MOT become off resonant when dipole trapping lasers are aligned with MOT, ``buring'' a hole in what otherwise would be a bright MOT. After successful loading of the ODT, we have investigated various schemes of forced evaporative cooling in ODT. Our continued research will focus on Bose Einstein condensation and two dimensional atomic gas with this apparatus. \\[4pt] [1] J. P. Brantut, \textit{et al}., Phys. Rev. A \textbf{78}, 031401(R) (2008). [Preview Abstract] |
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E1.00125: Highly Efficient Production of an Absolute Ground State Dipolar Molecular Bose-Einstein Condensate Pierre Phou, Matthew Mackie We model formation of dipolar molecular condensate via Raman photoassociation of a two-component BEC, focusing on one- and two-step Landau-Zener sweeps of the laser detuning. In a one-step scheme, atoms are converted directly to absolute ground state molecules. In a two-step scheme, an initial sweep converts atoms to ground-electronic molecules in a high-lying vibrational state, and a second sweep converts the vibrationally-excited molecules into absolute ground state molecules. Realistic complications include rogue dissociation, spontaneous decay, elastic and inelastic collisions. The one-step scheme allows for high densities and more molecules, but requires high laser intensity to simultaneously overcome spontaneous decay and elastic collisions. On the other hand, a two-step scheme allows for low intensity but produces fewer molecules, since inelastic collisions require low densities. [Preview Abstract] |
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E1.00126: Towards the creation of few-body atomic Fock states Kirsten Viering, Gabriel N. Price, David Medellin, Jianyong Mo, Mark G. Raizen We report on our progress towards the production of few-body Fock states of atoms. Earlier work in our group demonstrated sub-Poissonian atom statistics in a system of bosonic Rubidium atoms, in agreement with our proposed method of laser culling. An analysis of a system of fermionic Lithium atoms shows the prospect of producing an atom ``on demand'' with ultra-high fidelity. To this end we are building a new experimental setup using Lithium which will improve upon previous results. The current status of the experiment is discussed. [Preview Abstract] |
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E1.00127: Apparatus for fermion atomic clock, atom interferometry and quantum pumping experiments M.K. Ivory, A. Ziltz, J. Field, S. Aubin We present the current state of an apparatus designed to create and manipulate ultracold bosonic and fermionic Rb and K isotopes for a fermion atomic clock, atom interferometry, microwave trapping, and quantum pumping experiments. Quantum pumping is a phenomenon which can precisely control bias-less flow of single electrons in a circuit. Using ultracold atoms on atom chips, we can test theoretical predictions which have not yet been verified due to experimental difficulties in solid state systems. The apparatus design consists of a magneto-optical trap, magnetic transport system, atom chip, and optical dipole trap. We have demonstrated basic laser cooling and trapping and are working towards transport of the collected atoms to the atom chip for cooling to quantum degeneracy. Once quantum degeneracy is achieved at the chip, micro-magnetic reservoirs of ultracold atoms connected by a 1D ``wire'' create a circuit for various quantum pumping schemes. These schemes are also more broadly applicable to atomtronics experiments. [Preview Abstract] |
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E1.00128: Dual potassium-cesium MOT for production of ultracold molecules Marin Pichler, David Hall, Michael Garman, Daniel Barker We present our setup for simultaneous trapping of potassium and cesium atoms in a dual MOT. Our goal is to use the trapped atoms to form ultracold $KCs$ molecules by photoassociation. The setup consists of all diode lasers for $Cs$ and a tapered amplifier for $K$ atoms cooling. In addition, we also use diode lasers for photoassociation. The setup relies on trap-loss or ion detection. We will discuss possibilities for deeply bound ground state molecule production via state coupling, as well as resonant multi-photon detection schemes and applications. [Preview Abstract] |
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E1.00129: Towards Photoassociation and Coherent Control of Cold LiRb Molecules John Lorenz, Adeel Altaf, Sourav Dutta, Daniel S. Elliott, Yong P. Chen We present our progress in creating and coherently controlling cold LiRb molecules. We have set up a dual-species $^{7}$Li/$^{85}$Rb magnet-optical trap. Studies of how densities of one atomic species are affected by the presence of another trapped atomic species allow us to probe $^{7}$Li-$^{85}$Rb collisional cross section. We seek to create cold LiRb molecules via photoassociation and detect production of LiRb using trap loss spectroscopy. Once LiRb molecules are created, we will explore controlling molecular alignment and orientation using optical coherent control. One possible method of control entails using quantum interference between multiphoton photoassociation processes to selectively create oriented molecules. Our technique may have possible applications in polar molecule based qubit operations taking advantage of the large dipole moment of LiRb. [Preview Abstract] |
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E1.00130: Towards Raman Cooling of a Single Atom in a Tightly Focused Optical Tweezer Jianwei Lee, Syed Abdullah Aljunid, Martin Paesold, Brenda Chng, Gleb Maslennikov, Christian Kurtsiefer When loading a single Rb atom from a magneto-optical trap into a tightly focused optical dipole trap we infer an average kinetic energy corresponding to a temperature of tens of microkelvin from release/recapture experiments. In order to bring the atom close to the vibrational ground state of the trap with characteristic frequencies of 20-60 kHz, we implement a Raman cooling technique similar to the one commonly used in ion traps. We expect to resolve the vibrational sidebands. This will lead to a better localization of the atom in free-space atom-photon interaction experiments. We present current experimental progress towards this goal. [Preview Abstract] |
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E1.00131: Trapping single Cs atoms in an optical bottle beam Siyuan Zhang, Kara Maller, Johannes Nipper, Mark Saffman We have implemented a microscopic optical bottle beam (BoB) trap using 532 nm light focused to waists of $w=2$ and $4~\mu\rm m$. We obtain calculated trap depths $>100~\mu\rm K$. The BoB trap has the potential for stable trapping of both ground state and Rydberg atoms. We have superimposed the BoB trap with a Cs magneto-optical trap, and will report progress towards observation of single trapped Cs atoms. [Preview Abstract] |
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E1.00132: Cooling and trapping of Single Yb atom in a high-finesse optical cavity Yujiro Eto, Atsushi Noguchi, Peng Zhang, Masahito Ueda, Mikio Kozuma Nuclear spin of $^{1}$S$_{0}$ ground state of Yb atom is a promising candidate of quantum bit, because the coherence time is much longer than that for the electric spin and its information can be transferred to flying qubit (photon) through the hyperfine interaction. Recently projective measurements were performed on single nuclear spin of Yb atom by using such a hyperfine interaction and also the cavity QED technique.\footnote{Takeuchi \textit{et al.}, arXiv:0907.0336.} However, the operation time for the qubit was limited to an extremely short time ($\sim $100us) because freely falling atoms was used for the experiment. While there exists an efficient cooling method using a cavity-induced Purcell effect, experiments have been demonstrated so far only for alkali atoms such as Rb and Cs. Here we report the first implementation of the cavity-assisted cooling for single Yb atom in a high-finesse optical cavity. The trapping time of a few second has been achieved and clear quantum jump was monitored, where the cooling was performed using the $^{1}$S$_{0}-^{3}$P$_{1}$ intercombination transition (556 nm). [Preview Abstract] |
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E1.00133: Progress Towards Single-site Imaging of Fermions in an Optical Lattice Dylan Jervis, David McKay, Hai Jun Cho, Michael Sprague, Matthias Scholl, Karl Pilch, Jason McKeever, Joseph H. Thywissen We discuss progress towards in-situ imaging of a single plane of fermionic $^{40}$K atoms in an optical lattice. Spin-sensitive in- situ imaging will allow for local measurements of occupation, spin ordering, and domain structure of interesting many-body phases, including band insulators, Mott insulators, Neel antiferromagnets, superfluid states, and striped or other structured ordering. We are currently testing a design that collects light from the 405 nm $\mathit{4S}\rightarrow\mathit{5P}$ transition of $^{40}$K through a thin (200 micron) vacuum window and have demonstrated a resolution of better than 550 nm. We have also used saturation spectroscopy to lock a laser to the $\mathit{4S}\rightarrow\mathit{5P}$ transition, allowing for narrow-line Doppler cooling. [Preview Abstract] |
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E1.00134: MOLECULAR SPECTROSCOPY |
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E1.00135: Cavity-Enhanced Direct Frequency Comb Velocity Modulation Spectroscopy Laura Sinclair, Kevin Cossel, William Ames, Jun Ye, Eric Cornell We have developed a novel technique for broad bandwidth and high resolution survey spectroscopy of molecular ions. Cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) provides broad bandwidth and high resolution by using individual comb lines as parallel detection channels. Here we combine CE-DFCS with velocity modulation spectroscopy to provide ion-specific detections with further enhanced sensitivity. A 2-dimensional lock-in camera is used for real-time demodulation across many simultaneous detection channels. This technique has broad applications for spectroscopy on molecular ions. The first application of this technique will map the electronic states of HfF$^+$ and ThF$^+$. Trapped molecular ions provide large effective electric fields and long coherence times for search of a permanent electron electric dipole moment (eEDM); however, the electronic state structure of HfF$^+$ and ThF$^+$ are not well known. Determination of the $^3\Delta_1$ potential, its coupling to various excited states, and the corresponding rovibrational levels is integral to the JILA eEDM measurement. [Preview Abstract] |
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E1.00136: Collisional molecular orientation transfer in polarization spectra of the A$^{1}\Sigma _{u}^{+ }$state of $^{85}$Rb$_{2}$ and Cs$_{2}$ dimers Jianmei Bai, Bediha Beser, Ergin Ahmed, Yafei Guan, Christopher Wolfe, Seth Ashman, John Huennekens, Marjatta Lyyra There is significant interest in the lowest excited states of the heavy alkali dimers since they serve as intermediaries in the excitation to higher levels and in the production of ultracold ground state molecules. We have observed a large number of rovibrational levels of the A-b complex in $^{85}$Rb$_{2}$ and Cs$_{2}$ using V-type optical-optical double-resonance polarization spectroscopy with a circularly polarized pump laser and a linearly polarized separate probe laser. In addition to the $R$, $P $doublets, expected from a single pump laser lower level, we have observed orientation transfer based probe laser signals from a large number of collisionally populated rotational levels. Despite the complex collisional processes occurring in the system, satellite lines with significant difference in the rotational quantum number from the main lines (up to $\Delta $J = 52 in $^{85}$Rb$_{2})$ are present in the recorded spectra. The measurements were performed using a heatpipe oven. [Preview Abstract] |
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E1.00137: Towards Trapping of Ba Ions for Heavy Molecule Spectroscopy Joan Marler, J.H.V. Nguyen, C-Y. Lien, Y-W. Lin, V. Rajagopal, C. Seck, D.A. Tabor, G. McGlynn, L. Ruth, B. Odom Precisely because of their rich internal structure, molecules are much more difficult to control than atoms. By laser-cooling co-trapped atomic ions, we intend to sympathetically cool molecular ions to milliKelvin temperatures, where velocities and environmental interactions are reduced. A possible scheme for further cooling to the rotational ground state of the molecule will be presented. Precision measurements on such molecules should shed light on slight difference in the vibrational levels of chiral molecules and possible changes in the fundamental constants. [Preview Abstract] |
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E1.00138: Molecular Spectroscopy in Hollow-Core Photonic Crystal Fiber at the 10 kHz Level Chenchen Wang, Kevin Knabe, Shun Wu, JinKang Lim, Karl Tillman, Brian Washburn, Kristan Corwin, Natalie Wheeler, Francois Couny, Fetah Benabid High-accuracy spectroscopy in hollow-core photonic crystal fiber (HC-PCF) is desirable for many applications, including frequency references and trace gas analysis. We demonstrate the narrowest sub-Doppler linewidths attained in HC-PCF using large-core kagome structured fiber. Such fibers can yield highly accurate frequency measurements that are about two orders of magnitude higher than previously reported. A fiber laser is locked to the $^{12}$C$_{2}$H$_{2} \quad \nu _{1}+\nu _{3}$ P(13) transition inside kagome fiber, and compared with two optical frequency combs referenced to a GPS-disciplined Rb oscillator. The absolute frequency of the measured line center agrees with those measured in power build-up cavities to within 9.3 kHz (1 $\sigma $ error). Approaches to further narrow the linewidths and improve systematic errors are investigated. The present system thus combines accuracy approaching that of power build-up cavities with the potential to be compact, robust, and integrated into an all-fiber system for a portable near-infrared frequency reference. Supported by AFOSR FA9950-05-1-0304 and NSF ECS-0449295. [Preview Abstract] |
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E1.00139: Experimental Studies of the NaCs 5$^{3}\Pi _{0}$ and 1($a)^{3}\Sigma ^{+}$ States Seth Ashman, Brett McGeehan, Christopher Wolfe, Carl Faust, John Huennekens We present experimental studies of the NaCs molecule that are currently underway in our laboratory. The optical-optical double resonance method is used to obtain Doppler-free excitation spectra for several excited states. Selected data from the 5$^{3}\Pi _{0}$ electronic state are used to obtain Rydberg-Klein-Rees (RKR) and Inverse Perturbation Approach (IPA) potential curves. We are also mapping the repulsive wall of the 1($a)^{3}\Sigma ^{+ }$potential using many resolved bound-free fluorescence spectra from individual ro-vibrational levels of the 5$^{3}\Pi _{0}$ electronic state to the 1($a)^{3}\Sigma ^{+}$ state. Using the determined 5$^{3}\Pi _{0}$ state potential we fit the repulsive wall of the 1($a)^{3}\Sigma ^{+}$ state to reproduce the experimental spectra using LeRoy's BCONT program. A slightly modified version of BCONT is also used to fit the relative transition dipole moments, \textit{$\mu $}$_{e}(R)$, as a function of internuclear separation $R$, for the various bound-free electronic transitions. [Preview Abstract] |
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E1.00140: PLASMAS |
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E1.00141: Modeling Of Low-Z Plasma Spectroscopy Results from NSTX and Compact ``Sparky'' Plasma Facilities P. Cox, A. Safronova, V. Kantsyrev, A. Esaulov, U. Safronova, K. Williamson, M. Weller, J. Lepson, P. Beiersdorfer New non-LTE kinetic models of Li and B as well as previously developed and applied models of C and O, updated now with more high-Rydberg states, have been utilized in the modeling of recent experimental spectra from NSTX and compact laser plasma facility ``Sparky''. Emphasis was placed on the examination of EUV and soft x-ray Oxygen and Carbon spectra from both devices. In addition, Lithium and Boron lines from NSTX spectra were identified and used for benchmarking of corresponding kinetic models. The considered NSTX spectra cover the spectral range from 20 {\AA} to 200 {\AA}, where OVI and OV are the most dominant Oxygen ionization stages. Also, the most intense lines from He-like ions of C and H-like B ions in the soft X-ray region in first order of reflection have been observed. Prominent carbon and oxygen features from NSTX Tokamak experimental spectra were compared with those from ``Sparky'' and the most diagnostically significant temperature and density sensitive lines identified for use as future diagnostic tools. Research supported by DOE under grant DE-FG02-08ER54951 and by NNSA Coop. Agreements DE-FC52-06NA27588 and DE-FC52-06NA27586. [Preview Abstract] |
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E1.00142: Simulation of ultracold plasmas using the Monte Carlo method D. Vrinceanu, G.S. Balaraman After creation of the ultracold plasma, the system is far from equilibrium. The electrons equilibrate among themselves and achieve local-thermal equilibrium on a time scale of few nano-seconds. The ions on the other hand expand radially due to the thermal pressure exerted by the electrons, on a much slower time scale (microseconds). Molecular dynamics simulation can be used to study the expansion and equilibration of ultracold plasmas, however a full micro second simulation are computationally exorbitant. We propose a novel method using Monte Carlo method for simulating long timescale dynamics of a spherically symmetric ultracold plasma cloud [1]. Results from our method for the expansion of ion plasma size, and electron density distributions show good agreement with the molecular dynamics simulations. Our results for the collisionless plasma are in good agreement with the Vlasov equation. Our method is very computationally efficient, and takes a few minutes on a desktop to simulate tens of nanoseconds of dynamics of millions of particles. \\[4pt] [1] D. Vrinceanu, G. S. Balaraman and L. Collins, ``The King model for electrons in a finite-size ultracold plasma,'' J. Phys. A, 41 425501 (2008) [Preview Abstract] |
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E1.00143: Masked Ionization Experiments in Ultracold Nuetral Plasmas Patrick McQuillen, Jose Castro, Thomas Killian Evidence of shock and ion acoustic waves have been seen in shadow mask ionized Ultracold Neutral Plasmas. By spatially modulating the intensity of the ionizing beam, the typical spherical Gaussian symmetry is broken. This controllable geometry along with spatial-temporal fluorescence spectroscopy has revealed density front collisions and ion velocity oscillations. These results and their interplay with the effects of strong coupling will be shown. [Preview Abstract] |
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E1.00144: Density scaling of disorder-induced heating in ultracold neutral plasmas Scott Bergeson, Francis Robicheaux We present measurements and simulations of disorder-induced heating (DIH) in the first 100 ns after plasma formation. We study plasmas with peak densities up to $4\times 10^{10}$ cm$^{- 3}$ and initial electron temperatures up to 60 K using laser- induced fluorescence on the plasma ions. Rabi oscillations, DIH, and plasma expansion are clearly visible in the fluorescence signals. [Preview Abstract] |
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E1.00145: Diffraction imaging with electrons from an ultracold plasma source S.D. Saliba, D.V. Sheludko, A.J. McCulloch, M. Junker, S.C. Bell, H.M. Quiney, R.E. Scholten The molecular structure of biological molecules such as bacteriorhodopsin can be determined by electron diffraction, but general application has been limited by the brightness of conventional electron sources. Brightness is proportional to current and inversely proportional to electron temperature. A high brightness electron source from cold atom clouds presents a promising alternative to traditional high temperature (104 K) sources. Cold atoms in a MOT can be photoionized just above threshold, releasing electron bunches with temperatures as low as 10 K. Although the number of electrons that can be extracted from a MOT is relatively small, the reduced temperature may enable brightness competitive with conventional alternatives. We have simulated electron diffraction from electron microscopy grids and 2D arrays of simple molecules, exploring the energy, coherence and brightness requirements for practical diffraction imaging. [Preview Abstract] |
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E1.00146: Ultracold plasma electron source for diffractive imaging M. Junker, S.C. Bell, D.V. Sheludko, A.J. McCulloch, R.E. Scholten Ultracold plasmas have made the prospect of high brightness electron beams a promising alternative to conventional high temperature (10$^{4 }$K) sources. We have created a Zeeman slowed MOT of $^{85}$Rb atoms, which was photoionized near the ionization threshold. The pulsed electron bunches were accelerated by an electrostatic field up to 200~V/cm between parallel accelerator plates and focused using a third electrode. The electrons were characterized using a microchannel plate, phosphor screen, and CCD camera. We are investigating the coherence and brightness of the extracted electron bunches, and particularly, the effect of controlling the initial atomic spatial distribution to generate a uniform elliptical charge distribution. Such elliptical bunches intrinsically preserve their brightness, and can be refocused with conventional accelerator techniques. [Preview Abstract] |
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E1.00147: Rydberg atom formation in strongly correlated ultracold neutral plasmas Georg Bannasch, Thomas Pohl In plasmas at very low temperatures the recombination into neutral atoms is dominated by three-body recombination (TBR), owing to the strong $\sim T^{-9/2}$ scaling of the recombination rate with the electron temperature. While this law is well established at high temperatures, the unphysical divergence as $T\rightarrow0$ clearly suggest a breakdown in the low-temperature regime. Here, we use a combined molecular dynamics - Monte Carlo approach to investigate electron-ion recombination over a wide range of temperatures and densities. Through a careful analysis, we devise an approach that permits to distinguish recombined atoms from the surrounding plasma, i.e. to develop a chemical picture $-$ even in the strongly coupled regime. Our method reproduces the known behavior of the recombination for high temperatures, but reveals significant deviations as $T$ decreases. We discuss the fate of the kinetic bottleneck and resolve the discussed divergence-problem in the ultracold domain. [Preview Abstract] |
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E1.00148: Thermalization and Cooling of Cold, Highly-Magnetized, One-Component Plasmas Alex Povilus, Steve Chapman, Marcelo Baquero-Ruiz, Crystal Bray, Joel Fajans Thermalization of strongly-magnetized plasmas relies on the dynamics of particle collisions and interaction with the background electromagnetic field. The nature of these interactions changes greatly as a plasma is cooled to lower temperatures. In particular, these effects can have a large effect on techniques requiring sympathetic cooling through cyclotron radiation of a cloud of electrons. With the intention of cooling dense ($\sim 10^9 / \rm{cc}$) non-neutral plasmas to $4 \rm{K}$, we model the various mechanisms that are important in this regime. As a one-component plasma cools, the transverse and longitudinal degrees of motion become decoupled in collisions, inhibiting thermalization. Electromagnetic cavity modes from electrodes can couple to the plasma, inducing heating. The plasma can also become optically opaque to its own cyclotron radiation, reducing the efficiency of cyclotron cooling. Here, we present a model for these mechanisms and a proposed experiment for characterizing their behavior. [Preview Abstract] |
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E1.00149: The Effect of Multipole-Enhanced Diffusion on the Joule Heating of a Cold Non-Neutral Plasma Steven Chapman, Alex Povilus, Joel Fajans One proposed technique for trapping anti-atoms is to superimpose a Ioffe-Pritchard style magnetic-minimum neutral trap on a standard Penning trap used to trap the charged atomic constituents. Adding a magnetic multipole field in this way removes the azimuthal symmetry of the ideal Penning trap and introduces a new avenue for radial diffusion. Enhanced diffusion will lead to increased Joule heating of a nonneutral plasma, potentially adversely affecting the formation rate of anti-atoms and increasing the required trap depth. We present a model of this effect with comparison to measurements from an intended anti-atom trap. [Preview Abstract] |
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E1.00150: Role of anisotropic particle scattering in hydrogen Townsend discharge Zoran Petrovic, Vladimir Stojanovic, Zeljka Nikitovic In this work we show results of Monte Carlo modeling of electrons and heavy particle induced spatially resolved emission intensity and the Doppler profiles of H lines in pure H$_{2}$ discharge focusing on anisotropy of elastic scattering of heavy particles. Electron transport is also modeled by using available differential scattering cross sections. For most intense inelastic scattering processes of heavy particles we used the simplest assumptions. For electrons, H$^{+}$, H$_{2}^{+}$, H$_{3}^{+}$, fast H and H$_{2}$ we modeled scattering in collisions with the electrodes and with molecules. In particular we analyze how transport of H$^{+}_{ }$and fast H particles is affected by the choice of the model of anisotropic scattering. In order to achieve consistency with the results of other authors we select conditions of simulation appropriate for moderate $E/N$ ($E$-electric field, $N$-gas density) that are selected from experimental Townsend discharges in pure H$_{2}$. Excellent agreement with experimental results is achieved only when anisotropic scattering is taken into account. [Preview Abstract] |
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E1.00151: Reduction of Mixing-Length Transport by Radio Frequency Waves S. Sen Numerical simulation is carried out by using the ASTRA code to determine the effect of mixing-length transport induced in a plasma in the presence of radio-frequency waves. It is found that the transport coefficients associated with particle diffusion and heat diffusion reduce drastically in the region where radio waves is launched. This technique opens up a new avenue of transport suppression by the use of radio waves of suitable frequency. [Preview Abstract] |
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E1.00152: Plasma Oscillations in the Presence of Radio Frequency Waves S. Sen The effect of the radio-frequency (RF) waves on the low-frequency plasma oscillations is investigated. It is found that the crucial factor whether the plasma oscillations will be quenched or excited depends on the gradient of the RF power deposition profiles from the mode rational surfaces where the RF power is deposited. If the gradient is positive then the plasma oscillations are excited whereas for the negative value of the gradient the oscillations are suppressed. This result is interesting for the plasma oscillations control in a low temperature plasma device. [Preview Abstract] |
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E1.00153: Dielectronic satellite spectra of Li-like ions calculated using relativistic many-body theory for spectroscopy of high-$Z$ multiply-charged ion plasmas U.I. Safronova, A.S. Safronova, W.R. Johnson The importance of dielectronic satellite spectra of Li-like ions as a plasma diagnostic has been recognized for almost forty years. In particular, dielectronic satellites (DS) created by $1s2lnl'$ autoionizing states in mid-$Z$ ions have been extensively studied both in astrophysical and laboratory plasmas including Tokamak plasmas but not for $Z$ greater than 54. However, high-$Z$ materials such as tungsten will be used in plasma-facing components for future experiments at ITER and thus their spectroscopic data became very important. In this talk, we present relativistic many-body perturbation theory (RMBPT) calculations of dielectronic satellite spectra of Li-like ions and give a detailed discussion of the atomic data (energies, radiative transition rates and autoionization rates) that enter calculations of dielectronic recombination rates for such ions. We discuss these factors in detail for the important case of Li-like tungsten. Also synthetic spectra of dielectronic satellite lines ($1s2l2l'-1s^22l''$) are illustrated for Mo$^{39+}$ and W$^{71+} $ ions which are important for spectroscopy of high-temperature plasmas including tokamak plasmas. This research was sponsored by DOE under the OFES grant DE-FG02-08ER54951 and in part under the NNSA CA DE-FC52- 06NA27588. [Preview Abstract] |
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E1.00154: CLUSTERS, SOLIDS, AND SURFACES |
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E1.00155: Scattering of Electrons from Impurities in Graphene J.Y. Vaishnav, Charles W. Clark, J.D. Walls We develop a theoretical formalism to describe scattering of electrons in graphene from impurities. Our formalism applies to low-energy incident particles scattering from impurities much larger than the lattice constant. At long wavelengths, our formalism allows determination of all transport properties of the system via inversion of a $6N$ x $6N$ matrix, where $N$ is the number of impurities. We discuss how single and multiple scattering from impurities in graphene differ from scattering on ordinary metallic substrates. For example, due to the Dirac-like dispersion relation of graphene, even low-energy scattering from an impurity generates a combination of $s$ and $p$ waves. Our results are equally applicable to an atom scattering from other atoms confined in a honeycomb optical lattice. In this situation, the locations of impurities could be controlled, suggesting possible ``atomtronic'' device applications. [Preview Abstract] |
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E1.00156: Comparison of the bremsstrahlung yields from 53 keV electrons on solid-film gold targets produced by PENELOPE and experiment Sebastian Requena, Scott Williams, C.A. Quarles We compare the predictions for the absolute bremsstrahlung yields from 53 keV electrons on gold targets of the Monte Carlo program, PENELOPE, to experimental results. The program required several modifications in order to compare the data obtained at a backward angle of 90 degrees. A comparison of the results indicates whether or not absolute yields from solid films are best described by ordinary bremsstrahlung alone, or whether they require the consideration of polarizational bremsstrahlung contributions. [Preview Abstract] |
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E1.00157: Survival of hydrogen anions near atomically flat metal surfaces: Band gap confinement and image state recapture effects Andrew Schmitz, John Shaw, Himadri Chakraborty, Uwe Thumm Resonant charge transfer (RCT) between ions and surfaces is a key intermediate step in surface-chemical processes as well as in micro- and nano-fabrications on the surface. The RCT process in the collision of hydrogen anions with metal surfaces is described within a wave packet propagation methodology using Crank-Nicholson algorithm [1]. The ion-survival probability is found to strongly enhance at two different ion velocities perpendicular to the surface. The low velocity enhancement is induced from a dynamical confinement of the ion level inside the band gap, while the high velocity enhancement emerges owing to the recapture from transiently populated image states [2]. These structures are found to be somewhat sensitive to the ion's distance of closest approach to the surface and the choice of inter-atomic potentials between the ion and the surface atoms. [1] Chakraborty et al., \textit{Phys. Rev.} A \textbf{70}, 052903 (2004); [2] Schmitz et al., \textit{Phys. Rev.} A (submitted). [Preview Abstract] |
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E1.00158: Dependence of the chemical sputtering of deuterated carbon on the surface temperature Mostafa Jonny Dadras, Predrag Krstic We study chemical sputtering of carbon irradiated by 1-30 eV deuterium atoms, in range of surface temperatures 300-1000 K. At each temperature and each impact deuterium energy a quasi-stationarity of the total carbon erosion is reached by cumulative bombardment. Dependence of the mass, energy and angular spectra of sputtered hydrocarbons, as well as density of the sp$^{3}$ and sp$^{2}$ moieties on the surface temperature are also studied. We compare our results with available experimental data on methane, acetylene and the total carbon sputtering. [Preview Abstract] |
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E1.00159: Potential Energy Functions for Metal Clusters and Nanoparticles Nicole Legenski, Robert C. Forrey, Hansong Cheng Atomic force fields for simulating copper, silver, and gold clusters and nanoparticles are developed. Potential energy functions are obtained for each metallic system using an embedded atom method with parameters that have an explicit dependence on coordination number. Many cluster configurations of varying size and shape are used to constrain the parametrization for each system. Binding energies for these training clusters were computed using density functional theory (DFT) with the Perdew-Wang exchange-correlation functional in the generalized gradients approximation. Extensive testing shows that the many-body potentials are able to reproduce the DFT energies for most of the near-equilibrium and many of the non-equilibrium structures that were included in the training set. Implications for molecular dynamics simulations and extensions to binary metallic systems and also to hydrogen on metallic clusters are discussed. [Preview Abstract] |
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E1.00160: High-Aperture Narrow-Band Moire Filter in Volume Bragg Grating Sergiy Mokhov, Julien Lumeau, Vadim Smirnov, Boris Zeldovich, Leonid Glebov We propose narrow-band filter in volume Bragg grating (VBG) with bandwidth less than ten picometers. Two recorded Bragg gratings with the same modulation amplitudes and slightly different resonant wavelengths form moire pattern with slowly varying envelope of modulation amplitude. Each semi-period of modulation is just apodized reflective VBG; however two of them together form narrow-band transmission Fabry-Perot cavity due to phase $\pi $-shift as result of sign change of slowly varying envelope. We fabricated first moire VBG filter in photo-thermo-refractive glass with resonance wavelength near 1550 nm, aperture size 5 mm, bandwidth 50 pm and 95{\%} maximum transmittance. We considered also case when carrier Bragg grating wave vector does not coincide with moire pattern wave vector which allows creating filters with tunable one-period envelope profile from sinusoidal function to cosinusoidal one. Doubled resonant cavity with cosinusoidal profile demonstrates flattop transmission peak. Analytical expression for tunable bandwidth was found. Robust solid-state moire VBG filters tolerant to high-power laser irradiation with tunable filtering characteristics are suggested as optical elements for laser design and spectroscopy applications. [Preview Abstract] |
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E1.00161: Measurement of the refractive index of highly turbid media Samir Bali, Eric Williams, Sarabjot Makkar, Miao Dong, Lalit Bali We demonstrate a first simultaneous measurement of the real and imaginary parts of the refractive index of a highly turbid medium (scattering coefficient $> 200$cm$^{-1}$; by comparison, milk's scattering coefficient in the visible and near-infrared frequencies lies between 40cm$^{-1}$ and 125cm$^{-1}$ depending on fat content). We achieve this by observing the real-time reflectance profile of a divergent laser beam made incident on the surface of the turbid medium. We find that the reflectance data is well described, for the first time without any empirical fit-parameters, by Fresnel theory that correctly includes the effect on total internal reflection of angle-dependent penetration into the turbid medium. [Preview Abstract] |
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E1.00162: Structures of $\sim 100$ nm Size Produced by Atom Lithography with Metastable He Jason Reeves, Christopher Corder, Xiaoxu Lu, Claire Allred, Harold Metcalf We have used neutral atom lithography with metastable 2$^3$S He (He*) to produce structures of size $\sim 100$ nm. A beam of He* from our source is collimated by the bichromatic force\footnote{M. Partlow et al., Phys. Rev. Lett. {\bf 93,} 213004 (2004)} and then by optical molasses. Atoms cross a standing wave of $\lambda =$ 389 nm light tuned $\sim$80 MHz below the 2$^3$S$_1 \rightarrow 3^3$P$_2$ transition and are focussed into lines striking a self assembled monolayer (SAM) of nonanethiol coated over a gold film on a single crystal Si wafer. The 20 eV internal energy of He* destroys the SAM molecules ultimately leaving a pattern of SAM on the gold. Subsequent etching of the unprotected region of the gold results in these features\footnote{C. Allred et al., submitted to J. Appl. Phys.}$^,$\footnote{C. Allred, Ph.D. Thesis, Stony Brook, NY (2009) - unpublished.}. The lines are separated by 194.5 nm and they occupy about 60\% of their spacing. AFM measurements of our first samples show their width to be $\sim 120$ nm and their depth to be $\sim 10$ nm. [Preview Abstract] |
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E1.00163: Composition-Structural-Electrical Properties of Yttrium-Stabilized Hafnium Oxide Films Deposited by Atomic Layer Deposition Qian Tao, Gregory Jursich, Christos Takoudis Sequential Atomic Layer Deposition was used to deposit yttrium-doped hafnium oxide films with variable yttrium content using tris (ethylcyclopentadienyl) yttrium, and tetrakis (diethylamino) hafnium as metal precursors and water vapor as the oxidizer. The structure and electrical properties of the resulting films were analyzed after different post-deposition annealing conditions to assess composition-structure-dielectric property relationships. 2.5--100{\%} yttrium-doped films annealed above 600$^{\circ}$C for 5 minutes consistently yielded cubic-HfO2 structures. However, there was a strong compositional effect on the dielectric constant, which maximized at $\sim $14{\%} yttrium content. The films studied had leakage current density of 10$^{-5}$ A/cm$^2$ or less at 1 V. [Preview Abstract] |
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E1.00164: ELECTRON COLLISIONS |
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E1.00165: Multichannel quantum-defect theory for electron-atom interactions with application to the atomic fine and/or hyperfine changing collisions by electron impact Bo Gao, Alexander Dalgarno We present a general multichannel quantum-defect theory for electron-atom interactions. It provides, in particular, a rigorous formulation for atomic fine and/or hyperfine changing collisions by electron impact. The theory is applied here to the hyperfine transition of atomic hydrogen by electron impact to show that the traditional elastic approximation fails for electron energies comparable to the hyperfine splitting. [Preview Abstract] |
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E1.00166: Imaging Electronic Motion with Attosecond Electron Pulses Hua-Chieh Shao, Anthony F. Starace Ultrashort electron pulses have been proposed to observe time-dependent phenomena in atoms and molecules [1]. Owing to the temporal and spatial resolutions of short keV electron pulses, studying electronic motion in attosecond and sub-Angstrom regimes is feasible. We report benchmark calculations for oscillating electronic charge distributions in the H atom and in the H$_2^+$ molecule to determine the effect of such charge oscillations on the elastic scattering cross section for a sub-fs electron pulse. In the pump/probe calculations, a femtosecond laser pulse is used to excite a coherent superposition of states, whose charge distribution oscillates with the beat frequency. The electron pulse scattering cross sections are calculated in the Born approximation. For the H atom, the cross section exhibits an oscillating effective radius. For the H$_2^+$ molecules, the superposed state is chosen such that the electronic charge distribution oscillates from one nucleus to the other; hence, the differential cross section shows the localization of the electron.\\[4pt] [1] P. Baum and A.H. Zewail, PNAS \textbf{104}, 18409 (2007). [Preview Abstract] |
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E1.00167: Electron-impact excited term ionisation along the Boron isonuclear sequence C.P. Ballance, T. Lee, J.A. Ludlow, S.D. Loch, M.S. Pindzola Non-perturbative theoretical methods over the last decade have mainly focused on electron-impact ionization of the ground and first metastable states for light fusion related species [1]. However, collisional-radiative models predict that effective ionisation rates, which include the ionisation from excited levels of an atom, can be an order of magnitude greater greater than those which include the groundstate alone. For example, this stepwise ionisation has been experimentally confirmed by measurements taken at the DIII-D facility as part of a Li transport study, where excited state ionisation was found to be essential in describing Li transport [2]. We shall present in our poster an overview of excited state ionisation along the boron ionisation sequence. Using boron as a test case, we focus on the most appropriate use of computationally non-perturbative methods and simpler non-pertubative/semi-empirical methods to account for excited ionisation along other iso-nuclear sequences.\\[4pt] [1] Griffin D C and Pindzola M S, Adv. Atm. Mol. Opt. Phys. 54, 203 (2006)\\[0pt] [2] Allain J P, Whyte D G and Brooks J N, Nucl. Fusion 44 655 (2004) [Preview Abstract] |
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E1.00168: Electron-impact excitation calculations for the argon iso-nuclear sequence S.D. Loch, C.P. Ballance, J.A. Ludlow, M.S. Pindzola We present results from recent Breit-Pauli $R$-matrix calculations for the electron-impact excitation of select Argon ions, namely Ar$^{3+}$, Ar$^{4+}$, Ar$^{5+}$, Ar$^{7+}$, Ar$^{8+}$, Ar$^{10+}$, Ar$^{11+}$, Ar$^{12+}$, Ar$^{13+}$, Ar$^{14+}$, and Ar$^{17+}$. Together with existing R-matrix calculations this provides a complete excitation dataset for the Argon isonuclear sequence. This project provides a comprehensive set of excitation data for use in current fusion diagnostics, where argon is used to cool the divertor or to mitigate plasma disruptions. The data will also be used in future calculations of generalized collisional-radiative coefficients, for application in plasma transport studies. The $R$-matrix calculations were done using new developments in the parallel $R$-matrix codes, allowing the complete iso-nuclear sequence to be calculated relatively quickly. We present results for selected ions, showing a comparison with available excitation cross section measurements, and with other structure and collision strength calculations. We also present some radiative power loss results using the new data. The data is archived as Maxwellian averaged rate coefficients. [Preview Abstract] |
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E1.00169: Cross sections for electron scattering from S II Swaraj Tayal, Oleg Zatsarinny The improved atomic calculations for electron impact excitation cross sections for S II have been performed using the B-spline Breit-Pauli R-matrix method. The flexible non-orthogonal sets of spectroscopic and correlation radial functions are employed for an accurate representation of the target states and to represent scattering functions. The close-coupling expansion includes 70 bound levels of S II covering all possible terms of the ground $3s^23p^3$ and excited $3s3p^4$, $3s^23p^23d$, $3s^23p^24s$, and $3s^23p^24p$ configurations. The calculated excitation energies of the target levels are in excellent agreement with experiment and represents an improvement over the previous calculations. The present results of cross sections are compared with variety of other close-coupling calculations and available experimental data. The present results are in good agreement with other theories and experiment for the $3s^23p^3$ $^4S^o$ $\rightarrow$ $^2D^o$ transition, but some differences in magnitude and shape for the forbidden $3s^23p^3$ $^4S^o$ $\rightarrow$ $^2P^o$ and resonance $3s^23p^3$ $^4S^o$ $\rightarrow$ $3s3p^4$ $^4P$ transitions are noted. [Preview Abstract] |
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E1.00170: Electron Impact Excitation Collision Strengths of Transitions in Fe XII Swaraj Tayal Electron impact excitation collision strengths for transitions between the fine-structure levels of the ground $3s^23p^3$ and excited $3s3p^4$, $3s^23p^23d$, $3s^23p^33d$, and $3p^5$ configurations in Fe XII have been calculated using the B-spline Breit-Pauli R-matrix method. The multiconfiguration Hartree-Fock method with term-dependent non-orthogonal orbitals is employed for an accurate representation of the target wave functions. There is strong configuration-interaction mixing among different even parity states of the $3s3p^4$ and $3s^23p^23d$ configurations. The spin-orbit interaction for the levels of the $3s^23p^2(^1D)3d~^2F$ and $3s^23p^2(^3P)3d~^2F$ terms is strong. The calculated excitation energies are in excellent agreement with the experimental values. The close-coupling expansion included 90 bound levels of Fe XII, and the relativistic effects have been incorporated through mass, Darwin, and spin-orbit one- body operators in the Breit-Pauli Hamiltonian in the scattering calculation. The present results are compared with available other close-coupling calculations. Overall very good agreement was found for many transitions, but some significant differences were also noted. [Preview Abstract] |
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E1.00171: M-Shell Dielectronic Recombination for the Al-Like Isoelectronic Sequence Sh. A. Abdel-Naby, T.W. Gorczyca, N.R. Badnell Dielectronic recombination (DR) is the dominant electron-ion recombination process for most ions in both photoionized and collisionally-ionized plasmas and plays a central role in determining the charge state balance and spectra of these plasmas. Accurate DR rate coefficients are thus essential for modeling astrophysical plasmas. We have carried out extensive DR calculations for the Al-like isoelectronic sequence using a state-of-the-art multi-configuration Breit-Pauli (MCBP) approach. We present total rate coefficients for both DR and radiative recombination (RR) for Al-like iron peak ions (V$^{10+}$- Ni$^{15+}$) along with Cu$^{16+}$ and Zn$^{17+}$ spanning a temperature range of $z^2(10 - 10^7)$K, where $z$ is the initial ion charge. The Fe$^{13+}$ results are benchmarked to the experimental measurements from the Heidelberg Test Storage Ring. Both LS and intermediate coupling (IC) schemes are considered. We also present DR + RR fitting coefficients for both ground and meta-stable levels of all ions. [Preview Abstract] |
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E1.00172: Stable excited Au\={ } and Pt\={ } negative ions: A Regge-pole prediction Z. Felfli, A.Z. Msezane, D. Sokolovski Electron elastic scattering from Au and Pt atoms is investigated in the energy region E $<$ 4.0 eV in search of the possibility of forming and observing stable excited Au\={ } and Pt\={ } negative ions as Regge resonances. Total elastic cross sections (TCSs) and differential cross sections (DCSs) in both impact energy and scattering angle for the excited Au and Pt atoms are calculated. The investigation uses the recent Regge-pole methodology [1] wherein is embedded the vital electron-electron correlations together with a Thomas-Fermi type potential that incorporates the crucial core-polarization interaction, essential for the existence and stability of most negative ions. From the characteristic dramatically sharp resonances in the elastic total and Mulholland partial cross sections we identify excited Au\={ } and Pt\={ } anions and extract their binding energies (BEs). Ramsauer-Townsend minima and shape resonances are also determined. The DCSs also yield the BEs of the Au\={ } and Pt\={ } anions [2]. The TCSs for the excited and ground Au\={ } and Pt\={ } anions are contrasted as well; they provide a clue to the significant catalytic properties of their nanoparticles. [1] D. Sokolovski \textit{et al}, Phys. Rev. A \textbf{76}, 012705 (2007); [2] Z. Felfli \textit{et al}, NIMB, At Press (2010). Supported by U.S. DOE, AFOSR and CAU CFNM, NSF-CREST Program [Preview Abstract] |
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E1.00173: Complex angular momentum investigation of excited lanthanide atoms: formation of negative ions A.Z. Msezane, Z. Felfli, D. Sokolovski The formation of stable excited lanthanide anions as Regge resonances is investigated in the electron impact energy region, E $<$ 1.0 eV using the recent Regge-pole methodology [1] wherein is embedded the electron-electron correlations together with a Thomas-Fermi type model potential that incorporates the vital core-polarization interaction. The near-threshold electron elastic total cross sections (TCSs) for the lanthanide atoms are found to be characterized by extremely narrow resonances whose energy positions are identified with the binding energies (BEs) of the resultant anions formed during the collision as Regge resonances. The extracted BEs for the excited lanthanide anions are contrasted with those of the most recently calculated electron affinities (ground state BEs) [2, 3]. Formation of bound excited anions is identified in the elastic TCSs of all the lanthanide atoms, except Eu and Gd. The imaginary part of the complex angular momentum L is used to distinguish between the shape resonances and the bound excited negative ions. [1] D. Sokolovski \textit{et al}, Phys. Rev. A \textbf{76}, 012705 (2007); [2] S.M. O' Malley and D. R. Beck, Phys. Rev. A \textbf{79}, 012511 (2009)~; [3] Z. Felfli \textit{et al}, Phys. Rev. A \textbf{79}, 012714 (2009) [Preview Abstract] |
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E1.00174: Electron affinity of small Pt clusters Zhifan Chen, Alfred Z. Msezane The adiabatic electron affinities (AEAs) and vertical EAs (VERs) for the small (2-5 atoms) platinum clusters have been evaluated in the density functional theory. The structures of clusters for the 2, 3, 4, and 5 Pt atoms were represented, respectively by linear, equilateral triangle, tetrahedron, and trigonal bipyramid atoms. The geometric optimization was performed using the DMol package under the generalized gradients approximation (GGA) with the Perdew-Wang exchange-correlation functional (PW91). Double numerical plus polarization has been used as the atomic basis sets to describe the valence electrons. All electrons in the core were treated explicitly with some relativistic effects. The AEAs for the clusters of 2,3,4, and 5 Pt atoms are respectively, 1.89, 1.67, 2.06 and 2.39 eV. The VEAs for the above clusters are respectively, 1.87, 1.62, 2.05, and 2.37 eV. The results show better agreement with the experiment than other similar calculations do. Our calculation demonstrates the importance of the correct structure and geometry optimization involving all the electrons. [Preview Abstract] |
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E1.00175: Electron-Impact Double Ionization of the Be Atom M.S. Pindzola, C.P. Ballance, J.A. Ludlow, F. Robicheaux, J. Colgan The time-dependent close-coupling (TDCC) and R-matrix with pseudo-states (RMPS) methods[1] are used to calculate the electron-impact double ionization cross section from the $1s^22s^2$ ground configuration of the Be atom. The TDCC calculations for the double ionization of the $2s^2$ subshell are carried out at incident energies ranging from 40 eV to 100 eV. The RMPS calculations are carried out from the threshold at 27.5 eV to 50 eV. The cross sections from the two non-perturbative methods are found to be in good agreement at 40 eV. Additional configuration-average distorted-wave calculations for the single ionization of the $1s^2$ subshell are carried out from the threshold at 124 eV to 500 eV. Subsequent autoionization of the $1s2s^2$ configuration of Be$^+$ leads to double ionization. The direct double ionization cross section is found to peak at 1.0 Mb around 70 eV, while the indirect double ionization cross section is found to peak at 2.0 Mb around 400 eV. \\[4pt] [1] D. C. Griffin and M. S. Pindzola, Adv. Atm. Mol. Opt. Phys. {\bf 54}, 203 (2006). [Preview Abstract] |
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E1.00176: Electron-impact excitation of O($^{1}$S) and O($^{1}$D) following dissociation of oxygen-containing molecules Wladek Kedzierski, Elly Blejdea, Amanda DiCarlo, William McConkey The well known oxygen green and red lines at wavelengths of 557.7, 630.0 and 636.4 nm result from transitions within the ground configuration of O and are dominant features of earth's aurorae. The parent O($^{1}$S and $^{1}$D) levels are metastable and are difficult to detect selectively in the laboratory. We have developed techniques and instrumentation involving solid rare gas (RG) matrices which are sensitive to these species through the formation of excited excimers (RGO*) which immediately radiate. The relative performance of different rare gas surfaces for O($^{1}$S) detection will be presented as functions of surface temperature (from 20-65K) and spectral output between 400 and 800 nm. Kr is shown to be the most sensitive to O($^{1}$S). First measurements of the production of O($^{1}$D) from N$_{2}$O and CO$_{2}$ targets will be presented. [Preview Abstract] |
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E1.00177: Excitation of VUV Atomic Sulphur Emissions following Electron-Sulphur Interactions Stephen Brotton, William McConkey A beam of sulphur, obtained by evaporation of solid sulphur, was crossed by an electron beam of carefully controlled energy and the resulting VUV radiation was detected, in a direction perpendicular to both beams, by a $\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $ meter Seya-Namioka monochromator with a CsI-coated channel electron multiplier detector. In an associated experiment a microwave discharge was used to dissociate the sulphur molecules released during evaporation. Relative calibration of the detection sensitivity over the wavelength range 90-170 nm was achieved using the well known spectrum of H$_{2}$ in this spectral region. Data, covering the electron-impact energy range from threshold to 350 eV, on the planetary-important multiplets at 142.5, 147.4 and 167.7 nm will be presented together with a full description of the experimental techniques, possible fragmentation channels etc. [Preview Abstract] |
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E1.00178: Vortices in (e,2e) momentum distributions J.H. Macek, S.Y. Ovchinnikov, J.B. Sternberg Complete experiments measure all variables associated with atomic processes. Momentum distributions of ejected electrons in pure states, as for (e,2e) measurements, are examples of such complete experiments. All structures seen in such distributions are listed by Briggs and co-workers\footnote{J. Berakdar and J. S. Briggs, J. Phys. B, {\bf 27}, 4271 (1994).} in 1994. Recently, we pointed out that there is a type of structure not included in the list. It has been shown that momentum distributions image time-dependent wave functions, and such wave functions may contain vortices owing to angular momentum transfer between species involved in the dynamical processes. The vortices are associated with exact zeros at single, isolated points. We have found such zeros in calculated momentum distributions for ion-atom collisions, photoionization, and (e,2e) distributions. By mapping distributions that image time-dependent wave functions we find velocity fields that circulate about exact zeros confirming their vortex structure. The vortices appear as unexpected holes in the (e,2e) momentum distributions. Our calculations suggest that one particular vortex has been observed.\footnote{A. J. Murray and F. H. Read, Phys. Rev. A, {\bf 47}, 3724 (1993).} [Preview Abstract] |
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E1.00179: Preliminary study of the bremsstrahlung spectrum produced from 25 keV electron bombardment of Ar gas atoms Jordan Watkins, Scott Williams We report on the preliminary results of experiments performed using a recently-constructed 25 keV electron accelerator. The intent of the study is to confirm whether or not there is any so-called polarizational bremsstrahlung contribution to the resultant radiation spectrum produced using Ar gas targets. [Preview Abstract] |
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E1.00180: Electron Impact Ionization of Helium Atom Hari P. Saha The recently extended MCHF method [1-2] of electron impact ionization of atoms will be applied to study the effects of electron correlation and polarization of the target in the initial state. The final state electron correlation between the two continuum electrons will be taken into account with the variationally determined screening potential [3-4]. The results of the triple differential cross section of helium atom will be presented for incident electron energies 26.6 and 28.6 eV . The screening potential approximation for the final state has been shown earlier [4] to agree very well with experiment and other accurate theory for the case when the two continuum electrons in the final state leave in the opposite direction. This indicates that effects of target correlation and polarization in the initial state are negligible. In the meeting we will present results of our calculation showing the effects of target correlation and polarization in the initial state on the triple differential cross section with and without the final state electron correlation for the case when $\theta _{12}$ = $\pi $ as well as other angles. The results will be compared with experimental and other available theoretical results. [1] H.P. Saha , Phys. Rev. A \textbf{77}, 062705 (2008), [2] H.P. Saha, J. Phys. B \textbf{41}, 55201 (2008), [3] M.R.H . Rudge and Seaton, Proc. R. Soc, London, Ser. A \textbf{283}, 262 (1965), [4] Cheng Pan and Anthony F. Starace, Phys. Rev. Lett. \textbf{67}, 185 (1991); Phys. Rev. A \textbf{45}, 4588 (1992). [Preview Abstract] |
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E1.00181: Electron-impact autoionization of helium in the presence of a laser field N.L.S. Martin, L. Ladino, B.A. deHarak We report experiments that examine the $2\ell2\ell'$ helium autoionizing levels excited by electron impact in the presence of an Nd:YAG laser field of 1.17~eV photons. The absorption or emission of a photon during the autoionization process is expected to produce one or more ``sidebands'' integral numbers of photon energies above and below a main autoionizing peak in the {\it ejected} electron energy spectrum. (In a free-free scatting experiment it is the {\it scattered} electron spectrum that acquires sidebands). The experiments are being carried out with a tailor-made data acquisition system that records events in a stream of 12.5ns wide time-bins either side of each laser pulse, and also the energies of the ejected electrons. We have observed significant differences in the the ``laser on'' and ``laser off'' energy spectra, but these differences do not seem to be merely sideband effects. We are currently continuing to collect data to improve the counting statistics and we will present our updated results. [Preview Abstract] |
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E1.00182: Electron-helium free-free scattering in the presence of a laser field B.A. deHarak, L. Ladino, N.L.S. Martin We report a series of experiments that examine electron-helium scattering in the presence of an Nd:YAG laser field of 1.17~eV photons. The goal of these experiments is to span the range of incident electron energies from 50~eV to 350~eV, and compare the results to the Kroll-Watson approximation\footnote{N. M. Kroll and K. M. Watson, Phys. Rev. A 8, 804 (1973)} (KWA) calculations. Effects of an intense laser field on the elastic scattering of electrons from argon were first reported by Andrick in 1976\footnote{D. Andrick and L. Langhans, J. Phys. B 9, L459 (1976)}. In general, KWA calculations have been adequate to describe experimental results where the photon energy is significantly less than the incident electron energy -- a major exception being the case of small scattering angles where large discrepencies have been noted\footnote{e.g., B. Wallbank and J. K. Holmes, Phys. Rev. A 48, R2515 (1973)}. Our experiments test the KWA over a range of electron incident energies that has not been previously investigated. [Preview Abstract] |
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E1.00183: POST-DEADLINE POSTERS |
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E1.00184: Laser Cooling of Buffer Gas Beams Julia Rasmussen, Hsin-I Lu, Dave Patterson, John Doyle We realize a continuous, collimated and cold atomic beam with buffer gas and laser cooling. Atoms from an oven (450K) are mixed with cold neon buffer gas (15K) and emitted in a cold, high flux beam. Further collimation produces a cold rubidium beam with a flux of $3 \times 10^{10}$ atoms per second and a longitudinal temperature of 1.5 K. We demonstrate transverse laser cooling and spatial separation of rubidium from buffer gas by laser deflection. An intrinsically low longitudinal temperature makes such a continuous beam source ideal for cold collision studies. An atomic beam with low background buffer gas is also suitable for trap loading. We believe this source may be generalized to other atoms and molecules with a significant vapor pressure below 1000 K. [Preview Abstract] |
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E1.00185: Improving system for achieving ultra cold atoms Wanhee Lee, Dahyun Yum, Jina Park, Wonho Jhe We are studying on building ultra cold atoms. But we had lots of problems. So we were trying to solve those things. Some are very important and the other seems to minor but huge affects on the system. We change the time control system since each step was so random that makes impossible to analysis some properties by time of flight method (TOF). And the things giving effects to the fields we use were removed. By these processes, we extended the lifetime of atomic cloud in the magnetic trap. After optical pumping to F=1 state, we loaded more atoms into the magnetic potential. And we employ the time-averaged orbiting potential (TOP) trap applied by the superposition of a big spherical quadrupole field and a small rotating bias field at 7kHz. In each step, we check the temperature and the density obtained by distribution of trapped atoms. In this poster, I will describe how to modify and show some results. [Preview Abstract] |
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E1.00186: Using the sudden expansion as a cooling scheme for interacting fermions in optical lattices Fabian Heidrich-Meisner, Salvatore Manmana, Marcos Rigol, Alejandro Muramatsu, Adrian Feiguin, Elbio Dagotto Time-dependent phenomena in ultracold atomic gases are currently attracting a lot of attention, as such phenomena give insights into nonequilibrium properties of interacting particles. We analyze the example of the sudden expansion of fermions in an optical lattice [1]. Our main focus is on the case in which the initial state has a strong admixture of double occupancies. We promote the notion of quantum distillation: during the expansion, and in the presence of strongly repulsive interactions, doublons group together, forming a nearly ideal band insulator, which is metastable with a low entropy. Our analysis employs the density matrix renormalization method, and we present results for experimentally observable quantities such as the radius of the particle cloud. We suggest that the quantum distillation effect could be used for cooling purposes in experiments with two-component Fermi gases [2].\\ \noindent [1] Heidrich-Meisner et al., Phys. Rev. A 78, 013620 (2008)\\ \noindent [2] Heidrich-Meisner et al., Phys. Rev. A 80, 041603(R) (2009) [Preview Abstract] |
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E1.00187: Experimental problems related with ultra cold atoms Jina Park, Dahyun Yum, Wanhee Lee, Wonho Jhe We have been trying to obtain ultra cold atoms. We always faced some troubles. Part of the things were solved. (see Wanhee Lee's poster) But it still exists that stop our research from going further. In this poster, I will show the problems that we have. And I will also deal with the experimental setup related with our future research. We are using time orbiting potential (TOP) trap. So we are interest in studying the motion of cold atoms on the optical lattice confined by TOP potential. [Preview Abstract] |
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E1.00188: Effective Methodology of Quantum Dot Infrared Photodetectors through VisSim Mohamed El Tokhy, Imbaby Mahmoud, Hussien Konber Our goal in this paper is to evaluate the performance of quantum dot infrared photodetectors (QDIPs). The tools that we are used are the VisSim technique along with the block diagram programming procedures. The benefits of using this modeling language are the simplicity of carrying out the performance's measurement through computer simulation instead of setting up a practical procedure which becomes expensive as well as the difficulty of its management. The roles that the parameters of fabrication can play in the characteristics of QDIPs are discussed through developed models implemented by VisSim environment. In order to confirm our models and their validity on the practical applications, we make a comparison between the results obtained by our models and that experimentally published and full agreement is observed. Implicit solution of QDIPs governing by dynamic equations provides exact handling of the device performance. As an example, dark current, photocurrent, responsivity and detectivity is investigated. The implemented models can help designers and scientists to optimize their devices to meet their requirements. [Preview Abstract] |
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E1.00189: Viscosity and mutual diffusion of deuterium-tritium mixtures in the warm dense matter regime James S. Cohen, D.A. Horner, F. Lambert, J.D. Kress, L.A. Collins Viscosity and mutual diffusion in the deuterium-tritium (DT) mixture are important input properties for modeling inertial-confinement plasmas. We have calculated viscosity and mutual diffusion of DT in the pertinent warm, dense matter regime for densities from 5 to 20 g/cm$^3$ and temperatures from 2 to 10 eV, using both finite-temperature density-functional theory molecular dynamics (QMD) and orbital-free molecular dynamics (OFMD). QMD treats the electrons quantum mechanically through finite-temperature density-functional theory. OFMD treats the kinetic energy of the electrons semiclassically. Both treat the nuclei classically. These two treatments are in generally good agreement. Comparisons are also made with simple models, esp.the one-component plasma (OCP) model. The reduced diffusion and viscosity coefficients are found to depend largely, though not completely, only on the Coulomb coupling parameter $\Gamma$ (the ratio of potential energy to kinetic energy), with a minimum in the reduced viscosity at $\Gamma \approx 25$, approximately the same position found in the OCP simulations. [Preview Abstract] |
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E1.00190: Resolving remaining discrepancies between H$_{3}^{+}$ recombination cross sections obtained by ion storage rings, plasma afterglow experiments, and theory Rainer Johnsen While theoretical Jahn-Teller calculations of the dissociative recombination of H$_{3}^{+}$ ions with electrons agree well with the binary rate coefficients obtained in ion storage rings, some plasma afterglow measurements have consistently yielded either much lower (by factors of 10 or more) or higher values (by factors of 3 to 4). The origin of these disturbing discrepancies has not been clearly identified. I will show that the very low values obtained in afterglows at low concentrations of neutral hydrogen simply reflect recombination of ion species other than H$_{3}^{+}$, rather than being due to H$_{2}$-assisted recombination, different spin modifications, or vibrational excitation of H$_{3}^{+}$, as has been suggested. Also, the mechanisms that have been proposed to account for the apparent recombination enhancement due to neutral atoms (helium in particular) are not convincing. I will show here that a modified form of ``collisional dissociative recombination'' can account for the observed faster recombination rates in plasma experiments at high helium densities. In this model, the enhancement of the recombination results from three-body electron capture into Rydberg states of high angular momentum $l$, followed by $l$-reducing collisions with neutral atoms that induce predissociation. I conclude that there is no true ``discrepancy'' between afterglow and storage ring H$_{3}^{+}$ recombination coefficients [Preview Abstract] |
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E1.00191: Recombination Reactions in the Thermal Decomposition of Anisole: An Investigation of Benzene and Naphthalene Formation Adam Scheer, Barney Ellison, Calvin Mukarakate, David Robichaud, Mark Nimlos Thermal decompositions of anisole (C$_{6}$H$_{5}$OCH$_{3})$ and methyl-deuterated anisole (C$_{6}$H$_{5}$OCD$_{3})$ are studied using a hyperthermal tubular reactor and photoionization reflectron time-of-flight mass spectrometer. Gas exiting the reactor is subject to a supersonic expansion after a residence time of 65 $\mu$s, allowing detection of highly chemically reactive radical species. Anisole decomposes through loss of a methyl group ({\textbullet}CH$_{3})$ to form phenoxy radical (C$_{6}$H$_{5}$O{\textbullet}), followed by ejection of a CO to form cyclopentadienyl radical (c-C$_{5}$H$_{5}$; CPDR). Benzene is generated primarily by thermal decomposition of methylcyclopentadiene (C$_{5}$H$_{5}$CH$_{3}$; MCPD). The MCPD results from methyl radical recombination with CPDR. The MCPD then undergoes two hydrogen atom losses and a ring expansion resulting in benzene. At T$_{wall}$ = 1200 \r{ }C -- 1300 \r{ }C a large amount of propargyl radical (CH$_{2}$CCH) is observed. Propargyl radical recombination accounts for a small fraction of the observed benzene. Naphthalene and its precursor intermediates (C$_{10}$H$_{10}$, C$_{10}$H$_{9})$, resulting from CPDR recombination, are also observed. The presence of benzene and naphthalene is confirmed with resonance-enhanced multiphoton ionization (REMPI). [Preview Abstract] |
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E1.00192: Signatures of symmetry and electronic structure in high harmonic generation in polyatomic molecules Michael Wong, Jean-Paul Brichta, Ravi Bhardwaj We report detailed measurements of high harmonic generation in chloromethane molecules (CCl$_{4}$, CHCl$_{3}$, and CH$_{2}$Cl$_{2})$ to show that fingerprints of symmetry and electronic structure can be decoded from high harmonic generation even in complex randomly oriented molecules. In our measurements, orbital symmetries of these molecules are reflected as both extended harmonic cut-offs and a local minimum in the ellipticity dependence of the cut-off harmonics, suggesting occurrence of quantum interferences during ionization. The harmonic spectra exhibit two distinct interference minima at $\sim $42 eV and $\sim $60 eV. We attribute the former to the Cooper minimum in the photoionization cross-section and the latter to the intra-molecular interference during the recombination process. [Preview Abstract] |
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E1.00193: Relative number squeezing by atomic four-wave mixing Jean-Christophe Jaskula, Valentina Krachmalnicoff, Marie Bonneau, Guthrie Partridge, Denis Boiron, Alain Aspect, Christoph Westbrook A collision between two Bose-Einstein condensates (BEC) can formally be seen as an atomic four-wave mixing process, equivalent to parametric down conversion (PDC) in quantum optics. In this poster, we report the realization and observation of such a collision. By using a 3D position sensitive single atom detector, we are able to measure the time of flight momentum distribution of the atoms that are scattered from the BEC by s-wave interactions, and find that these atoms lie on a halo. Contrary to an ideal s-wave scattering distribution, however, we find that the scattered halo is not uniform and spherical, but instead has an angle dependent thickness and radius. In addition, by considering opposing regions of the halo, we observe relative number squeezing whereas relative atom number distributions between non-opposing regions show a poissonnian behaviour. Sub-poissonnian distributions have previously been measured in PDC experiments when non-classical states of light such as squeezed and entangled states were studied. This observation suggests that a collision between two BECs is a potentially good candidate as a source of entangled atoms. [Preview Abstract] |
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E1.00194: Visual Analysis of DFT Functionals K.M. Flurchick, Patrick McCarter In this work, various functionals for Density Functional Theory calculations are investigated. The computed electron density, molecular geometry and other properties are compared to experimental and CCSD(T) calculations to determine the effectiveness of each functional. In this work, the electron density differences between each functional, the CCSD(T) results and experimental values are analyzed both visually and numerically. Small carbon based molecules are used to study the different functionals including single, double and triple bonds. The properties considered in this work include the geometry, energies, ionization potential and gradients of the electron density. [Preview Abstract] |
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E1.00195: High Temperature Measurement of Quantum Viscosity in a Strongly Interacting Fermi Gas Chenglin Cao, Ethan Elliott, James Joseph, Jessie Petricka, Haibin Wu, John Thomas We determine the quantum viscosity of a strongly interacting Fermi gas in the high temperature regime using precision measurements of the expansion dynamics. Our results demonstrate that the magnitude and temperature scaling are in very good agreement with recent theoretical predictions. This work paves the way for quantum viscosity measurements in the low temperature regime where a strongly interacting Fermi gas is believed to be a nearly perfect fluid. [Preview Abstract] |
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E1.00196: Novel Feshbach resonances in a $^{40}$K spin-mixture J.T.M. Walraven, A. Ludewig, T.G. Tiecke We present experimental results on novel s-wave Feshbach resonances in $^{40}$K spin-mixtures. Using an extended version of the Asymptotic Bound-state Model (ABM) [1] we predict Feshbach resonances with more promising characteristics than the commonly used resonances in the ($\vert $F,m$_{F}>) \quad \vert $9/2,-9/2$>+\vert $9/2,-7/2$>$ and $\vert $9/2,-9/2$>+\vert $9/2,-5/2$>$ spin mixtures. We report on an s-wave resonance in the $\vert $9/2,-5/2$>+\vert $9/2,-3/2$>$ mixture. We have experimentally observed the corresponding loss-feature at B$_{0}\sim $178 G with a width of $\sim $10G. This resonance is promising due to its large predicted width and the absence of an overlapping p-wave resonance. We present our recent results on measurements of the resonance width and the stability of the system around this and other observed s-wave and p-wave resonances. \\[4pt] [1] T.G. Tiecke, et al., Phys. Rev. Lett. 104, 053202 (2010). [Preview Abstract] |
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E1.00197: Ion Motion Stability in Asymmetric Surface Electrode Ion Traps Fayaz Shaikh, Arkadas Ozakin Many recently developed designs of the surface electrode ion traps for quantum information processing have asymmetry built into their geometries. The asymmetry helps rotate the trap axes to angles with respect to electrode surface that facilitate laser cooling of ions but introduces a relative angle between the RF and DC fields and invalidates the classical stability analysis of the symmetric case for which the equations of motion are decoupled. For asymmetric case the classical motion of a single ion is given by a coupled, multi-dimensional version of Mathieu's equation. In this poster we discuss the stability diagram of asymmetric surface traps by performing an approximate multiple scale perturbation analysis of the coupled Mathieu equations, and validate the results with numerical simulations. After obtaining the stability diagram for the linear fields, we simulate the motion of an ion in a given asymmetric surface trap, utilizing a method-of-moments calculation of the electrode fields. We obtain the stability diagram and compare it with the ideal case to find the region of validity. Finally, we compare the results of our stability analysis to experiments conducted on a microfabricated asymmetric surface trap. [Preview Abstract] |
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E1.00198: Even-parity resonances with synchrotron radiation from Laser Excited Lithium at 1s$^2$2p State Ming-Tie Huang, Ralf Wehlitz Correlated many-body dynamics is still one of the unsolved fundamental problems in physics. Such correlation effects can be most clearly studied in processes involving single atoms for their simplicity.Lithium, being the simplest open shell atom, has been under a lot of study. Most of the studies focused on ground state lithium. However, only odd parity resonances can be populated through single photon (synchrotron radiation) absorption from ground state lithium (1s$^2$2s). Lithium atoms, after being laser excited to the 1s$^2$2p state, allow the study of even parity resonances. We have measured some of the even parity resonances of lithium for resonant energies below 64 eV. A single-mode diode laser is used to excite lithium from 1s$^2$2s ground state to 1s$^2$2p ($^2$P$_{3/2}$) state. Photoions resulting from the interaction between the excited lithium and synchrotron radiation were analyzed and collected by an ion time-of-flight (TOF) spectrometer with a Z- stack channel plate detector. The Li$^+$ ion yield was recorded while scanning the undulator along with the monochromator. The energy scans have been analyzed regarding resonance energies and parameters of the Fano profiles. Our results for the observed resonances will be presented. [Preview Abstract] |
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E1.00199: A study of long-range covalent--ion-pair coupling in Rb$_2$ and a comparison with Li$_2$ Jeffrey Philippson, Robert Collister, Ralph Shiell The formation of bound ion-pair states through optical excitation at short-range has been observed in a number of alkali dimers, while the corresponding process due to collisions following excitation at long-range has thus far only been observed between alkali atoms and large molecules of exceptionally high electron affinity [1]. A study of long-range covalent--ion-pair coupling in cold Rb$_2$ and Li$_2$ is presented, including the dependence of this long-range process on parameters such as the initial relative velocity and impact parameter for two different mechanisms [2]. Calculations are based on the well-known Landau--Zener formalism and particular attention has been paid to the regions of parameter space in which the approximations implicit in this approach remain valid. Cross-sections for ion-pair formation are calculated for different channels of the ground- and excited-state atom pair in order to identify possible ``gateway'' states for efficient experimental production of bound ion-pair systems.\\[4pt] [1] M. Cannon and F.B. Dunning, J. Chem. Phys. {\bf 130} 044304 (2009)\\[0pt] [2] M. Cheret and L. Barbier, Phys. Rev. A {\bf 30} 1132 (1984). [Preview Abstract] |
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