Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session K1: Poster Session II (4:00 pm - 6:00 pm) |
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Room: Royal Ballroom |
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K1.00001: ATOMIC AND MOLECULAR STRUCTURE AND PROPERTIES II |
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K1.00002: Every Molecule, When Created, Will Exhibit No Motion or Linear, Vibratory and or Rotational Motion Which May Later Be Altered By External Forces : A Natural Law Stewart Brekke All bodies have no motion, or linear, vibrational and/or rotational motion. Therefore, when a molecule is created, it will exibit some or all of these properties due to the excess energy of creation if present. The energy equation for the newly created molecule is $E=m_0c^2 + 1/2m_0v^2 + 1/2I\omega^2 + 1/2kx_0^2,$ where $1/2m_0v^2$ is the linear kinetic energy if present, $1/2I\omega^2$ is the rotational kinetic energy if present and $1/2kx_0^2$ is the vibrational kinetic energy of the the molecule if present. [Preview Abstract] |
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K1.00003: Ion-Pair States in Ungerade Molecular Hydrogen Elizabeth McCormack The results of an investigation of long-range ungerade states of molecular hydrogen are reported. Resonantly enhanced multi-photon ionization via the E,F 1?+g , v = 6, J = 0, 1, and 2 states is used to probe the energy region above the H(1s) + H(3l) dissociation threshold. Both molecular and atomic ion production are detected as a function of wavelength by using a time-of-flight mass spectrometer. A series of resonances is observed with energies that agree with the predictions of a mass-scaled Rydberg formula for bound states of the H+H- ion pair. Measured quantum defects, rotational dependencies, and line widths are reported. The observed spectra are compared to recent theoretical predictions for the series, which include line widths that oscillate in magnitude with energy and perturbations with several interloping resonances corresponding to vibrational states trapped inside the barriers of the 5 and 6 1?+u potential-energy curves [1].\\[4pt] [1] A. Kirrander and Ch. Jungen, Phys. Rev. A. 84, 052512 (2011). [Preview Abstract] |
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K1.00004: S-matrix calculations of energy levels of the lithium isoelectronic sequence J. Sapirstein, K.T. Cheng A QED approach to the calculation of the spectra of the lithium isoelectronic sequence is implemented. A modified Furry representation based on the Kohn-Sham potential is used to evaluate all one- and two-photon diagrams with the exception of the two-loop Lamb shift. Three-photon diagrams are estimated with Hamiltonian methods. After incorporating recent calculations of the two-loop Lamb shift and recoil corrections a comprehensive tabulation of the $2s$, $2p_{1/2}$ and $2p_{3/2}$ energy levels as well as the $2s-2p_{1/2}$ and $2s-2p_{3/2}$ transition energies for $Z=10-100$ is presented. [Preview Abstract] |
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K1.00005: Relativistic Configuration Interaction Lifetimes and Transition Probabilities for W II Donald R. Beck, Marwa H. Abdalmoneam Lifetimes of the lowest 13, 30, 38, 40, and 35 levels of 2J=1, 3, 5, 7 and 9, respectively, odd parity have been computed. Comparisons with measured values\footnote{H. Nilsson et al, Eur. Phys. J. D49, 13 (2008) and references therein.} indicate improved agreement as compared with the semi-empirical values.\footnote{Ibid.} With the inclusion of the FOTOS selected\footnote{D. R. Beck, Phys. Scr. 71,447 (2005) for RCI methodology.} 5p$\rightarrow$5d excitations, agreement between the velocity and length gauges is good. Small shifts are introduced for some nearby levels to represent the missing correlation effects, and it is shown that the sum of 1/tau and Lande g-values are nearly conserved as calculation proceeds for such levels. [Preview Abstract] |
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K1.00006: Random and modulated noise spectroscopy in a Lambda system Pengxiong Li, Lei Feng, Liang Jiang, Yanhong Xiao Lasers have inherent phase noise, which can be converted to amplitude noise after atom-light interaction. Previously, such PM-AM conversion has been extensively studied in a two-level system. The three-level Lambda system has attracted much attention in recent years due to its relevance to quantum memory, magnetometers and atomic clocks. We investigate PM-AM in this system with both random phase noise and modulated phase ``noise''. Atomic dynamics from both ground and excited states can be revealed from the output intensity noise spectrum. Responses of the system to noise show resonance behavior distinct from a two-level system. For the modulated noise case, adiabatic and nonadiabatic regimes were identified. In particular, using the intensity cross-correlation of the two optical fields as an observable leads to subnatural spectrum for the transition between the two ground states. We will present experimental and theoretical results. [Preview Abstract] |
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K1.00007: ABSTRACT WITHDRAWN |
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K1.00008: Improved characterization of the A-state of lead monofluoride and measurement of its dipole moment James Coker, Tao Zh. Yang, John E. Furneaux, Neil E. Shafer-Ray Lead monofluoride (PbF) is an attractive candidate for measurement of the electric dipole moment of the electron (eEDM) because of its small $g$-factor and its large enhancement factor [1]. In order to measure the eEDM with PbF, broad and accurate knowledge of its spectroscopic constants is needed. Although the ground (X$_1$) state constants are known to 100 kHz precision [2], the excited states have not been as precisely characterized. A promising state for hyperfine optical detection of the X$_1$ state is the A state [3]. Using a time-of-flight detection scheme described in the work, we present new spectroscopic data of isolated $^{208}$Pb$^{19}$F. The analysis of which yields constants of the A state and molecular dipole moments of the X$_1$ and A states to new precision.\\[4pt] [1] N.~Shafer-Ray, Phys. Rev. A {\bf 73}, 034102 (2006).\\[0pt] [2] R.~J. Mawhorter et~al., Phys. Rev. A {\bf 84}, 022508 (2011).\\[0pt] [3] C.~P. McRaven, P.~Sivakumar, N.~E. Shafer-Ray, G.~E. Hall, and T.~J. Sears, J. Mol. Spec. {\bf 262}, 89 (2010). [Preview Abstract] |
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K1.00009: Advances in experimental spectroscopy of Z-pinch plasmas and applications V.L. Kantsyrev, A.S. Safronova, U.I. Safronova, I. Shrestha, M.E. Weller, G.C. Osborne, V.V. Shlyaptseva, P.G. Wilcox, A. Stafford Recent advances in experimental work on plasma spectroscopy of Z-pinches are presented. The results of experiments on the 1.7 MA Z-pinch Zebra generator at UNR with wire arrays of various configurations and X-pinches are overviewed. A full x-ray and EUV diagnostic set for detailed spatial and temporal monitoring of such plasmas together with theoretical support from relativistic atomic structure and non-LTE kinetic codes used in the analysis are discussed. The use of a variety of wire materials in a broad range from Al to W provided an excellent opportunity to observe and study specific atomic and plasma spectroscopy features. In addition, the applications of such features to fusion and astrophysics will be considered. [Preview Abstract] |
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K1.00010: Energy levels and radiative rates for transitions in Ti VI Kanti Aggarwal, Francis Keenan, Alfred Z. Msezane Energies for 568 levels among the n=3+$3p^{6}4l$+3s3p$^{5}$4$l$ configurations of Ti VI are calculated using the GRASP (General-purpose Relativistic Atomic Structure Program) code, which is based on the multi-configuration Dirac-Fock (MCDF) method. Additionally, radiative rates are calculated for all types of transitions, namely electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2). Lifetimes are also calculated for all the levels and extensive comparisons are made with the earlier available data as well as with other parallel calculations from the FAC (Flexible Atomic Code). Discrepancies for several levels with the earlier calculations of Mohan et al, (ADNDT 93 105 (2007)) are highlighted. [Preview Abstract] |
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K1.00011: The calculation of generalized oscillator strength densities of Argon by using an eigenchannel R-matrix method X. Gao, J.M. Li Understanding the detailed dynamics of electron-ion interactions is of fundamental importance to various plasma applications in the fields of astrophysics, fusion energy researches and so on. Theoretical computations should play indispensable role to satisfy needs. Using our modified R-matrix code R-Eigen, we can directly calculate the short-range scattering matrices with good analytical properties in the whole energy regions, from which we can obtain all energy levels and the related scattering cross sections with accuracies comparable with spectroscopic precision. With the corresponding high-quality eigenchannel wavefunctions, various transition matrix elements can be readily calculated, such as the generalized oscillator strength densities (GOSD). The GOSD is directly related with the high-energy electron impact excitation cross sections. In eigenchannel representation, the GOSD curves of the excited states in an eigenchannel form a surface, which is a smooth function of the momentum transfers and the excitation energies. From such smooth GOSDs, we can obtain the generalized oscillator strength of any specific excited state through multichannel quantum defect theory, e.g. infinite Rydberg(including strongly perturbed one), autoionization and continuum states. As an example, we will present our recent calculation results of Ar, which are in good agreement with available benchmark experiments. [Preview Abstract] |
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K1.00012: PHOTON INTERACTIONS WITH ATOMS, IONS, AND MOLECULES II |
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K1.00013: Analytic Description of Laser Assisted Electron Scattering Plateau Spectra for Elliptical Polarization Alexander V. Flegel, Mikhail V. Frolov, Nikolai L. Manakov, Anthony F. Starace We present an analytic description of laser-assisted electron scattering (LAES) for the case of an elliptically polarized laser field. A closed-form analytic formula describing plateau features in LAES is derived quantum mechanically in the low-frequency limit. This formula provides an analytic explanation for the oscillatory patterns of LAES cross sections in the high-energy part of the LAES spectra. This formula generalizes the result for a linearly polarized laser field presented in [1] to the case of elliptical polarization and confirms the possibility of factorizing the LAES cross section into the product of two atomic factors involving the field-free cross sections for elastic electron-atom scattering and a factor (insensitive to atomic parameters) describing the elliptically polarized laser-driven motion of the electron. These results provide a fully quantum justification of the classical rescattering scenario for LAES in an elliptically polarized laser field.\\ [4pt] [1] A.\,V. Flegel {\it at al.} J. Phys. B \textbf{42}, 241002 (2009). [Preview Abstract] |
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K1.00014: Stimulated cooling of molecules on multiple rovibrational transitions with coherent pulse trains Ekaterina Ilinova, Jonathan D. Weinstein, Andrei Derevianko We propose a method of stimulated laser cooling of diatomic molecules by counter-propagating $\pi$-trains of ultrashort laser pulses. The cooling cycles occur on the rovibrational transitions inside the same ground electronic manifold, thus avoiding the common problem of radiative branching in Doppler cooling of molecules. By matching the frequency comb spectrum of the pulse trains to spectrum of the R-branch rovibrational transitions we show that stimulated cooling can be carried out on several rovibrational transitions simultaneously, thereby increasing number of cooled molecules. The exerted optical force does not rely on the decay rates in a system and can be orders of magnitude larger than the typical values of scattering force obtained in conventional Doppler laser cooling schemes. http://arxiv.org/pdf/1201.1015.pdf [Preview Abstract] |
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K1.00015: Angular distributions for the triple photoionization of lithium James Colgan, Michael Pindzola The time-dependent close-coupling method is used to calculate angular distributions for the triple photoionization of lithium [1]. The angular distributions reveal the preferred break-up patterns for the four-body Coulomb problem. We find that the angular distributions near the peak of the total triple photoionization cross section at 300 eV are complex, with more than one major break-up pattern evident. Further calculations are underway at smaller photon energies nearer the triple ionization threshold and will be reported at the conference. \\[4pt] [1] J. Colgan and M. S. Pindzola, Phys. Rev. Letts, in press (2012). [Preview Abstract] |
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K1.00016: Efficient Collection of Single Photons Emitted from a Trapped Ion into a Single Mode Fiber for Scalable Quantum Information Processing Andre Van Rynbach, Rachel Noek, Taehyun Kim, Peter Maunz, Jungsang Kim Interference and coincidence detection of two photons emitted by two remote ions can lead to an entangled state between the ions, which is a critical resource for scalable quantum information processing [1]. The success probability of entanglement generation in current experimental realizations is mainly limited by the low coupling efficiency of a photon emitted by an ion into a single mode fiber. Here we consider two strategies to enhance the collection probability and entanglement generation rate of photons emitted from trapped Yb$^{+}$ ions. The first method uses high numerical aperture optics to enhance light collection, where a practical collection probability of over 10{\%} is possible with proper control of aberration. The second method uses a hemispherical optical cavity created between a flat mirror containing a surface trap and a spherical mirror to enhance the spontaneous emission into the cavity mode. We show that fiber coupling efficiency of over 30{\%} is possible using this approach, leading to an improvement in the entanglement generation rate of over four orders of magnitude. We also report on experimental progress towards realizing these two light collection schemes using surface trapped Yb$^{+}$ ions. \\[4pt] [1] P. Maunz et al. Phys. Rev. Lett. 102, 250502-4 (2009). [Preview Abstract] |
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K1.00017: Investigating the Possibility of Overcoming Photon Loss via Photon-Phonon Interactions Bhaskar Roy Bardhan, Jonathan Dowling In optical quantum information processing, photons are usually routed through optical fibers or waveguides. However, absorption of the photons in the fiber during the transmission introduces errors in the information processing. We model the absorption of photons with the creation of vibrational excitation (phonon) in one of the modes of the fiber, and investigate how the decay rate can be modified with various density of phononic modes and fluctuations in the fiber. Decoherence effects are studied in terms of the spectral density of the bath and the resulting decoherence function. Moreover, we analyze the effects of Markovian and non-Markovian environments on the absorption rate and see if well-known open-loop control techniques such as dynamical decoupling can be used, under suitable approximations, to overcome the losses due to the photon absorption. [Preview Abstract] |
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K1.00018: Towards understanding thermodynamics and energy transport in strings of trapped ions Michael Ramm, Thaned Pruttivarasin, Ishan Talukdar, Hartmut Haeffner We report experiments on laser induced heating of ions confined in a linear Paul trap. Specifically, we investigate the mechanism of melting of a crystallized ion chain due to heating by light detuned blue from an atomic resonance. In these experiments, we observe the decay of ion fluorescence as we shine laser light on either the entire ion string or a small subset. From these measurements we hope to extract information on the thermodynamic properties of such Coulomb crystals. Understanding these properties, together with the ability to address individual ions will facilitate the study of excitation transfer dynamics along the chain. [Preview Abstract] |
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K1.00019: STIRAP Production of Rydberg Helium: Effects of Thermal Radiation and Level Multiplicity Petr M. Anisimov, Yuan Sun, Harold Metcalf Stimulated Raman Adiabatic Passage (STIRAP) has been used in a series of experiments to excite Helium atoms to Rydberg states starting from the metastable $2 ^3 $S state. The usual picture of STIRAP in a three level system suggests that experimental efficiency should be nearly 100\%, but our measured efficiency was limited to less than 70\%. Here we report a detailed model of the STIRAP process in metastable Helium that accounts for the multilevel structure of the transition and effects of thermal radiation that lead to ionization as well as population redistribution among Rydberg states. [Preview Abstract] |
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K1.00020: Photoionization of free and confined Mg : Evolution of the cross section with depth of the confining well P. Padukka, H.-L. Zhou, S.T. Manson The photoionization cross sections of the outer $3s^2$ shell of free and confined Mg have been calculated. The $C_{60}$ confinement is modeled as an attractive spherical potential of inner radius 5.8 a.u., thickness of 1.89 a.u. and a depth U$_0$ varying from 0.0 to 0.302 a.u. (corresponding to Mg@$C_{60}$). Modified MCHF and HF codes have been used to obtain the single and multi-configuration wave functions, which were calculated self-consistently including the extra confining potential. The photoionization cross sections were calculated using the R-matrix method at both the LS coupling and Breit-Pauli (BP) approximation level. We found that the ionization energy of the Mg ground state increases somewhat with increasing well depth. Moreover the photoionization cross section of free Mg, which is dominated in the threshold region by doubly-excited $nln^{\prime}l^{\prime}$ resonances, changes dramatically in the presence of the confining well; partially because many of the near-threshold resonances move below threshold with increasing well depth. In addition the BP calculation shows spin-orbit splitting, significant even at such low Z. [Preview Abstract] |
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K1.00021: Attosecond streaking of correlated two-electron transitions Renate Pazourek, Stefan Nagele, Johannes Feist, Joachim Burgd\"orfer Attosecond streaking is one of the most fundamental processes in attosecond science allowing for a mapping of temporal information to the energy domain. For the measurement of the release time of electrons in atomic photoemission a time-resolution on the sub-100 attosecond time scale could be achieved [Science 328, 1658 (2010)]. The measured time shifts contain timing (or spectral phase) information associated with the Eisenbud-Wigner-Smith (EWS) time delay. Considerable additional time shifts caused by the probing infrared field could be identified on the single-particle level. In this contribution we adress the role of electron correlation in the streaking process. We study two-electron systems for which we solve the full time-dependent Schr\"odinger equation. For final ionic states with small polarizability correlation effects beyond those of the one-photon transition already included in the EWS time delay are absent. However, for shake-up ionization we find an additional streaking time shift due to the correlated dynamics of the dressed bound electron and the streaked continuum electron. [Preview Abstract] |
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K1.00022: Variation of Structure Profile for Narrow Resonances in Atomic Photoabsorption as Function of Column Density T.N. Chang, T.K. Fang We present in detail the variation of the structure profiles for narrow doubly excited resonances in atomic photoabsorption at finite temperature as functions of column density of the target atom systems. In particular, we will examine the change in the peck cross sections, the effective full width at half maximum (FWHM) and the effective asymmetry parameter of the theoretically simulated resonance structure as the pressure varies [1]. We will also examine the temperature effects on the structure profile as the pressure varies. \\[4pt] [1] J. I. Lo et al, PRA 82, 012504 (2010). [Preview Abstract] |
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K1.00023: Inner-shell photodetachment from O$^{-}$ N.D. Gibson, C.W. Walter, D.J. Matyas, A.N. Lebovitz, Y.-G. Li, R.M. Alton, S.E. Lou, R.C. Bilodeau, N. Berrah, A. Aguilar, D. Hanstorp The K-shell photodetachment spectrum of O$^{-}$ has been investigated using the merged ion-photon beam photodetachment technique. O$^{-}$ ions were produced in a Cs sputtered negative ion source (SNICS II) on a Movable Ion Photon Beamline while the photons were produced by the undulator on the Advanced Light Source Beamline 8.0.1. Positive oxygen ions formed by multiple detachment were detected as a function of photon energy. Photoexcitation of a $1s$ electron leads to a short-lived Feshbach resonance $\sim$3 eV below the 1s detachment threshold due to the extra stability of the now full $2p^{6}$ shell [1]. Energy calibration of the incoming photons, using an inline gas cell, leads to precise energy level assignments for the observed states. The Feshbach resonance is observed near 525 eV in the O$^{+}$, O$^{2+}$ and O$^{3+}$ channels. Comparisons to inner-shell photoionization of O will be discussed for both experiment [2] and theory [3]. \\[4pt] [1] Bilodeau RC, \itshape{et al.}\normalfont, Phys. Rev. A, \bfseries72\normalfont, 050701(R), 2005.\\[0pt] [2] Stolte WC, \itshape{et al.}\normalfont, J. Phys. B, \bfseries30\normalfont, 4489, 1997.\\[0pt] [3] Gorczyca TW, McLaughlin BM, J. Phys. B, \bfseries33\normalfont, L859, 2000. [Preview Abstract] |
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K1.00024: Photodissociation and Predissociation of Heavy Molecular Ions Svetlana Kotochigova, Alexander Petrov In support of experimental efforts to sympathetically cool heavy BaCl$^+$ molecular ions we investigated a detection mechanism of these ions by developing a quantum mechanical model of photodissociation and predissociation to ionic Ba$^+$ and neutral Cl atoms. Photodissociation occurs when the absorption of a photon leads to a transition from the ground electronic state to a repulsive inner wall of an excited potential. Alternatively, photon absorption leads to a transition to a bound state of an excited state followed by predissociation into a third electronic state. We first calculated the ground X and excited A and B potentials and transition dipole moments of the BaCl$^+$ molecule, using CASPT2 method. We then evaluated matrix elements of the dipole moment operator between the initial rovibrational states $vJM$ of the X potential and final scattering states in the repulsive A potential. The photodissociation cross-section is proportional to the square of these matrix elements. We assumed a thermal distribution over rovibrational states of the X potential in order to compare with available experimental data. We then used a coupled channel calculation that involved the B and and A excited electronic states coupled by a coriolis interaction to obtain predissociation rates. [Preview Abstract] |
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K1.00025: Valence photoionization of small alkaline earth atoms endohedrally confined in C$_{60}$: From the many-electron collectivity to single-electron interferences Mohammad Javani, Meghan McCreary, Aakash Patel, Mohamed Madjet, Himadri Chakraborty, Steve Manson Results of a theoretical study of the photoionization from outermost orbitals of Be, Mg and Ca atoms endohedrally confined in C$_{60}$ are presented. The fullerene ion-core of sixty C$^{4+}$ ions is smudged into a continuous jellium distribution while the delocalized cloud of carbon valence electrons, \textit{plus} the encaged atom, are treated in the time-dependent local density approximation (TDLDA) [1]. Systematic evolution of the mixing of outer atomic level with the C$_{60}$ band is detected along the sequence. This is found to influence the plasmon-driven enhancement at low energies and the geometry-revealing confinement oscillations from multi-path interferences at high energies in significantly different ways. The study paints the first comparative picture of the atomic valence photospectra for alkaline earth metallofullerenes in a dynamical many-electron framework [2].\\[4pt] [1] M.E. Madjet et al., \textit{Phys. Rev. }A \textbf{81}, 013202 (2010)\\[0pt] [2] M.H. Javani et al., \textit{to be published}. [Preview Abstract] |
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K1.00026: Cooper Pair Formation in Acenes Tim Hartman, Pavle Jurani\'c, Kelly Collins, Bethany Reilly, Narayana Appathurai, Scott B. Whitfield, Ralf Wehlitz We have measured the ratio of doubly to singly charged molecular parent ions of benzene, naphthalene, anthracene, and pyrrole over a wide range of photon energies. About 40 eV above the double-ionization threshold, the first three of the above molecules exhibit a hump of very similar shape and magnitude in the double-to-single photoionization ratio, which we attribute to the formation and emission of an electron Cooper pair from a free molecule. Our results suggest that the de Broglie wave of this highly correlated pair of electrons forms a closed loop in the system of overlapping $\pi$ bonds with a wavelength that matches the distance between neighboring carbon atoms. Pyrrole with its pentagonal structure does not allow the formation of a closed de Broglie wave and, thus, does not exhibit a hump in the ratio. Photoelectron measurements indicate the break-up of the emitted Cooper pair by two electron peaks sitting on top of the mainly U-shaped double-ionization continuum in support of our interpretation. [Preview Abstract] |
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K1.00027: Dissociative and non-dissociative photo double ionization of hydrocarbon molecules: C$_{2}$H$_{4}$ and C$_{2}$H$_{2}$ B. Gaire, P. Braun, I. Bocharova, F. Sturm, D. Haxton, A. Belkacem, Th. Weber, C.L. Cocke, A. Landers, R. Dorner Dissociative and non-dissociative ionization is observed when molecules interact with photons of energy near the double ionization threshold. Non-dissociative ionization will lead to a stable dication. The yield of the dication provides more information about the dicationic states involved. We explore the non-dissociative ionization of acetylene and ethylene molecules while employing the COLd Target Recoil Ion Momentum Spectroscopy (COLTRIMS) method. In contrast to the generation of acetylene dications, our measurements indicate that no stable ethylene dication can be produced via photo double ionization. We will discuss the role of non-adiabatic effects leading to the instant fragmentation of the ethylene dications into different breakup channels. [Preview Abstract] |
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K1.00028: Measuring 10 fs dynamics via resonant x-ray pump/x-ray probe spectroscopy Ryan Coffee, Mina Bionta, Nick Hartmann, James Cryan, James Glownia, Adi Natan, Doug French, Marco Siano We used two x-ray pulses to investigate the femtosecond scale molecular response to $K$-shell resonant excitation in O$_2$. Our results give three perspectives on this dynamic response: 1) sub-10 fs transient bleaching of resonant absorption, 2) a corresponding sub-10 fs evolution of the resonant Auger electron spectrum, and 3) a 10--15 fs evolution of electronic molecular symmetry. The x-ray pulses are tuned to the 531 eV $1s\rightarrow2p\pi^*$ resonance in O$_2$. Upon excitation by the first pulse, further absorption is suppressed until the dynamic molecular valence pulls a new valence state into resonance. The new resonance occurs only after about 5--10 fs and reveals opposite electronic symmetry to the $\pi$*. After 15 fs, this newly resonant state has lost molecular symmetry and undergoes atomic-like resonant absorption. We have thus used x-ray pump-probe spectroscopy to build a time-domain picture of the $\sim$10 fs molecular response to x-ray absorption. [Preview Abstract] |
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K1.00029: Time-Dependent Dirac Equation for Diatomics in SuperIntense Laser Fields -Numerical and Analytical results Andre D. Bandrauk, Francois Fillion-Gourdeau Numerical methods for solving the one-electron diatomic molecular Dirac equation in ultrashort(few cycles) superintense laser pulses are developped without Fermion-doubling. A split-operator method, originally developped for nonrelativistic time-dependent molecular problems is generalized using the method of characteristics [1]. Analytic results are also presented for a superintense static electric field to evaluate relativistic effects in diatomic CREI-Charge Resonance Enhanced Ionization [2].\\[4pt] [1] E Lorin, AD Bandrauk, Nonlinear Analysis, 12, 190(2011).\\[0pt] [2] T Zuo, AD Bandrauk, Phys Rev A 54,2511 (1995). [Preview Abstract] |
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K1.00030: Comparison of high-order harmonic generation of Ar atoms and H$_{2}$ molecules in intense 780~nm laser fields Dmitry A. Telnov, Shih-I Chu We analyze the high-order harmonic generation (HHG) of Ar atoms and H$_{2}$ molecules in 780~nm laser fields with the pulse duration about 30~fs and various peak intensities by means of the self-interaction-free time-dependent density functional theory (TDDFT). Since the ionization potentials of Ar and H$_{2}$ are close to each other, the cutoff position of the HHG spectra for the specific intensity is expected approximately at the same harmonic order, according to the three-step model. In general, our TDDFT calculations agree with this prediction; however, in the high-energy part of the HHG spectra, the harmonic signal from H$_{2}$ is considerably lower than that from Ar. On the other hand, the HHG spectrum of Ar has a prominent minimum at the photon energy 50~eV, especially for lower laser intensities. This minimum has the same nature as the well-known Cooper minimum in Ar observed in photoionization cross sections. [Preview Abstract] |
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K1.00031: Probing the spectral and temporal structures of macroscopic high-order harmonic generation of He in intense ultrashort laser pulses Peng-Cheng Li, I-Lin Liu, Cecil Laughlin, Shih-I Chu We present an accurate study of macroscopic high-order harmonic generation (HHG) from He atoms in intense ultrashort laser pulses. An accurate one-electron model potential is constructed for the description of the He atoms low-lying and Rydberg states. The macroscopic high-order harmonic spectra from He atoms are obtained by solving Maxwell's equation using macroscopic single-atom induced dipole moment. Macroscopic single-atom induced dipole moment can be obtained by solving accurately the time-dependent Schr\"odinger equation (TDSE) using the time-dependent generalized pseudospectral method (TDGPS). This method allows accurate and efficient propagation of the wave function with a modest number of spatial grid points, leading to the efficient treatment of the macroscopic propagation effects for HHG. Our results show fine structure and significant enhancement of the intensities of the lower harmonics due to the resonance transitions between bound states. We explain the temporal and spatial characteristics of HHG by means of the wavelet time-frequency analysis. These analyses help to understand the detailed HHG mechanisms from He atoms. [Preview Abstract] |
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K1.00032: Time-dependent theory of resonance fluorescence for ultrafast and ultraintense x rays Stefano M. Cavaletto, Zolt\'{a}n Harman, Christoph H. Keitel, Christian Buth The recent development of intense sources of coherent x-ray radiation such as the Linac Coherent Light Source (LCLS) in Menlo Park, California, USA, provides one with an unprecedented way to study nonlinear physics at short wavelengths. In this regard, resonance fluorescence, i.e. the spectrum of photons scattered off atoms and molecules driven by a near-resonant electric field, is expected to play a decisive role. We compute the time-dependent spectrum of resonance fluorescence of a two-level system excited by an ultrashort pulse. We allow for inner-shell hole decay widths and destruction of the system by further photoionization. This two-level description is employed to model neon cations strongly driven by LCLS light tuned to the $1s\,2p^{-1}\rightarrow 1s^{-1}\,2p$ transition at 848 eV: x rays induce Rabi oscillations which are so fast that they compete with Ne $1s$-hole decay. First, we predict resonance fluorescence spectra for chaotic pulses generated at present-day LCLS; second, we explore the exciting novel opportunities offered by Gaussian pulses which will become available in the foreseeable future with self-seeding techniques. In the latter case, we predict a clear signature of Rabi flopping in the spectrum of resonance fluorescence. [Preview Abstract] |
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K1.00033: Algorithm for Reconstruction of 3D Molecular Structure from Diffraction Patterns of Laser-Aligned Molecules Jie Yang, Christopher Hensley, Martin Centurion Ultrafast electron diffraction from laser-aligned gas molecules is a promising method for the determination of 3D molecular structures. Reconstruction algorithms for diffraction patterns of perfectly aligned molecules have been widely studied theoretically. However, under experimental conditions only partial alignment can be achieved and the existing algorithms do not perform well when the alignment is not perfect. We develop a method to reconstruct the 3D structure of molecules with cylindrical symmetry from electron diffraction patterns of partially-aligned molecules. The evolutionary algorithm assumes a known angular distribution, which can be calculated numerically using existing theory for laser-alignment and verified by comparison with the data. Selecting CF$_{3}$I as the cylindrically symmetric molecule, diffraction patterns from multiple alignment angles are used to reconstruct a single diffraction pattern corresponding to perfect alignment. The molecular structure can then be recovered from this pattern with no prior structural information required. Our results are in good agreement with previous models of CF$_{3}$I structure. [Preview Abstract] |
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K1.00034: Double-slit interference in H$_2^{\,+}$ subjected to ultrashort x-ray radiation Ethan Secor, Xiaoxu Guan, Klaus Bartschat, Barry I. Schneider Extending our earlier work~[1], we consider the double-slit interference effect [2,3] in the H$_2^{\,+}$ ion irradiated by intense short x-ray laser pulses with central photon energies from $200$-$500$ eV. The time-dependent Schr\"odinger equation in prolate spheroidal coordinates is solved to extract the angle-differential cross section of the photo\-electron. The spatical coordinates are discretized by means of a finite-element discrete-variable representation. We discuss the confinement effect [3] in the parallel geometry, in which the emission mode of the photoelectron along the laser polarization direction is dynamically forbidden. This confinement appears periodically, with the details depending on both the momentum of the electron and the internuclear separation. On the other hand, the effect disappears in the perpendicular geometry. We compare our results to those obtained from a simple plane-wave model based on time-independent perturbation theory.\\[4pt] [1]~X.~Guan, E.~Secor, K.~Bartschat, and B.~I.~Schneider, Phys.~Rev.~A~{\bf 84} (2011) 032420.\\[0pt] [2]~I.~G.~Kaplan and A.~P.~Markin, Sov. Phys. Dokl. {\bf 14} (1969) 36.\\[0pt] [3]~J.~Fern\'andez, F.~L.~Yip, T.~N.~Rescigno, C.~W.~McCurdy, and F.~Mart\'in, Phys. Rev. A {\bf 79} (2009) 043409. [Preview Abstract] |
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K1.00035: Dissociative single ionization of $CO^+$ molecular ions into $C^{2+} + O$ by intense laser pulses Nora G. Johnson, J. McKenna, A.M. Sayler, B. Gaire, M. Zohrabi, K.D. Carnes, I. Ben-Itzhak The charge asymmetric dissociative ionization (CADI) of a $CO^+$ molecular ion beam into $C^{2+} + O$ was studied by 7 and 40 fs intense ($10^{14}\phantom{i} W/cm^2$) laser pulses with both linear and circular polarization. Using a three-dimensional coincidence imaging technique, we detected both charged and neutral fragments. The measured kinetic energy release and angular distributions allow us to investigate the pathway leading to this CADI channel. Preliminary analysis suggests that the $CO^+$ is first excited in the leading edge of the laser pulse and later ionized to the $C^{2+} + O$ dissociative curve. We speculate that the initial stretching allows the molecule to be ionized beyond a curve crossing between the $C^{2+} + O$ and high lying $C^+ + O^+$ potentials, therefore enabling dissociation into the otherwise hard-to-reach CADI channel. This possible pathway and the dependence on intensity, polarization, and pulse duration will be discussed. [Preview Abstract] |
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K1.00036: Tracking Quantum Populations in Non-Sequential Double Ionization of Atoms Stan Haan, Christian Woolley, Katherine Shomsky We use one-dimensional quantum models to consider nonsequential double ionization of atoms in intense laser fields. We examine in particular the mixing of quantum states that is induced by the oscillating laser field. This mixing helps explain why classical models work so well -- even prior to recollision, the inner electron is in a mixture of ground and excited states. Recollision can change this mixture without needing a threshold energy for excitation from the ground to first excited state. [Preview Abstract] |
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K1.00037: Femtosecond transparency in the extreme ultraviolet Michal Tarana, Chris H. Greene Electromagnetically induced transparency-like behavior in the extreme ultraviolet (XUV) is studied theoretically, including the effect of intense 800\thinspace nm laser dressing of He 2s2p($^1P^o$) and 2p$^2(^2S^e$) autoionizing states. We present an \textit{ab initio} solution of the time-dependent Schr\"odinger equation in an \textsl{LS}-coupling configuration interaction basis set. The method enables a rigorous treatment of optical field ionization of these coupled autoionizing states into the $N = 2$ continuum in addition to $N = 1$. Our calculated transient absorption spectra show the formation of the Autler-Townes doublet in the presence of the dressing laser field. The presented results are in encouraging agreement with experiment [1]. \\[4pt] [1] Z.H. Loh, C.H. Greene, and S. R. Leone, Chem. Phys. 350, 7 (2008) [Preview Abstract] |
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K1.00038: The Phasemeter A.M. Sayler, T. Rathje, M. M\"{o}ller, D. Adolph, W. M\"{u}ller, D. Hoff, G.G. Paulus Intense few-cycle (4-8fs) laser pulses at 790 nm are now being used in a wide variety of applications, including the production of attosecond extreme-ultraviolet (XUV) pulses. Since these experiments are sensitive to the electric field of the laser light, the characterization and control of the waveform is critical for the understanding and manipulation of these interactions. We expand the usage of a stereographic laser-induced above-threshold ionization measurement of Xe (CEPM), i.e. the same technique optimized to provides precise, real-time, every-single-shot carrier-envelope phase and pulse length measurements of ultrashort laser pulses. This technique was restricted to sub-8fs laser pulses, however, by combining the CEPM with polarization gating; the acceptance region has been extended to a pulse length of 12fs. Together with real-time circuit, the CEPM also allows for improved the carrier-envelope phase stabilization of few-cycle laser pulse systems by 25\%. [Preview Abstract] |
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K1.00039: Carrier-envelope phase effects in few-cycle ionisation of atomic hydrogen David Kielpinski, W.C. Wallace, M.G. Pullen, O. Ghafur, D.E. Laban, A.J. Palmer, G.F. Hanne, A.N. Grum-Grzhimailo, K. Bartschat, I.A. Ivanov, A.S. Kheifets, X.-M. Tong, H.M. Quiney, I.V. Litvinyuk, R.T. Sang The control of strong-field photoionization with laser carrier-envelope phase (CEP) is the key enabling technique for attosecond science. Currently, quantitatively accurate \textit{ab initio} simulations of this process can only be carried out for atomic hydrogen. We have observed CEP effects in the above-threshold ionisation of atomic hydrogen for the first time. The modulation due to CEP is mapped over a wide range of laser intensity and electron energy. The data is compared with \textit{ab initio} simulations for the time dependent Schr\"{o}dinger equation carried out using three separate methodologies, as well as a semi-\textit{ab initio} simulation method. We find reasonable agreement between experiment and all simulations over the entire sampled parameter space. Our results point the way toward accurate calibration of absolute laser CEP by means of the uniquely calculable hydrogen system. [Preview Abstract] |
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K1.00040: The population trapping of Rydberg states in microwave ionization Alexandr Arakelyan, Stefan Salanski, Thomas Gallagher Previously, it was reported that when Rydberg atoms of Li are excited in the presence of a 17 or 36 GHz microwave field, the atom remains bound even if the excitation is above the limit [1]. We present another, more sensitive way to explore such microwave stabilization. Atoms of Li are excited to a high np Rydberg states during a 200 ns 38 GHz microwave pulse and surviving bound atoms are detected. As the last transition frequency is swept, the stable states spaced by an integer number of microwave photons are evident from at least -2000 GHz below the ionization limit (the energy of the zero field of n=45 state) up to 200 GHz over the limit with a microwave field of 85 V/cm. The interesting result is that these states exist even for binding energies in excess of 1100 GHz, which corresponds to a state of n=55, with a Kepler frequency of 38 GHz. Similar weakly bound final states are observed if bound Rydberg states are excited in zero field and then exposed to the microwave pulse. In this case the population transfer by a microwave pulse to the high lying states is about 10$\%$ of the total number of atoms initially excited to the Rydberg state, even when the microwave field is high enough that no other bound states survive.\\[4pt] [1] J.H. Gurian et al., Phys. Rev. A 82, 043415(2010). [Preview Abstract] |
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K1.00041: ATOMIC, MOLECULAR, AND CHARGED PARTICLE COLLISIONS II |
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K1.00042: An integro-differential transform to analytically reduce H$_{2}$ molecular integrals Jack Straton Molecular integrals that have a coordinate dependence akin to the bonding H$_{2}$ wave function are often carried out one-by-one, using hyper-spherical coordinates [1], Jacobi coordinates or bond-length coordinates [2], or confocal ellipsoidal coordinates [3]. An alternative strategy is to extend the general result developed by the author [4] for evaluating integrals of any number of products of multicenter ground-state or excited [5] atomic wave functions, Coulomb or Yukawa potentials, and Coulomb-waves [6] to include the H$_{2}$ molecular wave function. Modifications for semi-infinite integrals that terminate on a surface such as a Scanning Tunneling Microscope sample are also discussed. \\[4pt] [1] Y. Zhou, C. D. Lin and J. Shertzer, J. Phys. B: At. Mol. Opt. Phys. 26, 3937-3949 (1993).\\[0pt] [2] J. M. Hutson and P. Soldan, International Reviews in Physical Chemistry, 26(1) 1 - 28 (January 2007).\\[0pt] [3] J. P. Grivet, J. Chem. Educ., 79(1), 127 (2002).\\[0pt] [4] Jack C. Straton, \textit{Phys. Rev. A} \textbf{39}, 1676-84 (1989); Erratum \textit{Phys. Rev. A} \textbf{40}, 2819 (1989).\\[0pt] [5] Jack C. Straton, \textit{Phys. Rev. A}\textbf{ 41}, 71-7 (1990).\\[0pt] [6] Jack C. Straton, \textit{Phys. Rev. A} \textbf{42}, 307-10 (1990). [Preview Abstract] |
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K1.00043: Positron Reaction Microscope D.W. Mueller, C. Lee, C. Vermet, S. Armitage, D. Slaughter, L. Hargrave, A. Dorn, J. Brunton, S.J. Buckman, J.P. Sullivan We are developing a positron reaction microscope to measure kinematically complete ionization reactions of atoms and dissociative ionization of simple molecules by positron impact. The experiment is designed to use the slow positron beamline at the ARC Centre for Antimatter Matter Studies (CAMS) node at the Australian National University (ANU). This project is a collaboration among the University of North Texas, CAMS, and the Max Planck Insitute for Kern Phyzik in Heidelberg. Initial measurements and apparatus calibration will be performed using electrons. For positron measurements, the apparatus will be rolled into position on the slow positron beamline at the CAMS site at ANU. [Preview Abstract] |
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K1.00044: Heavy-Rydberg ion-pair formation in collisions of Rydberg atoms with attaching targets Changhao Wang, Michael Kelley, F. Barry Dunning Collisions between K($n$p) Rydberg atoms and electron attaching targets can lead to the creation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair orbiting at large internuclear separations. The lifetimes of such states and their correlation with binding energy and the channels available for decay, which can be controlled by varying $n$, the Rydberg atom velocity, and the target species, are being investigated. The ion-pair states are produced in a small collision cell and allowed to exit to form a beam that passes between a pair of electrodes where their number and binding energy distribution is determined by electric field induced dissociation. Ion-pair production is analyzed with the aid of a Monte Carlo collision code that models both initial Rydberg electron capture and the subsequent evolution of the product ion pair. Research supported by the Robert A Welch Foundation. [Preview Abstract] |
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K1.00045: Three-Body Recombination of Ultracold Atoms Treated Classically Steve Ragole, Chris Greene Three-body recombination is an important loss process in quantum gases. A six-dimensional classical simulation of the process has been formulated and implemented numerically, and Newtonian results for the generalized recombination cross-section have been calculated. Preliminary comparisons to quantum mechanical results will be discussed at the meeting, and animations of the recombination trajectories will be presented and interpreted. [Preview Abstract] |
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K1.00046: Avalanche Mechanism for Multiple Atom Loss near an Efimov Atom-Dimer Resonance Eric Braaten, Dane Smith Three-body recombination in ultracold trapped atoms produces an energetic atom and dimer that can escape from the trap. If the scattering cross sections are sufficiently large, rescattering of the escaping atoms and dimer can create an avalanche of lost atoms. As shown by Zaccanti et al., this mechanism can be enhanced by the existence of an Efimov trimer near the atom-dimer threshold. We use Monte Carlo methods to generate cascades initiated by recombination events. The energy dependence of the universal atom-dimer cross section associated with a large scattering length is fully taken into account. Every atom in the cascade either escapes or remains trapped, in which case its energy is eventually converted into heat. We calculate the average number of atoms lost and the heat produced by the avalanche mechanism as functions of the atom-atom scattering length. The existence of an Efimov trimer near the atom-dimer threshold can produce a relatively narrow peak in the atom loss rate. [Preview Abstract] |
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K1.00047: A diabatic hyperspherical method for three-body recombination rates: application to H $+$ H $+$ He $\rightarrow$ H$_2$ $+$ He Nicolais L. Guevara, W. Blake Laing, Brett D. Esry The formation of the hydrogen molecule through three-body recombination reactions was very important in the early universe. During the last decade, we have seen important progress in the calculation of three-body recombination rates. Most of them, however, have been focused on ultracold temperatures. Here, we present a method to study three-body recombination reactions that can handle temperatures of astrophysical interest and also many diatomic states. Our method introduces diabatic states in hyperspherical coordinates based on physical arguments to simplify the numerical calculations. In the present work, we have studied the reaction H + H + He $\rightarrow$ H$_2$ + He in order to test the utility and efficiency of our approach. Prospects for extending our method to other systems will be discussed. [Preview Abstract] |
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K1.00048: Electron-impact ionization of Al$^{2+}$ and Al Di Wu, S.D. Loch, C.P. Ballance, Sh.A. Abdel-Naby, M.S. Pindzola Electron-impact ionization cross sections are calculated for Al$^{2+}$ and Al. The non-perturbative R-Matrix with PseudoStates (RMPS) method was used to calculate the direct ionization of the 3s and 2p subshells and the indirect ionization of the 2p subshell for Al$^{2+}$ in a single, comprehensive calculation. This model agrees well with the experimental measurement of Thomason and Peart [1]. For Al, the RMPS and time-dependent close coupling methods are used to calculate cross sections for incident energies ranging from 5 to 30 eV. The non-perturbative close-coupling methods are found to be substantially lower than the perturbative distorted-wave cross sections due to electron correlation effects in both the direct ionization and indirect excitation-autoioniozation contributions. In addition, the close-coupling cross sections are found to be in good agreement with experiment [2]. \\[4pt] [1] J. W. Thomason and B. Peart J Phys B {\bf 31} L 201 (1998)\\[0pt] [2] R. S. Freund et al Phys. Rev. A {\bf 41} 3575 (1990) [Preview Abstract] |
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K1.00049: Interchannel coupling effects in multi-channel potential scattering Dmitri Sokolovski, Zineb Felfli, Alfred Z. Msezane There has been an increasing interest in resonance effects which arise when collision partners form a long-lived intermediate complex. An isolated resonance can be associated with a pole of the scattering matrix either in the complex energy or the complex angular momentum (CAM) plane. Observables of interest such as integral and differential cross sections are conveniently described by CAM (Regge) poles. Here a direct method for calculating Regge pole positions and residues, suitable for systems with a relatively small number of channels is proposed. The method is applied to a simple model designed to mimic electron-atom scattering at energies between the first and the second excitation thresholds. It is shown that interchannel coupling splits degenerate Regge trajectories into ones corresponding approximately to the two adiabatic potentials used. Nonadiabatic effects are found to be responsible for self-intersection of a Regge trajectory [1], not observed in single channel scattering. Envisioned is the possibility to probe Regge resonances and Feshbach resonances occurring in Bose-Einstein condensates. \\[4pt] [1] D. Sokolovski, Z. Felfli and A. Z. Msezane, Physics Letters A 376, 733 (2012) [Preview Abstract] |
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K1.00050: Eletron-helium laser-assisted free-free scattering with variable laser polarization B.A. deHarak, Benjamin Nosarzewski, Mahsa Siavashpouri, 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. In previous experiments\footnote{B. A. deHarak, L. Ladino, K. B. MacAdam and N. L. S. Martin, Phys. Rev. A {\bf 83}, (2011) 022706.} we examined the range of incident electron energies from 50~eV to 350~eV, and found the results to be in good agreement with the Kroll-Watson approximation (KWA).\footnote{N. M. Kroll and K. M. Watson, Phys. Rev. A 8, 804 (1973)} In these experiments the laser polarization was fixed relative to the scattering plane. Experiments are now being carried out where, at each electron energy, the direction of the polarization is varied within a plane perpendicular to the scattering plane. Of particular interest is the case where the polarization is perpendicular to the scattering plane for which the KWA predicts vanishing cross section. Other workers have found that the KWA tends to be inaccurate for those cases when it predicts small cross sections.\footnote{M. O. Musa, A. MacDonald, L. Tidswell, J. Holmes, and B. Wallbank, J. Phys. B, 43 (17):175201, 2010.} [Preview Abstract] |
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K1.00051: P-wave electron-hydrogen scattering Anand Bhatia A variational wave function incorporating short range correlations via Hylleraas type functions plus long-range polarization terms of the polarized orbital type but with smooth cut-off factors has been used to calculate P-wave phase shifts for electron-hydrogen scattering. This approach gives the direct r$^{-4}$ potential and a non-local optical potential which is negative definite. The resulting phase shifts have rigorous lower bounds and the convergence is much faster than those obtained without the modification of the target function. Final results will be presented at the conference. [Preview Abstract] |
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K1.00052: Progress Report on O($^{1}$D) production from oxygen-containing molecules William McConkey, Wladek Kedzierski, Jeff Hein O($^{1}$D) is an important species in the earth's atmosphere giving rise to the well known oxygen red lines at wavelengths of 630.0 and 636.4 nm from the upper atmosphere and strongly influencing stratospheric photochemistry. O($^{1}$D) is metastable and is difficult to detect selectively in the laboratory. We have developed techniques and instrumentation involving a solid Ne matrix at 10K that is sensitive to this species through the formation of excited excimers (NeO*) which immediately radiate. Using a pulsed electron beam and time-of-flight techniques we have measured relative cross sections as a function of impact electron energy for a number of targets including N$_{2}$O and CO$_{2}$. Threshold energy data are used to gain information about the parent molecular states. [Preview Abstract] |
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K1.00053: Electronic excitation of furan molecules by low energy electron impact Gabriela Serna, Leigh Hargreaves, Murtadha A. Khakoo, Maria Christina A. Lopes, Romarly da Costa, Marcio H.F. Bettega, Marco A.P. Lima Absolute differential and integral cross sections are presented for electron impact excitation of the $^{3}$B$_{2}$ and $^{3}$A$_{1}$ states of furan. The energy range of the present data set was 5-15eV. The measurements were normalized relative to the elastic cross section data of [1] and are compared to new calculations employing a multi-state Schwinger Multichannel approach with pseudopotentials [2]. The differential cross sections are peaked in the backwards direction, which is characteristic for optically forbidden transitions. Agreement between experiment and theory is good in some cases, although discrepancies remain, particularly above the ionization threshold. These differences are currently being investigated. The influence of polarization and multichannel coupling effects is also examined. \\[4pt] [1] M.A. Khakoo et al., Phys Rev A, \textbf{81}, 062716 (2010)\\[0pt] [2] M. H. F. Bettega, L. G. Ferreira, and M. A. P. Lima, Phys. Rev. A \textbf{47}, 1111 (1993) [Preview Abstract] |
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K1.00054: Momentum imaging of dynamical processes in dissociative electron attachment: resolving a mystery in CO2 Daniel Slaughter, Hidehito Adaniya, Thomas Rescigno, Daniel Haxton, Ann Orel, C. William McCurdy, Ali Belkacem We will report recent developments and experimental results of the dynamics of dissociative electron attachment (DEA) to CO2 by momentum imaging of the dissociating transient anion resonance. A 4-pi solid angle momentum spectrometer of the experimental apparatus, consisting of a pulsed electron beam, an electrostatic lens and a time-and position-sensitive detector, enables the measurement of the full 3D momentum distribution of dissociating negative ions. When combined with the spatial orientation of the incident electron, determined by ab initio theoretical methods, the ion momentum distribution yields a wealth of information relevant to the dynamical study of DEA. Recent experimental results for CO2 have confirmed the known three DEA resonances, leading to CO + O-, at 4.4, 8.2, 13.0 eV electron energies, where we have discovered unique momentum distributions specific to each resonance. Combining these experimental results with ab initio theoretical calculations, we have resolved a long standing misconception for the 8.2 eV and 4 eV resonances. [Preview Abstract] |
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K1.00055: Potential energy surfaces of metastable CO$_2^-$ for dissociative electron attachment Daniel Haxton, C.W. McCurdy, Tom Rescigno, Spiridoula Matsika I present potential energy surfaces of the metastable electronic states of the CO$_2^-$ anion relevant to dissociative electron attachment, which proceeds via two electronic states at approximately 4 and 8eV. DEA of CO$_2$ has been studied by many authors [including Dressler and Allan, Chem Phys 92, 449 (1985); Huels, Parenteau, Cloutier, and Sanche, J Chem Phys 103, 6775 (1995)], but the specific mechanisms of DEA to CO$_2$ have not been fully elucidated. The anion system is relevant in other contexts including catalytic conversion of CO. In a combined theoretical and experimental study of this system, we have established [J Phys B 44, 205203 (2011)] that the 8eV resonance is indeed a Feshbach resonance of $^2\Pi_g$ symmetry. The system of potential energy surfaces of this pair of states and the pair of states correlating to the 4eV $^2\Pi_u$ shape resonance that is responsible both for DEA and vibrational excitation at this energy, as well as that of the lowest energy anion state that begins as a virtual state at linear geometry and becomes the bound bent CO$_2^-$, explain the mechanisms of DEA and provide guidance to understand the current results of D. Slaughter, A. Belkacem et al which include angular and kinetic energy distributions of the fragments. [Preview Abstract] |
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K1.00056: Low-Energy Electron Scattering by Sugarcane Lignocellulosic Biomass Molecules Eliane Oliveira, Sergio Sanchez, Marcio Bettega, Marco Lima, Marcio Varella The use of second generation (SG) bioethanol instead of fossil fuels could be a good strategy to reduce greenhouse gas emissions. However, the efficient production of SG bioethanol has being a challenge to researchers around the world. The main barrier one must overcome is the pretreatment, a very important step in SG bioethanol aimed at breaking down the biomass and facilitates the extraction of sugars from the biomass. Plasma-based treatment, which can generate reactive species, could be an interesting possibility since involves low-cost atmospheric-pressure plasma. In order to offer theoretical support to this technique, the interaction of low-energy electrons from the plasma with biomass is investigated. This study was motived by several works developed by Sanche et al., in which they understood that DNA damage arises from dissociative electron attachment, a mechanism in which electrons are resonantly trapped by DNA subunits. We will present elastic cross sections for low-energy electron scattering by sugarcane biomass molecules, obtained with the Schwinger multichannel method. Our calculations indicate the formation of $\pi $* shape resonances in the lignin subunits, while a series of broad and overlapping $\sigma \ast $ resonances are found in cellulose and hemicellulose subunits. The presence of $\pi $* and $\sigma $* resonances could give rise to direct and indirect dissociation pathways in biomass. Then, theoretical resonance energies can be useful to guide the plasma-based pretreatment to break down specific linkages of interest in biomass. [Preview Abstract] |
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K1.00057: Positron scattering measurements from Krypton and Xenon James Sullivan, Joshua Machacek, Casten Makochekanwa, Adric Jones, Peter Caradonna, Daniel Slaughter, Stephen Buckman, Dennis Mueller As a part of a comprehensive program of low energy positron scattering, measurements have been made for a variety of scattering processes from the heavier rare gases, krypton and xenon. In the case of positron scattering, there have been large disagreements between different experiments, and experimental and theoretical determinations of scattering cross sections for these targets. A wide range of low energy positron scattering measurements is now possible, thanks to the development of the Surko trap and beam system, which provides a high energy resolution source of positrons [1-3]. The resulting positron beam is magnetised, and techniques developed for measuring cross sections in the magnetic fields mean that a wide range of scattering processes are now able to be investigated with high accuracy. This presentation will present measurements of total scattering, positronium formation and elastic differential scattering for both of these targets. The strongly forward peaked nature of the differential cross sections will be highlighted, especially as it relates to previous disagreements between different experimental measurements of the grand total cross section. In the case of positronium formation, the difference between present measurements and previous studies will also be discussed. [1] T. Murphy and C. M. Surko, Phys. Rev. A \textbf{46}, 5696 (1992) [2] S. J. Gilbert et al., Appl. Phys. Lett. \textbf{70}, 1944 (1997) [3] J. P. Sullivan et al. Phys. Rev. A \textbf{66}, 042708 (2002) [Preview Abstract] |
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K1.00058: Direct and indirect annihilation channels in positron-atom scattering Sergey Yakovlev, Vladimir Roudnev, Vitaly Gradusov, Michael Cavagnero We study positron-atom scattering on the base of Faddeev-Merkuriev equations in configuration space. Decomposition of the wave function into components corresponding to different asymptotic channels provides a way to separate the direct annihilation channel from the annihilation through positronium formation. The first, short time scale process corresponds to direct collisions between the positron and the atomic shell. The second process has a time scale of the positronium half-life. The result is illustrated with positron-Hydrogen scattering calculations at low energies. [Preview Abstract] |
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K1.00059: Modeling X-ray Emission due to Charge Exchange P.C. Stancil, J.L. Nolte, R.L. Porter, R.L. Shelton, Y. Wu, D.R. Schultz, Y. Hui, M.J. Rakovic, G.J. Ferland, H.P. Liebermann, R.J. Buenker Since the advent of Cravens' [1] proposal that the observed X-ray emission from comet Hyakutake was due to charge exchange (CX) of highly-charged solar wind ions with cometary neutrals, the CX-mechanism has been identified as a possible dominant contributor to the X-ray emission observed in the heliosphere, planetary exospheres, the geocorona, supernova remnants, starburst galaxies, and molecular cooling flows in galaxy clusters. To provide reliable CX-induced X-ray spectra models to simulate these and other astrophysical environments, we have undertaken a project to compute quantum-state-resolved CX cross sections of highly-charged ions colliding with H and He. Here we summarize current results for C$^{(5-6)+}$, N$^{6+}$, and O$^{(6-8)+}$ obtained with the molecular-orbital close-coupling (CC), atomic-orbital CC, and classical trajectory Monte Carlo methods. Utilizing the theoretical CX cross sections, cascade models are computed to generate X-ray spectra and compared to available measurements and observations. Comparison is also made to models assuming excitation by thermal electrons to identify diagnostics to distinguish CX-induced and electron-impact-induced X-ray emission.\\[4pt] [1] T. E. Cravens, {\it Geophys. Res. Lett.} {\bf 25}, 105 (1997). [Preview Abstract] |
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K1.00060: 3D imaging of molecular-ion dissociation following slow impact with atomic targets Ben Berry, Nora G. Johnson, Wania Wolff, A. Max Sayler, Dag Hathiramani, Jack W. Maseberg, Sam Fahrenholtz, K.D. Carnes, I. Ben-Itzhak Collisions between few keV molecular ions and atoms result primarily in collision-induced dissociation (CID) and dissociative capture (DC). The CID process can be a result of vibrational excitation; however, previous experimental efforts were unable to resolve the vibrational process from the competing electronic excitation, complicating comparison with theory. Employing coincidence 3D momentum imaging of the ion beam fragments and recoil ions, we are able to experimentally separate the vibrational (vCID) and electronic (eCID) processes, giving new insight into the vibrational mechanism. We investigate the influence of alignment and orientation of the molecule on eCID and vCID as well as other collision channels. In addition, we address the fate of the target atom following these collisions. A sample of results exploring CID and other processes occurring in such collisions will be presented. [Preview Abstract] |
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K1.00061: QUANTUM OPTICS, MATTER OPTICS, AND COHERENT CONTROL II |
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K1.00062: Enhancement of mechanical Q-factors by optical trapping J.D. Hood, K.-K. Ni, R. Norte, D.J. Wilson, S.P. Yu, A.M. Jayich, O. Painter, H.J. Kimble The quality factor (Q) of a mechanical resonator is an important figure of merit for observing quantum behavior. We demonstrate a technique to push the quality factor of a micro-mechanical resonator beyond conventional material and fabrication limits by using an optical lattice to trap a particular motional mode. A majority of the resonator's energy is stored in the lossless optical potential, thereby strongly diluting the effect of material dissipation. The pendulum-like mechanical resonator consists of a suspended 10 $\mu$m diameter, 140 nm thick Si0$_2$ disk attached to the substrate by a single thin tether. The disk is trapped at the intensity maximum of an optical lattice, and we observe a frequency increase of the center of mass from 6.2 KHz to 145 KHz with a 50 fold Q increase to a final value of $5.8\times10^{5}$. This technique shows a strong potential in bringing other micro-mechanical resonators, such as SiN membranes, into a low-loss regime where observation of quantum behavior in macroscopic devices at room temperature becomes possible. [Preview Abstract] |
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K1.00063: Impact of Decoherence on Internal State Cooling using Optical Frequency Combs Spencer Horton, Svetlana Malinovskaya We discuss femtosecond Raman type techniques to control molecular vibrations, which can be implemented for internal state cooling from Feshbach states with the use of optical frequency combs. We analyzed the use of an optical frequency comb, with and without modulation, as a viable substitute to the STIRAP process. In our theoretical model we take into account decoherence in the form of spontaneous emission and collisional dephasing in order to ascertain an accurate model of the population transfer in a three level system. We analyze the effects of odd and even chirps of the optical frequency comb in the form of sine and cosine functions on the population transfer. We compared the effects of these chirps to the results attained with a standard optical frequency comb to see if they increase the number of molecules that eventually end up in the final deeply bound state in the presence of decoherence. We also analyzed the inherent phase relation of the collisional dephasing between each of the states. This ability to control the rovibrational states of a molecule with an optical frequency comb enables us to create a deeply bound ultracold polar molecule from the Feshbach state. [Preview Abstract] |
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K1.00064: Coupling phonons and spins in diamond Steven Bennett, Shimon Kolkowitz, Quirin Unterreithmeier, Peter Rabl, Ania Bleszynski-Jayich, Jack Harris, Mikhail Lukin We present theoretical considerations for coupling quantized mechanical motion to the electronic spin of a nitrogen-vacancy (NV) defect center in diamond. In a recent experiment, a single NV spin was used to detect both driven and thermal motion of a magnetic force microscope cantilever at room temperature, reading out the spin state optically. This demonstration raises interesting theoretical questions, such as the feasibility of reaching the strong coupling regime and of measuring the quantum zero-point motion of the cantilever using the NV spin as a detector. We discuss these possibilities for the magnetically coupled system, as well as alternative spin-phonon coupling mechanisms in diamond with prospects for improved magnetometry and mechanical cavity QED. [Preview Abstract] |
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K1.00065: Coulomb barrier and exchange interaction in dynamical two-electron systems Maxwell Gregoire, Pavel Lougovski, Herman Batelaan Recent electron sources can produce pulses containing multiple electrons that are confined both laterally and longitudinally. Given that the highest reported degeneracy for continuous sources of free electrons is about 10$^{-4}$, it would be interesting to know the degeneracy for these pulsed sources. We previously studied one-dimensional two-electron degeneracy [1], and we now study three-dimensional two-electron degeneracy as a function of time. Our primary goal is to use this project as a necessary step to studying three-dimensional n-electron degeneracy. Our second goal is to develop a theory that predicts the outcome of Hasselbach's experiment demonstrating the Hanbury Brown-Twiss Effect [2] for free electrons.\\[4pt] [1] Lougovski P, and Batelaan H, Phys. Rev. A 84, 023417 (2011).\\[0pt] [2] Kiesel H, Renz A, and Hasselbach F, Nature. 418, 392-4 (2002). [Preview Abstract] |
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K1.00066: Theory of laser cooling of nuclear spins based on coherent population trapping Adi Pick, Michael Gullans, Yiwen Chu, Emre Togan, Susanne Yelin, Mikhail Lukin Nuclear spins, associated with $^{13}$C impurities in diamond, can be controlled via optical manipulation of localized atom-like impurities. Specifically, spectroscopic techniques involving coherent population trapping were recently used to control and monitor the nuclear state evolution. In this work, we present the physical mechanism which leads~to optical pumping of the nuclear spin ensemble into particular nuclear states. We propose an optimized scheme for achieving maximal control over the system. Specifically, cooling and control of the nuclear environment of the Nitrogen Vacancy Centers in diamond~leads to improved electronic coherence properties. In addition, it opens up the possibility of using the nuclear ensemble itself for quantum information applications. [Preview Abstract] |
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K1.00067: Oil droplet versus electron double slit diffraction Eric Jones, Adam Lif, Scot McGregor, Roger Bach, Herman Batelaan The double-slit experiments for photons and electrons are considered cornerstones of modern physics. Feynman's account of these experiments is one of the most popular. To get as close to Feynman's description of double-slit diffraction we did some experiments. This includes closing individual slits on demand, and taking a movie of the build-up of the diffraction pattern one particle at a time. In recent work done in Paris [1], macroscopic particle-wave duality with bouncing oil droplets was demonstrated for the first time ever. This may have implications for microscopic or quantum-mechanical particle-wave duality for electrons and photons. We will report on our attempts to reproduce the Paris results, and show new results of the individual droplet trajectories and how they compare to de Broglie-Bohm trajectories. \\[4pt] [1] Yves Couder and Emmanuel Fort, Phys. Rev. Lett. 97, 154101 (2006) [Preview Abstract] |
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K1.00068: Classical Forces in Aharanov-Bohm Effects Scot McGregor, Adam Caprez, Herman Batelaan, Ryan Hotovy Our recent experimental and theoretical work will be reported on Aharanov-Bohm type effects [1]. This includes the experimental demonstration that the Matteucci-Pozzi phase shift is a result of a classical force [2], in contradiction to earlier claims that it is a Type-II Aharonov-Bohm effect [3]. This result is part of a larger discussion that is centered around a classical paradox. Aharonov and Rohrlich point out that this paradox is ``{\ldots} crucial for clarifying the entirely \textit{quantum} interactions of `fluxons' and charges [4].'' Surprisingly, the Lorentz force acting on an infinite solenoid in the presence of an approaching charge is neglected [4]. Inclusion of the Lorentz force, along with the electromagnetic field momentum, leads to conservation of momentum. This motivates further investigation of the dual of the Aharanov- Bohm effect in which a neutral magnetic moment passes a charged wire. The question of sorting out which phase shifts are accompanied by classical force and which ones are not is still a topic of much debate and we report on our efforts to settle the argument. \\[4pt] [1] Batelaan H and Tonomura A 2009~\textit{Phys. Today}~\textbf{62}~38--43\\[0pt] [2] Shawn A Hilbert~\textit{et al}~2011~\textit{New J. Phys.}~\textbf{13}~093025\\[0pt] [3] Matteucci G and Pozzi G 1985~\textit{Phys. Rev. Lett.}~\textbf{54}~2469\\[0pt] [4] Aharonov Y and Rohrlich D 2005~\textit{Quantum Paradoxes: Quantum Theory for the Perplexed}~(Weinheim: Wiley) [Preview Abstract] |
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K1.00069: Experimental Validation of Interferometry Simulations on an Atom Chip Violeta Prieto, Jason Alexander, Christopher Rowlett, William Golding, Patricia Lee We report on recent experimental progress towards developing a compact atom interferometer on an atom chip using a double-well potential. The interferometer uses $^{87}$Rb atoms magnetically confined in an atomic waveguide produced by wires on the surface of a lithographically patterned chip. The double-well potential is created by dynamically changing the current configuration on our atom chip. We use combinations of different current configurations with various external bias fields that can offer the means to coherently split the atomic cloud through dynamically adjusting the currents and bias fields. We consider real-time transformations between different double-well configurations adiabatically and non-adiabatically, and study their effects on the initially trapped atoms. [Preview Abstract] |
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K1.00070: Atomic Test of the Equivalence Principle in a 10-meter Tower Susannah Dickerson, Jason Hogan, David Johnson, Alex Sugarbaker, Tim Kovachy, Sheng-wey Chiow, Mark Kasevich We aim to explore and expand the limits of atom interferometry in a 10-meter tower at Stanford University. Atom interferometry uses the coherent splitting and recombination of atoms to make precision measurements of environmental parameters such as gravity, acceleration, or magnetic field. The apparatus has been designed to test Einstein's Equivalence Principle to a precision of $10^{-15}$g by simultaneously launching ultracold atoms of different mass (specifically $^{85}$Rb and $^{87}$Rb) and accurately observing their free-fall motion in a vacuum chamber. Although we will perform the measurements with low-density clouds of cold atoms, we have demonstrated our ability to cool the atoms by forming Bose-Einstein condensates of $^{87}$Rb. Cold, dilute clouds can be launched with an optical lattice into the interferometer region. Splitting the atoms with Bragg pulses allows for the creation of a Mach-Zehnder interferometer for the Equivalence Principle measurement. [Preview Abstract] |
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K1.00071: Toward a sub-ppb measurement of $\alpha$ using atom interferometry with Bose-Einstein condensates Ben Plotkin-Swing, Alan Jamison, Nathan Kutz, Subhadeep Gupta We are preparing to perform an interferometric measurement of the recoil frequency of ytterbium atoms in a Bose-Einstein condensate (BEC). Such a measurement will yield a sub part-per-billion determination of the fine structure constant, $\alpha$, and allow for stringent tests of QED. We present the design of our symmetric three-path BEC contrast interferometer, which is favorable for a precision measurement due to its insensitivity to vibrations and ac Stark shifts, and because the recoil phase varies quadratically with additional recoils. We choose Yb BECs as our atom source for its insensitivity to magnetic fields and its coherence properties. We discuss various possible sources of systematic error to our experiment, and our planned route to achieve sub-ppb precision. Mean-field effects are the largest potential source of systematic error. We present theoretical work that shows our ability to model these effects and subtract them from our final result. We report on current experimental progress, including diffraction of a Yb BEC using standing wave optical pulses --- short pulses for momentum-state beam-splitting and long pulses as mirrors --- as well as progress towards additional acceleration pulses in order to boost the recoil phase and achieve the desired precision. [Preview Abstract] |
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K1.00072: Quantum random walks with multiphoton interference and high order correlation functions Bryan Gard, Robert Cross, Petr Anisimov, Hwang Lee, Jonathan Dowling We show a simulation of quantum random walks with multiple photons using a staggered array of 50/50 beam splitters with a bank of detectors at any desired level. We discuss the multiphoton interference effects that are inherent to this setup, and introduce one, two, and threefold coincidence detection schemes. The use of Feynman diagrams are used to intuitively explain the unique multiphoton interference effects of these quantum random walks. [Preview Abstract] |
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K1.00073: Narrowband Source of Correlated Photon Pairs via Four-Wave Mixing in Atomic Vapour Bharath Srivathsan, Gurpreet Kaur Gulati, Mei Yuen Brenda Chng, Gleb Maslennikov, Dzmitry Matsukevich, Christian Kurtsiefer Many quantum communication protocols require entangled states of distant qubits which can be implemented using photons. To efficiently transfer entanglement from photons to stationary qubits such as atoms, one requires entangled photons with a frequency bandwidth matching the absorption profile of the atoms. In our setup, a cold $Rb^{87}$ atomic ensemble is pumped by two laser beams (780nm and 776nm) resonant with the $5S_{1/2}\rightarrow 5P_{3/2} \rightarrow 5D_{3/2}$ transition. This generates time-correlated photon pairs (776nm and 795nm) by nondegenerate four-wave mixing via the decay path $5D_{3/2}\rightarrow 5P_{1/2} \rightarrow 5S_{1/2}$. Coupling the photon pairs into single mode fibres and using silicon APDs, we observe $g^(2)$ of about $2000$ and pairs to singles ratio of 11.2\% (2800 photon pairs per second) with an optical bandwidth $<$ $30/(2\pi)$ MHz. [Preview Abstract] |
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K1.00074: Heterodyne-based optical probe with sub-kHz resolution for coherent atomic media Russell McLean, Alexander Akulshin We have demonstrated a coherent heterodyne technique for probing atomic media containing laser-induced coherence. Optical heterodyning with mutually coherent laser fields allows the detection of new spectral components generated by phase modulation and four wave mixing. The technique has sub-kHz resolution, well below the laser linewidth limit. We use two applied radiation fields tuned to particular transitions within the Rb D lines and separated by a small frequency offset, typically 100 kHz or less, to generate an enhanced atomic Kerr nonlinearity in a Rb vapour through the processes of coherent population trapping and coherent population oscillations. In the heterodyne technique the transmitted fields, including the new fields resulting from these processes, are mixed with a reference field tuned beyond the region of enhanced nonlinear susceptibility, to generate beat signals observable on an RF spectrum analyzer. With a suitable choice of polarizations for the two applied fields the technique has allowed us to distinguish the processes responsible for generating the enhanced nonlinearity, and represents a novel method of probing coherent atomic media that is complementary to the more commonly used drive-probe and Hanle-type methods. [Preview Abstract] |
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K1.00075: Power dependence of multi-photon processes in the $5S_{1/2}-5P_{3/2}-5D_{5/2}$ transition of $^{87}$Rb atoms Han Seb Moon, Heung-Ryoul Noh We have experimentally demonstrated the multi-photon effects of the ladder-type electromagnetically-induced transparency (EIT) according to the intensities of the probe and coupling lasers in the $5S_{1/2}-5P_{3/2}-5D_{5/2}$ transition of $^{87}$Rb atoms. When the intensity of the probe laser was comparable to one of the coupling laser, the transmittance spectra of the $5S_{1/2}(F=2)-5P_{3/2}(F'=3)-5D_{5/2}(F''=4)$ cycling transition were observed a variety of variation due to EIT and double-resonance optical pumping (DROP) according to the intensities of the probe and coupling lasers. The spectral features of the transmittance spectra were interpreted as the multi-photon processes composed of the one-photon resonance, the two-photon resonance, and the mixed term using the diagrammatic analysis of multi-photon processes. The observed transmittance spectra were a good agreement with the numerically calculated results by the full density matrix equations. [Preview Abstract] |
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K1.00076: Spectrum and photon statistics of an optomechanical cavity QED system Andrew Jacobs, James Clemens Work to date in cavity optomechanics has primarily focused on the coupling between the cavity field and the mechanical oscillator. We investigate a weakly driven, damped optomechanical cavity containing a two-level atom with an oscillating end mirror or an intracavity dielectric membrane. We carry out numerical simulations of the system using the framework of quantum trajectories implemented with the Quantum Toolbox in Python (QuTiP). We calculate the cavity probe spectrum and second-order field-field and atom-field correlations, finding they are modified by the coupling between the cavity field and the mechanical oscillator. [Preview Abstract] |
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K1.00077: Coherent optical excitations in superconducting qubit chain Hou Ian, Yu-xi Liu In the recent years, the theories of quantum optics have been borrowed to study the flows of electron pairs and their interactions with the circuit photon in the superconducting qubit circuits. These studies bring about new theories of quantum optics, such as the tunable electromagnetically induced transparency effect, peculiar to the Cooper pairs in circuits. In this talk, we focus on a special type of superconducting qubit circuits: superconducting qubit chain (SQC), which comprises dozens of qubits linearly placed along a stripline resonator. Since the dimensions of the qubits and the stripline have made their interactions inhomogeneous, the SQC cannot be diagonalized using the usual Dicke model. We present a new theoretical method, the deformation-projection method, for the exact diagonalization of the collective excitations of the qubits. This method allows us to predict that these excitations emulate the behaviors of Wannier and Frenckel excitons in the solid-state systems. The spontaneous emissions from the individual qubits in SQC are relayed to their neighbors, eventually arriving at a coherent emission, known as superradiance. We present a quantum relay model, which is crucial to quantum information processing, based on this finding. [Preview Abstract] |
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K1.00078: QUANTUM INFORMATION II |
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K1.00079: Fidelity analysis of a Rydberg blockade CNOT gate with simulated quantum process tomography X.L. Zhang, A.T. Gill, L. Isenhower, T.G. Walker, M. Saffman We present a detailed error analysis of a Rydberg blockade mediated controlled-NOT quantum gate between two neutral atoms. Numerical solutions of a master equation for the gate dynamics, including all known sources of technical error, are shown to be in good agreement with experiments. We also present numerical simulations of quantum process tomography to find the intrinsic fidelity, neglecting technical errors, of a Rydberg blockade controlled phase gate. The gate fidelity is characterized using trace overlap and trace distance measures. We show that the trace distance is linearly sensitive to errors arising from the finite Rydberg blockade shift and introduce a modified pulse sequence which corrects the linear errors. Error floors of $O(10^{-3})$ are found for $^{87}$Rb and Cs atoms. [Preview Abstract] |
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K1.00080: Towards experimental realization of a scalable ion chain quantum processor in microfabricated surface trap So-Young Baek, Emily Mount, Daniel Gaultney, Rachel Noek, Stephen Crain, Andre van Rynbach, Peter Maunz, Jungsang Kim Realization of a practical trapped ion quantum information processor is a major technological challenge that requires development of large-scale integration approaches. The integration technology must include scalable solution for both the qubit datapath and classical controllers necessary to manipulate them. Our approach utilizes linear ion chains in microfabricated surface traps as a platform to store Yb ion qubits and operate quantum logic gates on them. The control signals for qubit manipulation include the abilities to direct precisely tailored laser beams to individual ions, re-arranging the ions in the chains, and parallel detection of multiple qubits. We use a frequency comb generated by an off-resonant picosecond pulsed laser with stabilized repetition rate to drive Raman transitions, realizing single qubit and multiple qubit gates in an inherently scalable way. The laser beams will be delivered to individual ions using a microelectromechanical systems-based beam steering system that can easily be extended to multiple beams, and the parallel state detection will be performed using multi-element photomultiplier tube array. We will describe the experimental progress in implementing basic quantum information processing protocols in this system. [Preview Abstract] |
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K1.00081: Multi-second quantum memory based upon a single nuclear spin in a room temperature solid Peter Maurer, Georg Kucsko, Christian Latta, Liang Jiang, Norman Yao, Steven Bennett, Fernando Pastawski, David Hunger, Nick Chisholm, Mark Markham, Daniel Twitchen, Ignacio Cirac, Mikhail Lukin Room temperature solid-state quantum bit with second-long memory Realization of stable quantum bits (qubits) that can be prepared and measured with high fidelity and that are capable of storing quantum information for long times exceeding seconds is an outstanding challenge in quantum science and engineering. Here we report on the realization of such a stable quantum bit using an individual 13C nuclear spin within an isotopically purified diamond crystal at room temperature. Using an electronic spin associated with a nearby Nitrogen Vacancy color center, we demonstrate high fidelity initialization and readout of a single 13C qubit. Quantum memory lifetime exceeding one second is obtained by using controlled dissipative optical decoupling from the electronic degree of freedom. Techniques to further extend the quantum memory lifetime as well as the potential applications are also discussed. [Preview Abstract] |
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K1.00082: Enhanced solid-state multi-spin metrology using dynamical decoupling Linh Pham, Nir Bar-Gill, Chinmay Belthangady, David Le Sage, Paola Cappellaro, Mikhail Lukin, Amir Yacoby, Ronald Walsworth We use multi-pulse dynamical decoupling to increase the coherence lifetime (T2) of large numbers of nitrogen-vacancy (NV) electronic spins in room temperature diamond, thus enabling scalable applications of multi-spin quantum information processing and metrology. We realize an order-of-magnitude extension of the NV multi-spin T2 for diamond samples with widely differing spin environments. For samples with nitrogen impurity concentration $\ga$ 1 ppm, we find T2 $>$ 2 ms, comparable to the longest coherence time reported for single NV centers, and demonstrate a ten-fold enhancement in NV multi-spin sensing of AC magnetic fields. [Preview Abstract] |
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K1.00083: Classical Communication with Stimulated Emission over Zero-Capacity Optical Quantum Channels Laszlo Gyongyosi, Sandor Imre The superactivation of zero-capacity optical quantum channels makes it possible to use two zero-capacity optical quantum channels with a positive joint capacity for their output. The phenomenon is rooted in the extreme violation of additivity of the channel capacities of quantum channels. Recently, the most important discovery in quantum information theory was the possibility of transmitting quantum information over zero-capacity quantum channels. Before our work, the superactivation of the classical capacity of noisy optical quantum channels was an open question and seemed to be completely impossible. We show that using photon-based encoder and decoder setting, classical information can also be transmitted over the combination of zero-capacity optical quantum channels. The proposed scheme requires only the most natural process that occurs during stimulated emission. [Preview Abstract] |
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K1.00084: Long Distance Quantum Communication Using Cascade Emission in Atomic Ensembles Hsiang-Hua Jen The ladder configuration of atomic levels provides a source for telecom photons (signal) from the upper atomic transition. For rubidium and cesium atoms, the signal field has the range around 1.3-1.5 $\mu$m that can be coupled to an optical fiber and transmitted to a remote location. Cascade emission may result in pairs of photons, the signal entangled with the subsequently emitted infrared photon (idler) from the lower atomic transition. This correlated two- photon source is potentially useful in the DLCZ protocol for the quantum repeater. We investigate the role of time- frequency entanglement in the protocol, and find that it deteriorates the performance but the harmful effect can be diminished by using shorter pump pulses to generate the cascade emission. [Preview Abstract] |
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K1.00085: Trapped-ion Quantum Information Processing using Scalable Techniques Ryan Bowler, John Gaebler, Yiheng Lin, Ting Rei Tan, David Hanneke, John Jost, Jonathan Home, Adam Meier, Emanuel Knill, Dietrich Leibfried, David Wineland We report progress towards combining all the building blocks required for scalable quantum information processing using trapped atomic ions. Included elements are qubits with long coherence times, a laser-induced universal gate, motional state initialization using a second ion species, and information transport. We currently explore techniques to efficiently measure gate fidelity in a scalable way involving multiple qubits and randomized benchmarking. For this, we perform sets of quantum information sequences involving as many as 16 two-qubit entanglement gates and 50 single-qubit gates. We have also developed an arbitrary waveform generator with an update rate far above the ions' motional frequencies which is capable of rapidly bringing together and separating the qubit ions each time a two-qubit gate is performed. [Preview Abstract] |
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K1.00086: Progress towards a polarization spectroscopy experiment for quantum control of collective spin Pascal G. Mickelson, Enrique Montano, Daniel Hemmer, Poul S. Jessen We report preliminary results from an experiment that will implement quantum control of the collective spin of an atomic ensemble. In our setup, a weak probe laser interacts with a cold, trapped atomic sample of cesium atoms with high optical depth, leading to Faraday rotation of the probe light proportional to the atomic magnetization. If the atom-light coupling is strong enough, polarimetry of the probe light will provide a measurement of the magnetization with resolution better than the spin projection noise, at which point measurement back-action will become significant enough to be used for quantum control of the spin. Thus far, we have loaded cesium atoms into a $\sim$50 $\mu$K deep optical dipole trap, and we observe Faraday rotation of the probe light as it passes through this cloud of atoms. Work is ongoing to increase the optical depth of the atom sample and to optimize the atom-light coupling by mode-matching the probe beam to the atom sample. [Preview Abstract] |
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K1.00087: Estimation of a quantum interaction parameter using weak quantum measurement: theory and experiment Michael Goggin, Holger Hofmann, Marcelo Almeida, Marco Barbieri We investigate the metrological limits of the measurement of an interaction parameter based on a weak measurement and post-selection. A strict connection between weak values and the Fisher information of the measurement scheme is established. The resultant theory is applied to an experiment on the polarization of single photons. The experimental results support the theory and provide insight into the statistics of weak measurements. [Preview Abstract] |
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K1.00088: COLD ATOMS, MOLECULES, AND PLASMAS II |
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K1.00089: Experiments on the Verification of the 1-D Tan Relations for Bosons in an Atom Chip Waveguide Jason Alexander, Violeta Prieto, Christopher Rowlett, Patricia Lee, William Golding Recently it has been shown that a single quantity called the ``contact'' characterizes the behavior of interacting fermions at short distances. A set of universal relations was developed connecting the contact to the long range, thermodynamic properties of a gas of fermions. Some of these relations have been verified experimentally for fermions and bosons in three dimensions. As a result there has been a great deal of theoretical interest in this area and similar relations have been developed for bosons in 1-D. In this work, we continue to report results on the experimental verification of some of these 1-D relations for a system of bosons ($^{87}$Rb) confined to the (quasi) 1-D potential of an atom chip magnetic waveguide. We measure the contact via the momentum distribution for various inter-particle interaction strengths. We discuss how the contact can serve as a marker for the phase transitions between the thermal gas, the Bose-Einstein condensate, and the Tonks-Girardeau gas. Previously, we reported very preliminary results for a 1-D thermal gas. Here we report measurements of the contact for a 1-D condensate and discuss progress towards observing the transition to the Tonks-Girardeau regime for atoms in our atom chip waveguide. [Preview Abstract] |
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K1.00090: Expansion dynamics of a non-spherical ultracold plasma in a supersonic molecular beam Markus Schulz-Weiling, Ed Grant Molecular beam plasma dynamics are subject to a superposition of the residual molecular beam expansion of the laser illuminated excitation volume with ambipolar expansion owing to charged particle many-body interactions. We combine beam calculations with a consideration of the excitation processes that lead to plasma formation to determine the initial phase space distribution function of our plasma particles. Subsequent application of kinetic theory yields a model for the evolution of our system. By solving Vlasov's equation for our initial conditions, we obtain a first-order approximation for ambipolar expansion in the geometry of our system. [Preview Abstract] |
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K1.00091: Molecule Formation Experiments with Ultracold Gases of $^{23}$Na and $^6$Li Tout T. Wang, Myoung-Sun Heo, Timur M. Rvachov, Wolfgang Ketterle, David E. Pritchard We will describe progress towards making Feshbach molecules from an ultracold mixture of $^{23}$Na and $^6$Li. Molecule formation attempts were done around a closed-channel dominated Feshbach resonance at 796G, for which significant coupling between open and closed channel states occurs in a region less than 50mG wide. Our experimental configuration includes one part per 10$^5$ magnetic field stability, field ramps shaped to minimize time spent near resonance while maintaining adiabaticity, and an improved optical trapping geometry that gives faster separation of formed molecules from remaining atoms in a magnetic field gradient. We will also discuss the possibility of molecule formation in an optical lattice as well as features of the fermionic $^{23}$Na$^6$Li molecule in its ro-vibrational ground state. [Preview Abstract] |
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K1.00092: Characterization of an imaging system for cold Rydberg atoms Jader Cabral, Jorge Kondo, Luis Goncalves, Luis Marcassa In this work, we have built an imaging system for cold Rydberg atoms. The system consists of three grids, a tube of flight and a MCP (micro channel plates) detector with a phosphor screen. In one of the grid, we can apply a HV pulse to ionize the Rydberg atoms. DC voltages are applied on the other grids, which work as electrostatic lenses. By varying such voltages, we are able to get a better resolution in our MCP detector. The ions are detected by the MCP, with image them on the phosphor screen. We have obtained ion images of cold Rydberg atoms from a magneto optical trap as well as CO$_{2}$ dipole trap. The experimental images were compared with theoretical images obtained from a simulation, and a good agreement was observed. [Preview Abstract] |
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K1.00093: Towards production of ultracold molecular ions in a hybrid trap system Scott Sullivan, Wade Rellergert, Kuang Chen, Steven Schowalter, Svetlana Kotochigova, Eric Hudson We describe a new method for the production of ultracold molecular ions. This method utilizes sympathetic cooling due to the strong collisions between appropriately chosen molecular ions and laser-cooled neutral atoms to realize ultracold, internal ground-state molecular ions. In contrast to other experiments producing cold molecular ions, our proposed method efficiently cools both the internal and external molecular ion degrees of freedom. The availability of truly ultracold molecular ions will impact fields as diverse as quantum chemistry, precision measurement, and quantum information/computation. We present preliminary results towards demonstration of rovibrational relaxation in BaCl$^{+}$. [Preview Abstract] |
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K1.00094: Optical pulse-shaping for internal cooling of molecules Chien-Yu Lien, Chris Seck, Scott Williams, Brian Odom We propose a scheme to use pulse-shaped femtosecond lasers to optically cool the internal degrees of freedom of molecular ions. Since this approach relies on cooling rotational and vibrational quanta by exciting an electronic transition, it is most straightforward for molecular ions with diagonal Frank-Condon-Factors. Compared with schemes that cool rotations by exciting vibrations, this approach achieves internal cooling on the orders-of-magnitude faster electronic decay timescale and is potentially applicable to apolar molecules. For AlH$^{+}$, a candidate species, a rate-equation simulation shows that rovibrational equilibrium should be achievable in 8 $\mu$s. Progress towards the experimental realization of this scheme for rovibrational optical cooling AlH$^{+}$, including the molecular ion production technique, details of the optical pulse shaping, and the state readout scheme will be discussed. [Preview Abstract] |
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K1.00095: Achieving higher Gamma plasmas using higher ionization states Nathan Rock, Abigail Wilkins, Mary Lyon, Scott Bergeson A recent simulation predicted that higher values of the strong coupling parameter in ultracold neutral plasmas can be realized if the plasma ions are excited to higher ionization states. The maximum value of $\Gamma$ depends on the time at which the second ionization pulse arrives. We describe an experiment in laser-cooled calcium. Neutral atoms in a MOT are ionized using laser pulses at 423 and 390 nm. These ions are ionized again to Ca$^{2+}$ using laser pulses at 397, 210, and 434 nm. In this presentation we will describe the current status of the experiment. [Preview Abstract] |
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K1.00096: Few-body interactions in ultracold gases Jianing Han Recent experiments show that few-body interactions exist in ultracold gases. In this presentation, one-body, two-body, three-body, and four-body interactions will be illustrated. The results reported here provide useful information for gas to condensed phase transitions, and may be used for quantum information, high precision spectroscopy, as well as few-body entanglements. [Preview Abstract] |
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K1.00097: Collective Modes of Spin-Orbit Coupled Condensate Zhu Chen, Hui Zhai Collective modes of Spin-orbit coupled Bose-Einstein condensate in harmonic potential are studied systematically. The NIST type spin-orbit coupling is considered mainly due to its experimental realization. The dipole oscillation frequency turns out to be related to the oscillation magnitude, which is the reflection of the the violation of kohn's theorem. Analytical results are obtained in small amplitude limit, which are consistent with the effective mass theory. Breath modes and surface modes are also obtained, which are shown to be coupled with the center of mass motion. Mode resonance among them is observed. Furthermore, a special case is considered when center of mass motion in real space induces tunneling in momentum space. A simplified two-mode model is proposed to explain qualitatively such oscillation plus tunneling process. At last, the most general form of spin-orbit coupling is studied, and results in small amplitude limit are also obtained. [Preview Abstract] |
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K1.00098: From Anderson to Anomalous Localization in Cold Atomic Gases with Effective Spin-Orbit Coupling Johannes Otterbach, Matthew Edmonds, Mikhail Titov, Patrick \"Ohberg, Razmik Unanyan, Michael Fleischhauer The advanced techniques in coherently controlling and manipulating cold atomic gases allow for the formation of, e.g., artificial magnetic fields or the creation of effective Spin-Orbit coupling for neutral atoms. Confining such spin-orbit coupled particles to one dimension gives rise to an effective relativistic Dirac-like dynamics in the limit of small particle momenta. The addition of disorder potentials drastically changes the properties of these systems giving rise to phenomena as, e.g., exponential Anderson localization. Here we study the dynamics of ultracold atoms with an effective Spin-Orbit coupling moving in a one-dimensional random potential. We show that tuning the ratio between spin-orbit coupling and disorder strength leads to a crossover from exponential Anderson-like localization of massive particles to an anomalous power-law behavior. Its origin can be traced back to the emergence of a Dyson-like singularity in the density of states around the zero-energy (mid-gap) state, reminiscent of the so-called Random Mass Dirac model. [Preview Abstract] |
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K1.00099: Chaotic dynamics of dipolar condensates in optical traps Roxanne Moran, Boaz Ilan, Kevin Mitchell The potential energy of two-dimensional optical traps typically induces chaotic dynamics in the resulting classical trajectories. This has a profound impact on the transport and escape properties of ultracold atoms in such traps. Prior theory showed that attractive atomic contact interactions would enhance the relative importance of classical fractal structures in the quantum chaotic scattering, by reducing quantum dispersion. With recent experimental advances in creating degenerate dipolar gases, we seek to understand the relevance of long-range dipole-dipole interactions on the chaotic scattering and transport rates of gases in optical potentials. Given the theoretical predictions of two-dimensional solitons in such gases, we expect a correspondingly large enhancement in the role of classical fractal structures. [Preview Abstract] |
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K1.00100: Nonlinear dynamics and solitonic structures of two-component BECs Chris Hamner, JiaJia Chang, Peter Engels We present ongoing experimental studies of the rich nonlinear dynamics of two-component $^{87}$Rb BECs. These dynamics range from counterflow induced modulational instabilities to the formation of spin domains and novel solitonic structures, including soliton clusters. We report on the current status of the experiment. [Preview Abstract] |
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K1.00101: Experiments with Quantum Degenerate Atomic Strontium Mi Yan, Brian DeSalvo, Ying Huang, Ramachand Balasubramanian, Han Pu, Thomas Killian We will describe experiments with quantum degenerate gases of atomic strontium. We are able to produce Bose-Einstein condensates of $^{84}$Sr and quantum degenerate mixtures of $^{87}$Sr (fermion) and $^{88}$Sr (boson). With $^{88}$Sr we have demonstrated control over condensate dynamics with an optical Feshbach resonance and have developed tools to model the dynamics after a rapid change in scattering length. We will describe photoassociative spectroscopy near the $^{1}$S$_{0}-^{3}$P$_{1}$ atomic asymptote for various isotopes and the calculation of parameters for optical Feshbach resonances. We will also discuss our recent progress loading condensates into optical lattices. [Preview Abstract] |
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K1.00102: Thermodynamics of the two-component Fermi gas with unequal masses at unitarity K.M. Daily, D. Blume We consider mass-imbalanced two-component Fermi gases for which the unequal-mass atoms interact via a zero-range model potential with a diverging $s$-wave scattering length $a_s$, i.e., with $1/a_s=0$. The high temperature thermodynamics of the harmonically trapped and homogeneous systems are examined using a virial expansion approach up to third order in the fugacity. We find that the universal part of the third-order virial coefficient associated with two light atoms and one heavy atom is negative, while that associated with two heavy and one light atom changes sign from negative to positive as the mass ratio $\kappa$ increases, and diverges when Efimov physics sets in at $\kappa=13.61$. By examining the Helmholtz free energy, we find that the equilibrium polarization of the trapped and homogeneous systems is 0 for $\kappa=1$, but finite for $\kappa \ne 1$ (with a majority of heavy particles). Compared to the equilibrium polarization of the non-interacting system, the equilibrium polarization at unitarity is increased for the trapped system and decreased for the homogeneous system. We find that unequal-mass Fermi gases are stable for all polarizations. [Preview Abstract] |
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K1.00103: Two-dimensional Fermi gases Enrico Vogt, Michael Feld, Bernd Fr\"{o}hlich, Daniel Pertot, Marko Koschorreck, Michael K\"{o}hl We report on our latest investigations on two-dimensional Fermi gases. We present the studies on collective excitations of a harmonically trapped two-dimensional Fermi gas from the collisionless to the hydrodynamic regime in order to investigate scale invariance and viscosity. We additionally investigate balanced and imbalanced Fermi mixtures in optical lattices using momentum-resolved photoemission spectroscopy. Those measurements include the observation of a many-body pairing gap above the superfluid transition temperature in a harmonically trapped, two-dimensional atomic Fermi gas in the regime of strong coupling. Furthermore we report the creation and experimental investigation of both attractive and repulsive Fermi polaron quasiparticles in two dimensions, which result when a small number of spin-down $^{40}$K atoms are immersed in a two-dimensional Fermi sea of spin-up $^{40}$K atoms. The single-particle spectral function $A(k,E)$ of the Fermi polarons, which directly reveals the quasi-particle properties like the energy and effective mass, is measured giving access to the full (momentum-resolved) quasiparticle dispersion. [Preview Abstract] |
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K1.00104: A new strongly interacting Bose-Fermi mixture of $^{23}$Na and $^{40}$K Cheng-Hsun Wu, Ibon Santiago, Jee Woo Park, Peyman Ahmadi, Sebastian Will, Martin Zwierlein We have created a quantum degenerate Bose-Fermi mixture of $^{23}$Na and $^{40}$K with widely tunable interactions via broad interspecies Feshbach resonances. Over thirty Feshbach resonances between $^{23}$Na and $^{40}$K were identified, including p-wave multiplet resonances. Observed broad Feshbach resonances opens up a path to study the fate of an impurity interacting with its environment, a fundamental problem in condensed matter physics. We study the interaction of an impurity immersed in a Bose-Einstein condensate of $^{23}$Na. We perform radio-frequency spectroscopy on the impurity atom and the bath, which is expected to probe the spectral features characteristic for polaronic dressing: A delta-like peak in addition to a broad pedestal coming from the interactions between the impurity and the phonons in the condensate. Our system, with its widely tunable interactions, promises to be an ideal system to study the evolution from Bose polarons to Fermi polarons as the imbalance between $^{23}$Na and $^{40}$K is varied. [Preview Abstract] |
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K1.00105: Ultracold Molecules in Lattices for Metrology and Precision Measurements Gael Reinaudi, Chris Osborn, Mickey McDonald, Dili Wang, Tanya Zelevinsky Ultracold diatomic molecules offer exciting possibilities for studies of novel states of matter, quantum information, and metrology. Two-electron-atom based molecules are particularly promising for precision measurements, such as molecular time metrology and variations of the proton-electron mass ratio. We present an experimental setup that allows for the photoassociation, in an optical lattice, of strontium atoms into molecules using the narrow singlet-triplet transitions. We feature newly observed two-photon photoassociation to deeply bound molecular levels, as well as the study of the lifetime of such molecules in lattices, which is a determining factor concerning the practical use of this system. Other characteristics of our setup are presented, such as a computer controlled permanent-magnet Zeeman slower optimized with a genetic algorithm. [Preview Abstract] |
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K1.00106: Stable blue detuned trap arrays for multi-qubit quantum gate experiments Michal Piotrowicz, Kara Maller, Marty Lichtman, Siyuan Zhang, Gang Li, Larry Isenhower, Mark Saffman We have implemented a new approach to trapping single atom qubits using an array of blue detuned Gaussian laser beams which overlap weakly. This creates a two-dimensional array of 3D trap sites that are spatially stable, and are insensitive to phase drifts due to wavelength scale motion of the optical elements used for beam projection. A combination of diffractive and refractive optics is used to generate the beam array with high efficiency. We report on progress towards trapping and quantum state control of single Cs atoms in the array. [Preview Abstract] |
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K1.00107: Ultracold Fermions in an Optical Lattice with Tunable Geometry Gregor Jotzu, Leticia Tarruell, Daniel Greif, Thomas Uehlinger, Tilman Esslinger Ultracold Fermi gases in optical lattices have emerged as a versatile tool to simulate condensed matter phenomena. We present an optical lattice whose potential can be dynamically deformed to take on square, triangular, honeycomb, dimer and different one-dimensional geometries. Using Bloch-Oscillations of a Fermi gas, we probe the bandstructure of this lattice for various configurations. In particular, we observe the appearance of Dirac points with tunable properties. When introducing a lattice anisotropy, two Dirac points approach each other and eventually anihilate. A band-gap can be created at the Dirac points by continously breaking the inversion symmetry of the system. Furthermore, we study how the effects of interactions change depending on the geometry of the lattice. We report on recent progress on using the dynamic tunability of the lattice as a method to study spin correlations in the system. [Preview Abstract] |
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K1.00108: Laser Spectroscopy of Rydberg Atoms in Deep Optical Lattices Yun-Jhih Chen, Georg Raithel We are constructing a new setup to investigate the spectroscopic studies of Rydberg atoms inside a deep optical lattice. Instead of counter-propagating laser beams, the new setup uses an optical resonator to produce the lattice. A 1064 nm lattice laser is focused at the center of a concentric cavity, which is composed of two spherical mirrors with high reflectivity. The laser intensity inside the cavity can be enhanced hundreds of times, so an optical lattice of 10 GHz deep can be realized with fairly low laser input. With the lattice depth in the GHz regime, we expect to see the rich structure of adiabatic Rydberg-atom trapping potentials, which correspond to highly mixed states. We will summarize the current stage of the experiment, including how we stabilize the concentric cavity and how it is integrated with the atom trapping apparatus. We will also present further details about how the laser spectroscopy in deep optical lattice can be achieved. [Preview Abstract] |
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K1.00109: Proposal to frustrated spin model in optical lattices Yanghao Chan, Emily Lichko, Luming Duan We propose a setup to generate next-nearest neighbor hoppings with the amplitude comparable to nearest neighbor hoppings in optical lattices. The effective model can be described as a frustrated spin model. We also study the phase diagram with the recently developed tensor network algorithm based on infinite projected entangled pair states (iPEPS). The simulation indicates a promising spin liquid phase in a finite parameter region, where magnetic of valence bond solid order vanish. [Preview Abstract] |
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K1.00110: A Next Generation Machine for Fermions in Optical Lattices Experiments Wujie Huang, Aviv Keshet, Edward Su, Christian Sanner, Jonathon Gillen, Wolfgang Ketterle We are building a new $^{23}$Na-$^{6}$Li machine for optical lattices experiments. Major experimental setups and upgrades will be described in details. We will also discuss how to reach the antiferromagnet regime and study quantum magnetism. [Preview Abstract] |
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K1.00111: Progress toward observation of AFM ordering of ultracold fermions in an optical lattice Russell A. Hart, Pedro M. Duarte, Tsung-Lin Yang, Randall G. Hulet We present progress toward the observation of antiferromagnetic (AFM) ordering of fermionic atoms in an optical lattice. We first laser cool on the $2S_{1/2}\rightarrow 2P_{3/2}$ transition and then further cool using the narrow $2S_{1/2}\rightarrow 3P_{3/2}$ transition to T $\sim$ 59 $\mu$K.\footnote{P. M. Duarte et al., Phys. Rev. A \textbf{84}, 061406 (2011).} The second stage of laser cooling greatly enhances loading to an optical dipole trap where a two spin state mixture of atoms is evaporatively cooled to degeneracy. We then adiabatically load $\sim$$10^{6}$ degenerate fermions into a 3D optical lattice formed by three orthogonal standing waves of 1064 nm light. Each of the three lattice beams is overlapped with a non-retrorelected green beam at 532 nm, which offsets the harmonic trapping caused by the lattice light. This offset can extend the number of lattice sites over which a Mott insulator phase can exist and facilitates evaporative cooling in the lattice. By adjusting the $s$-wave scattering length and the depth of the lattice, we tune the interaction and hopping terms of the Hubbard Hamiltonian. We will use Bragg scattering of light off of ordered spin planes to detect the AFM state.\footnote{T. A. Corcovilos et al., Phys. Rev. A \textbf{81}, 013415 (2010).} [Preview Abstract] |
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K1.00112: Generating strong artificial magnetic fields, spin-orbit coupling, and non-abelian gauge fields with few lasers Kaden Hazzard, Erich Mueller, Ana Maria Rey We propose an experimental scheme to generate strong gauge fields for atoms in an optical lattice, up to unit flux per plaquette, requiring fewer lasers than other proposals [1,2,3]. Like similar proposals [1,2], one generates a state-dependent lattice and couples adjacent sites with laser-induced tunneling. Our scheme, however, rectifies the resulting staggered magnetic flux to a homogeneous field using (experimentally feasible) ``stroboscopic'' time-dependent manipulation of the lattice lasers. One can generate sufficiently strong effective magnetic fields [U(1) gauge fields] to, for example, explore the interplay of fractional quantum Hall and lattice physics. For the case of alkaline earth atoms, the technique extends to generate SU(N) gauge fields, which are even richer. For example, simple homogeneous SU(2) gauge fields can be equivalent to spin-orbit coupling, which can host topological insulating phases even without interactions. \\[4pt] [1] D. Jaksch and P. Zoller, NJP 5, 56 (2003)\\[0pt] [2] F. Gerbier and J. Dalibard, NJP 12 033007 (2010)\\[0pt] [3] N. Cooper, PRL 106, 175301 (2011) [Preview Abstract] |
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K1.00113: Single-site resolved studies of a bilayer quantum degenerate gas Ruichao Ma, Philipp Preiss, Ming Tai, Waseem Bakr, Jonathan Simon, Markus Greiner Ultracold atoms in optical lattices are a versatile platform for quantum many-body simulation with the promise of insights into quantum magnetism, superconductivity, and superfluidity. In recent years, quantum gas microscopes with single-site resolution have opened the door to local observation and manipulation of strongly correlated two-dimensional quantum gases. Here we present techniques for extending study to two tunnel-coupled planes. Using an axial superlattice we prepare a bilayer system, with full control of the inter-plane tunnel coupling and detuning. We observe coherent inter-plane population transfer with single-site resolution in both planes. A collisional energy blockade in the bilayer system allows us to go beyond parity imaging and unambiguously identify site occupations from zero to three atoms. We have obtained site-resolved images of the ``wedding-cake'' Mott insulator structure and antiferromagnetic ordering in a quantum Ising model. Further applications include spin-dependent readout and in situ phase imaging. [Preview Abstract] |
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K1.00114: Dynamics of a Quasi-1D Bose Condensate in a Double Well Potential Intermediate Between the Tonks-Girardeau (TG) and Gross-Pitaevskii Regimes T. Bergeman, Zhedong Zhang Dunjko et al. [1] have shown how results of Lieb and Liniger [2] can be used to calculate the ground state of 1D bosons in a harmonic trap, for densities varying between the TG and GP regimes. Berman et al. [3] have shown that dramatic effects in the entropy occur in the transition between these regimes. As we are not aware of predictions for the dynamical behavior of quasi-1D Bose ensembles in double well potentials, we are attempting to adapt approaches of [4] to model oscillations through a barrier of varying height. Simple time-dependent GP equations reveal damping, but what happens at low density is not yet known.\\[4pt] [1] V. Dunjko, V. Lorent, and M. Olshanii, PRL 86, 5413 (2001).\\[0pt] [2] E. Lieb and W. Liniger, PR 130, 1605 (1963).\\[0pt] [3] G. P. Berman et al., PRL 92, 030404 (2004). \\[0pt] [4] R. Pezer and H. Buljan, PRL 98, 240403 (2007). [Preview Abstract] |
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K1.00115: Supersmectic, Superglass, and Spin-Glass Phases in Multimode cQED Alicia Kollar, Alexander Papageorge, Sarang Gopalakrishnan, Paul Goldbart, Benjamin Lev Investigations of many-body physics in an AMO context often employ a static optical lattice to create a periodic potential. Such systems, while capable of exploring, e.g., the Hubbard model, lack the fully emergent crystalline order found in solid state systems whose stiffness is not imposed externally, but arises dynamically. We propose an experiment to explore the spontaneous continuous symmetry breaking observed in compliant crystallization, and we aim to create an environment for the observation of effects pertinent to soft condensed matter systems including frustration and liquid crystalline topological defects concomitant with superfluidity. Off-resonantly pumping a BEC confined in a multimode cavity can induce a quantum version of the Brazovskii transition that arises in soft (classical) condensed matter contexts. The resultant supersmectic phase of intracavity atoms may suffer from sufficient global frustration to allow the formation of a superglass. Spin-glasses may also form due to cavity-mediated long-range, oscillatory, and frustrated spin-spin interactions. [Preview Abstract] |
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K1.00116: Quantum Dynamics of Solitons in Strongly Interacting Systems on Optical Lattices Chester Rubbo, Radha Balakrishnan, William Reinhardt, Indubala Satija, Ana Rey, Salvatore Manmana We present results of the quantum dynamics of solitons in XXZ spin-1/2 systems which in general can be derived from a system of spinless fermions or hard-core bosons (HCB) with nearest neighbor interaction on a lattice. A mean-field treatment using spin-coherent states revealed analytic solutions of both bright and dark solitons [1]. We take these solutions and apply a full quantum evolution using the adaptive time-dependent density matrix renormalization group method (adaptive t-DMRG), which takes into account the effect of strong correlations. We use local spin observables, correlations functions, and entanglement entropies as measures for the stability of these soliton solutions over the simulation times. \\[4pt] [1] R. Balakrishnan, I.I. Satija, and C.W. Clark, Phys. Rev. Lett. \textbf{103}, 230403 (2009). [Preview Abstract] |
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K1.00117: Few-body ultracold reactions in a Bose-Fermi mixtures Chen Zhang, Javier von Stecher, Chris H. Greene This project investigates the properties of fermionic molecule $^{87}\mbox{Rb} ^{40}\mbox{K}$, including (i) its formation from a mixed gas of bosonic $^{87}\mbox{Rb}$ and fermionic $^{40}\mbox{K}$ through magnetic field ramping and (ii) its scattering properties after formation. This has been approached mainly from the few body perspective: the spectrum of two bosons($^{87}\mbox{Rb}$) and two fermions($^{40}\mbox{K}$) is first calculated in a harmonic trap using correlated-Gaussian basis throughout the range of a broad Fano-Feshbach resonance. This provides a few-body solution to the magneto-association of fermionic Feshbach molecules, subsequently used to study the time-evolution of the system as the scattering length changes, mimicking experiments with Bose-Fermi mixture near Fano-Feshbach resonances. The structure of avoided crossings in the few-body spectrum enables an interpretation of the dynamics of the system as a sequence of Landau-Zener transitions. The calculated molecule formation rate is compared with experimental observations. Molecule-atom and molecule-molecule scattering properties are also discussed. [Preview Abstract] |
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K1.00118: Photoassociation of Rb atoms in an optical dipole trap Carlos Menegatti, Bruno Marangoni, Nadia Bouloufa, Olivier Dulieu, Luis Marcassa Laser cooling and trapping techniques are nowadays routinely used to produce atomic samples at temperatures around 1 mK or below. An old ambition in this research field is the direct application of such techniques to molecules, however due to the absence of closed optical transitions in molecules this is not straightforward. Nevertheless, cold and dense atomic trapped samples can be used to produce cold molecules trough photoassociation. In our experiment, we have trapped Rb atoms in a crossed broadband optical dipole trap. Our crossed beam configuration uses 25 W of power (at 1064 n, bandwidth of 2 nm) in each beam with about 50 micron waist radius at the focus and a depth of about 700 $\mu $K. In the typical condition, we have about 3 $\times $ 10$^{6}$ trapped atoms at a density of 3 $\times $ 10$^{12}$ cm$^{-3}$. We have observed that the Rb atom population presents a non-exponential decay in such a trap. We believe that such observation suggests that the sample is been photoassociated by the 1064 nm laser, forming an excited state Rb$_{2}$ molecule, which further decays forming Rb$_{2}$ in the ground state. The results are compared with a theoretical model. [Preview Abstract] |
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K1.00119: Photoassociative Spectroscopy of the (2)$^{3}\Pi$ State in RbCs Colin Bruzewicz, Mattias Gustavsson, Toshihiko Shimasaki, David DeMille We photoassociate RbCs molecules into several deeply-bound vibrational levels of the $\Omega=0^{+}$ and $\Omega=0^{-}$ components of the (2)$^{3}\Pi$ state. These include both previously observed and newly discovered levels. We measure the photoassociation laser intensity dependence of ground state molecule production for these levels and compare the saturation behavior to theoretical predictions. Using RKR analysis of the relevant molecular potentials, we have predicted and located a photoassociation state ((2)$^{3}\Pi_{0}$, $v=10$, $J=1$) that decays favorably to the $v=0$ vibrational level of the ground $X^{1}\Sigma^{+}$ state. This presents a promising pathway to the production of large numbers of rovibrational ground state polar molecules. [Preview Abstract] |
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K1.00120: Observation of Blue-Detuned Photoassociation to the 2 $(0_g^+)$ State of $^{85}$Rb$_2$ via REMPI Michael Bellos, Ryan Carollo, David Rahmlow, Jayita Banerjee, Matthew Bermudez, Edward Eyler, Phillip Gould, William Stwalley We report detection of photoassociation to vibrational levels blue of the $^{85}$Rb$_2$ $5s+ 5p_{1/2}$ asymptote, in the previously-unobserved 2 $(0_g^+)$ Hund's case (c) state that corresponds to 2 $^1 \Sigma _g^+$ in Hund's case (a). These excited-state ultracold molecules decay to the $a \, ^3 \Sigma _u^+$ state and are detected by pulsed REMPI through the 2 $^3 \Sigma _g^+$ state. We also observe, via trap loss, the 2 $(0_u^+)$, 2 $(0_g^-)$, and 2 $(1_g)$ states observed in [1], and confirm that these states are not the source of the observed molecules. Photoassociation through the observed levels of the 2 $(0_g^+)$ state populates vibrational levels approximately halfway up the $a \, ^3 \Sigma _u^+$ potential well. This pathway complements the blue-detuned photoassociation technique described in [2], which accesses the bottom of the $a$ state potential.\\[4pt] [1] R. A. Cline, J. D. Miller, and D. J. Heinzen, Phys. Rev. Lett. \textbf{73}, 632 (1994)\\[0pt] [2] M. A. Bellos, \emph{et. al.}, Phys. Chem. Chem. Phys. \textbf{13}, 18880 (2011) [Preview Abstract] |
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K1.00121: Quantum Mixtures of Ultracold Lithium and Ytterbium Atoms Alexander Khramov, Anders Hansen, William Dowd, Alan Jamison, Ben Plotkin-Swing, Ben Schwyn, Subhadeep Gupta Quantum mixtures of alkali and spin-singlet atoms offer new opportunities for studying few- and many-body physics, and also represent a starting point for producing paramagnetic polar molecules, of interest in various applications including quantum simulation and precision measurement. We report on studies of manipulating quantum mixtures of lithium (alkali) and ytterbium (spin-singlet) atoms by external magnetic fields. In one study, we achieve differential spatial control of the two atomic species by applying a magnetic gradient. Using this technique we are able to place bosonic $^{174}$Yb inside a deeply Fermi degenerate $^6$Li cloud as an interspecies probe. This gradient technique will also alleviate the relative gravitational sag for LiYb molecule formation work. In a separate study, we investigate the effect of $^{174}$Yb on Li$_2$ dimer formation and stability near the broad $^6$Li Feshbach resonance. The collisional stability of the Li-Yb mixture is adequate to allow time-resolved studies of these effects. We find evidence of modified Li$_2$ formation rate as well Li$_2$-Yb interactions. We will also report on studies of the Fermi-Fermi $^{173}$Yb-$^{6}$Li system and outline prospects for future work. [Preview Abstract] |
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K1.00122: Photoassociation of NaCs using chirped laser pulses Stephane Valladier I present rates of photoassociation of NaCs from the continuum of the $X^1\Sigma^+$ electronic state to a set of high-lying rovibrational states of the $A^1\Sigma^+$ electronic state using chirped laser pulses. Chirping the pulse encompasses several energies of the scattering atoms from the continuum of the $X^1\Sigma^+$ state, thus addressing the issue of the thermal distribution. This work is a stepping stone towards rovibrational cooling of NaCs using chirped laser pulses and stimulated Raman adiabatic passage. [Preview Abstract] |
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K1.00123: Dipole-dipole molecular scattering in electric and magnetic fields Goulven Qu\'em\'ener, John Bohn The scattering of two molecules is determined in free space by their inter-molecular potential. In cold and ultracold gases this interaction can be dominated by long-range dipole forces, which can be manipulated by electric and magnetic fields. We investigate the scattering of two molecules possessing both electric and magnetic dipole moments, taking OH molecules as an example, in the presence of an electric and a magnetic field with an arbitrary relative angle. We will compare the effect of these long-range interactions on the differential cross sections with the field-free case. We will discuss the possibility of changing differential cross sections by adjusting different combinations of fields. We will focus on collisions in the ultracold regime as well as in the cold regime ($T \sim 100$~mK). We will also discuss the fate of these collisions if they occur in an optical lattice. [Preview Abstract] |
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K1.00124: Light-assisted ion-neutral reactive processes in the cold regime: radiative molecule formation vs. charge exchange Olivier Dulieu, Felix J. Hall, Mireille Aymar, Nadia Bouloufa, Maurice Raoult, Stefan Willitsch We present a combined experimental and theoretical study of cold reactive collisions between lasercooled Ca$^+$ ions and Rb atoms in an ion-atom hybrid trap. We observe rich chemical dynamics which are interpreted in terms of non-adiabatic and radiative charge exchange as well as radiative molecule formation using high-level electronic structure calculations. We study the role of light-assisted processes and show that the efficiency of the dominant chemical pathways is considerably enhanced in excited reaction channels. Our results illustrate the importance of radiative and non-radiative processes for the cold chemistry occurring in ion-atom hybrid traps. [Preview Abstract] |
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K1.00125: Construction and characterization of tapered nano-fibers for hybrid quantum systems J.E. Hoffman, J.A. Grover, Z. Kim, J. Lee, K.D. Voigt, I.D. Schoch, A.K. Wood, J.R. Anderson, M. Hafezi, C.J. Lobb, L.A. Orozco, S.L. Rolston, J.M. Taylor, F.C. Wellstood, S. Ravets Nanofibers are a promising tool for hybrid systems of atomtronics and quantum information. We present the construction and characterization protocol that allows us to reliably produce nanofibers with a waist up to 10 cm in length and down to 500 nm in diameter operating around 780 nm (Rb D2 line). By controlling the angle in the tapered region at chosen radii, we can excite higher order modes in the fiber and observe their beating while monitoring the transmission during the pull. To reach the adiabatic regime, thus minimizing transmission losses in the fiber, we can reduce the taper angle in the critical excitation regions. Using this technique we can minimize the length of our taper region for given loss constraints. [Preview Abstract] |
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K1.00126: Loading a K dipole trap from a MOT Bruno Marangoni, Carlos Menegatti, Luis Marcassa We report the loading of a K crossed dipole trap directly from a regular K MOT. We start from a 300 $\mu $K MOT. In the sequence, we apply a molasses phase by varying the frequency and power of trapping and repumping beams, which allow us to cool the sample to 50 $\mu $K. Then the sample is loaded into a crossed broadband optical dipole trap. Our crossed beam configuration uses 25 W (at 1064 n, bandwidth of 2 nm) in each beam with about 50 micron waist radius of the focus and a depth of about 700 $\mu $K. In the final sample, we have about 2 x 10$^{6}$ atoms, a temperature of 10 $\mu $K and a trap lifetime of 200 ms. The sample will be used for cold molecule experiments. [Preview Abstract] |
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K1.00127: Advances in Bichromatic Force Slowing of Atoms and Molecules M.A. Chieda, E.E. Eyler The optical bichromatic force (BCF) holds promise as an efficient, simple, and compact means to slow atoms and molecules to MOT capture velocities.\footnote{M. Cashen and H. Metcalf, JOSA B \textbf{20}, 915 (2003).}$^,$\footnote{M. A. Chieda and E. E. Eyler, PRA \textbf{84}, 063401 (2011).} Metastable helium beams, with $v\sim1000$~m/s, are especially worthwhile atomic candidates since they presently require Zeeman slowers with lengths of 2--3~m. We present a novel BCF decelerator in which the Doppler shifts are chirped to keep the force centered on the atoms as they slow. This is made possible by recent advances in high-power diode lasers and electronics, and avoids many of the problems of alternative designs using large detunings. Initial tests on He* atoms show encouraging results. Unlike atoms, direct laser slowing of molecules remains exceedingly difficult, although success with SrF has very recently been reported.\footnote{J. F. Barry, E. S. Shuman, E. B. Norrgard, and D. DeMille, to be published.} We calculate that for molecules with near-cycling transitions, rapid laser BCF slowing should be possible.\footnote{Chieda, op. sit.} For the CaF molecule, we predict slowing by $\Delta v = 150$~m/s, enough to bring a buffer-gas cooled beam to rest. An experimental demonstration is in progress. [Preview Abstract] |
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K1.00128: A Rb D1 MOT for Simulating a SrF MOT Eric Norrgard, Toshihiko Shimasaki, John Barry, Colin Bruzewicz, Matt Steinecker, David DeMille Our group recently demonstrated transverse laser cooling and longitudinal laser slowing of a buffer-gas-cooled beam of polar molecules (SrF). Work is underway to load these slow molecules into a magneto-optical trap (MOT). A SrF molecular MOT presents a number of complications not present in a usual alkali MOT. The standard MOT design uses a cycling transition on the D2 line of an alkali. The level structure of SrF precludes the use of a true two-level cycling transition; instead, due to the existence of dark Zeeman sublevels, it is at first glance unclear whether a net trapping force can be applied. However, a closely analogous situation occurs in an alkali D1-line MOT, which has been experimentally demonstrated to be effective despite this level structure. This poster details ongoing investigations of a Rb D1 MOT, intended to better understand effects associated with this nonstandard level structure on the behavior of a MOT design, in particular when applied to SrF. [Preview Abstract] |
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K1.00129: Velocity Dependence of the Optical Force Produced by Adiabatic Rapid Passage Daniel Stack, John Elgin, Petr M. Anisimov, Harold Metcalf Adiabatic Rapid Passage (ARP) produces optical forces much larger than the ordinary radiative force, and is thought to work best when $\Omega_0 \sim \delta_0 \gg \omega_m \gg \gamma$, where $\Omega_0, ~ \delta_0,~ \omega_m, {\rm ~and~} \gamma$ are the Rabi frequency, sweep range, sweep rate, and natural decay rate respectively. We have observed strongly enhanced ARP forces on the 2$^3$S$_1 \rightarrow$ 2$^3$P$_2$ transition of He outside of this parameter range with our improved apparatus described previously.\footnote{D. Stack et al., Bull. Am. Phys. Soc. {\bf 56}, 153 (2011)} Our independent counter-propagating, chirped pulses allow greater freedom in the choice of relative beam parameters so we can detune the beams to simulate atomic motion. We will present our new data on the velocity dependence of the ARP force and compare these with our calculations.\footnote{D. Stack et al., Phys. Rev. A, {\bf 84}, 013420 (2011)} [Preview Abstract] |
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K1.00130: Toward a 2-D magneto-optical trap for polar molecules Matthew Hummon, Benjamin Stuhl, Mark Yeo, Alejandra Collopy, Jun Ye The additional structure that arises from the rotational degree of freedom in diatomic molecules makes difficult the adaptation of a traditional atomic magneto-optical trap (MOT) for use with molecules. We describe progress toward development of a 2-D MOT for laser cooled yttrium monoxide molecules based on a resonant LC baseball coil geometry. [Preview Abstract] |
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K1.00131: Transport coefficients for electrons in Hg vapor Sasa Dujko, Ron White, Zoran Petrovic Transport coefficients and distribution functions are calculated for electrons in Hg vapor under swarm conditions using a multi term theory for solving the Boltzmann equation, over a range of E/N values and temperatures relevant to lamp discharges. It is shown that for higher E/N the electron distribution is non-thermal for all Hg vapor temperatures considered, and that the speed distribution function significantly deviates from a Maxwellian under these conditions. Our work has been motivated, in part, by recent suggestions that highly accurate data for transport coefficients required as input in fluid models of Hg vapor lamp discharges may significantly improve the existing models. Current models of such lamps require a knowledge of the plasma electrical conductivity, which can be calculated from the cross sections for electron scattering in Hg vapor and mobility coefficients presented in this work. The effect of metastable atoms on the swarm parameters is also discussed. The influence of a magnetic field on electron transport coefficients in Hg vapor is investigated over a range of B/N values and angles between the fields. [Preview Abstract] |
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K1.00132: High order fluid model of streamer discharge in molecular nitrogen Sasa Dujko, Aram Markosyan, Ron White, Zoran Petrovic, Ute Ebert In this work, we present the basic elements of a theory developed for high order fluid modeling of streamer discharges. Using a momentum transfer theory, the first four moments of the Boltzmann equation are closed in the local mean energy approximation and coupled to the Poisson equation for space charge electric field. The high order pressure tensor appearing in the heat flux equation is specified in terms of previous moments. The average collision frequencies for momentum and energy relaxation and the average energy loses in inelastic collisions are calculated using the cross sections for electron scattering as input into a multi term Boltzmann equation solution. Negative streamer ionization fronts in nitrogen under normal conditions are investigated and it is shown that the high order fluid model involving the solution of the energy flux equation with the local mean energy approximation must be used in order to accurately simulate the streamer dynamics. [Preview Abstract] |
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K1.00133: FUNDAMENTAL SYMMETRIES AND PRECISION MEASUREMENTS II |
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K1.00134: Nuclear Spin-Dependent Parity Violation in Diatomic Molecules Jeffrey Ammon, Sidney Cahn, Emil Kirilov, David DeMille, Mikhail Kozlov, Richard Paolino Nuclear spin-dependent parity violation (NSD-PV) effects arise from exchange of the $Z^0$ boson (parametrized by the electroweak coupling constants $C_{2P,N})$ between electrons and the nucleus, and from the interaction of electrons with the nuclear anapole moment, a parity-odd magnetic moment. The latter scales with the nucleon number $A$ of the nucleus as $A^{3/2}$, while the $Z^0$ coupling is independent of $A$; the former will be the dominant source of NSD-PV in nuclei with $A$ greater than 20. NSD-PV effects can be dramatically amplified in diatomic molecules by bringing two levels of opposite parity close to degeneracy in a strong magnetic field. This opens the prospect for measurements across a broad range of nuclei. As a precursor to the measurement of the nuclear anapole moment of $^{137}Ba$, we have experimentally observed and characterized opposite-parity level crossings in $^{138}BaF$. These are found to be in excellent agreement with parameter-free predictions and indicate that the sensitivity necessary for NSD-PV measurements should be within reach. [Preview Abstract] |
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K1.00135: Testing gravity at the micro-scale with laser-cooled trapped microspheres David Atherton, Melanie Beck, Chris Thomas, Andrew Geraci In ultra-high vacuum, optically-trapped and cooled dielectric microspheres show great promise as force sensors. The environmental decoupling of their center-of-mass motion enables sub-attonewton sensitivity. Hence, they can be used to investigate Casimir forces or for testing non-Newtonian gravity [1]. We are developing an apparatus to trap and cool silica spheres in a combined optical dipole-cavity trap. The cavity will be filled with two laser fields to trap and cool the sphere center of mass motion, respectively. We describe our experimental results on optical trapping and cooling and our progress towards demonstrating the sensitivity of the technique. Ultimately, with a sphere trapped in an anti-node close to an end-mirror of the cavity, Casimir forces due to the end-mirror will be measured as a frequency shift of the oscillator. Non-Newtonian gravity-like forces will be tested by monitoring the displacement of the sphere as a mass is brought behind the cavity mirror. \\[4pt] [1] A.A.Geraci, S.B.Papp, and J.Kitching, Phys. Rev. Lett. 105, 101101 (2010). [Preview Abstract] |
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K1.00136: Progress toward a measurement of the electron's electric dipole moment using PbO Stephen Eckel, Paul Hamilton, Emil Kirilov, Hunter Smith, David DeMille Searches for permanent electric dipole moments (EDMs) of fundamental particles provide a way to detect new sources of time-reversal symmetry violation. We present recent results on an experiment to search for the electron's EDM, using the polar molecule PbO. PbO offers several advantages compared to atoms, including a much larger effective internal electric field ($>10$~GV/cm) and parity doubling, which can be used to reverse the effective internal electric field without reversing the laboratory electric field. This technique allows for significant rejection of systematic errors. Recent improvements to the experiment have resulted in statistical sensitivities of approximately $1 \times 10^{-27}\ e\mbox{cm}/\sqrt{\mbox{day}}$, which could allow for an improvement over the current experimental limit on the electron EDM in only a few days of integration time. Details of the approach and studies of possible systematic errors will be described. [Preview Abstract] |
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K1.00137: Proposed search for T-odd, P-even interactions in spectra of chaotic atoms with frequency combs Muir Morrison, Andrei Derevianko, M.G. Kozlov Violation of fundamental symmetries in atoms has been the subject of intense experimental and theoretical interest. P-odd, T-even transitions have been observed and are in excellent agreement with electroweak theory. Electron EDM searches have placed bounds on T-odd, P-odd interactions, constraining proposed extensions to the Standard Model. In this work we propose a search for T-odd, P-even (TOPE) interactions in atoms, which have thus far received little attention. We consider open-shell atoms (such as the rare earths) which have dense, chaotic excitation spectra with strong level repulsion. The strength of the level repulsion depends on the underlying symmetries of the atomic Hamiltonian. TOPE interactions lead to increased level repulsion. We will demonstrate how a statistical analysis of many chaotic spectra can determine the strength of level repulsion; in particular, the variance of the number of levels in an energy range has been shown to be a useful measure. We estimate that, using frequency comb spectroscopy, a sufficient number of chaotic levels could be measured to match or exceed the current experimental bounds on TOPE interactions. [Preview Abstract] |
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K1.00138: Progress towards an electron EDM measurement using trapped hafnium fluoride ions Matt Grau, Huanqian Loh, Eric A. Cornell Trapped molecular ions are an ideal platform for precision measurement of the electron electric dipole moment (eEDM). The low lying $^3\Delta_1$ electronic state of HfF$^+$ is predicted to contribute a large sensitivity enhancement to an eEDM measurement. We create HfF$^+$ by optically exciting a supersonic beam of HfF with two photons to an autoionizing state. We then load the HfF$^+$ into a novel Paul trap optimized for fluorescence collection and field uniformity. We report on recent experiments in the trap, and on our general progress towards the eEDM measurement. This work is funded by the National Science Foundation and the Marsico Endowed Chair. [Preview Abstract] |
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K1.00139: The ACME electron electric dipole moment experiment Brendon O'Leary, Cheong Chan, David Demille, John Doyle, Gerry Gabrielse, Paul Hess, Nick Hutzler, Emil Kirilov, Elizabeth Petrik, Ben Spaun The ACME collaboration is searching for the electron's electric dipole moment (eEDM) using a buffer gas-cooled beam of ThO molecules in their metastable H $^3\Delta_1$ state. We discuss details of the design, assembly, and current status of this experiment. We also describe progress towards potential future improvements in the signal-to-noise in future generations of ACME. [Preview Abstract] |
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K1.00140: ABSTRACT WITHDRAWN |
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K1.00141: Progress Toward a Two-Photon Optical Atomic Clock in Neutral Silver David McKenna, Carol Tanner Bender et al.\footnote{P. L. Bender et al., Bull. Am. Phys. Soc. 21, 599 (1976).} proposed Ag as an optical frequency standard. There are two narrow two-photon transitions 4d105s 2S1/2-4d95s2 2D5/2 (two 661nm photons) and 4d105s 2S1/2-4d95s2 2D3/2 (two 576nm photons) from the ground state. An advantage over single-photon optical clocks is that two equal counter-propagating photons will cancel the first order Doppler shift. The 4d95s2 2D3/2 state (width 4kHz) decays by two single photon emissions to the ground state via easily detectable photons at 338nm or 328nm. The 4d95s2 2D5/2 clock state is metastable (width\footnote{R. H. Garstang, J. Res. Natl. Bur. Stand. Sect. A 68, 61 (1964).} 0.8Hz) and decays via an electric quadrupole transition at 330.6nm. Our first goal is to observe excitation and decay of the 4d95s2 2D3/2 state in an atomic beam yielding optical frequencies for all hyperfine components in both 107, 109Ag. Our second goal is to observe excitation and decay of the clock state. We expect to achieve an atomic number density in the interaction region of 1010/cm3 at an oven temperature of $\sim$1300K. For a laser beam waist of 1cm, the transit-time-limited line width is $\sim$45kHz. One might expect a precision of $\sim$45Hz or 1/1013 in a measurement of the optical frequencies. [Preview Abstract] |
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K1.00142: Development of Al$^{+}$ optical clocks Jwo-Sy Chen, Kang-Kuen Ni, Chin-wen Chou, David J. Wineland, Till Rosenband Low sensitivity to electromagnetic fields and a narrow natural line width have enabled the $^{1}$S$_{0}$ -- $^{3}$P$_{0}$ transition in Al$^{+}$ to achieve 8.6 x 10$^{-18 }$accuracy. This allows for precise gravitational red-shift measurements with possible applications in geodesy, hydrology, and other fundamental tests of physics. However, the current laboratory system is not yet usable for these applications, due to the complexity of operation. We report recent progress towards the goals of higher accuracy and simplified non-laboratory operation of Al+ clocks. [Preview Abstract] |
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K1.00143: Test of Lorentz Invariance at the South Pole Using a Rotating Co-magnetometer Marc Smiciklas, Michael Romalis Among various experiments used to test Lorentz invariance, one of the most sensitive laboratory techniques is a measurement of nuclear spin-precession, descendant from the original Hughes and Drever experiments. In recent years, our rotating co-magnetometer has set the most stringent limits on vector and tensor Lorentz violation for fermions. A major limiting factor of spin-precession measurements is a large background signal due to the projection of the Earth's rotation onto the sensitive axis of the co-magnetometer, which also acts as a sensitive gyroscope. To greatly suppress this background, we present our plans to move the rotating co-magnetometer experiment to the South Pole Station, where the Earth's rotation direction and the direction of local gravity coincide. Rotating the co-magnetometer around this axis will eliminate any terrestrial background signals. We will present the latest results for the short-term sensitivity of the comagnetometer, which should enable an improvement of the current Lorentz-violation limits by three orders of magnitude at the South Pole. [Preview Abstract] |
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K1.00144: SPECIAL TOPICS (EXOTIC ATOMS AND MOLECULES; NONLINEAR DYNAMICS; NEW EXPERIMENTAL AND THEORETICAL METHODS; APPLICATIONS OF AMO SCIENCE) II |
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K1.00145: Magnetic Coil Design and Analysis Michael Bulatowicz Modified magnetic field coil geometries as described in U.S. Patent Applications US20100194506 and US20110247414 can produce substantially greater magnetic field homogeneity as compared to the traditional realized versions of idealized magnetic coil geometries such as spherical or Helmholtz. The new coil geometries will be described in detail and will be compared and contrasted to realized versions of idealized geometries, including discussion of errors not typically accounted for in traditional coil design and analysis. [Preview Abstract] |
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K1.00146: Positrons for Antihydrogen with ATRAP: efficient transfer of large positron numbers Cody Storry, Daniel Comeau, Asaf Dror, Daniel Fitzakerley, Matthew George, Eric Hessels, Matthew Weel Positrons accumulated in a room-temperature buffer-gas-cooled positron accumulator are efficiently transferred into a superconducting solenoid which houses the ATRAP cryogenic Penning trap for antihydrogen research. The positrons are guided along a 9-meter-long magnetic guide which connects the central field lines of the 0.15-tesla field in the positron accumulator to central magnetic field lines of the superconducting solenoid. Seventy independently-controllable electromagnets are required to overcome the fringing field of the large-bore superconducting solenoid. The guide includes both a 15 degree upward bend and a 105 degree downward bend to account for the orthogonal orientation of the accumulator with respect to the cryogenic Penning trap. Low-energy positrons ejected from the accumulator follow the magnetic field lines within the guide and are transferred into the superconducting solenoid with nearly 100{\%} efficiency. 7 meters of 5-cm-diameter stainless-steel tube, and a 20-mm-long, 1.5-mm-diameter cryogenic pumping restriction ensure that the 10$^{-2}$ mbar pressure in the accumulator is well isolated from the extreme vacuum required in the Penning trap to allow long antimatter storage times. [Preview Abstract] |
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K1.00147: Miniature, atomically referenced offset phase-locked laser for cold-atom sensors Juan Pino, Ben Luey, Sarah Bickman, Mike Anderson As ultracold atom sensors begin to see their way to the field, there is a growing need for small, accurate, and robust laser systems to cool and manipulate atoms for sensing applications such as magnetometers, gravimeters, atomic clocks and inertial sensing. In this poster we present an ultracompact, frequency agile laser source, referenced to a hyperfine transition of $^{87}$Rb. The laser system is housed in a package roughly the size of a stack of business cards, is hermetically sealed, and contains no moving parts -- ideal for field deployment. The laser system includes two lasers with independent temperature control, a Rb-filled vapor cell, a high-speed photodetector for monitoring the offset frequency between the lasers, as well the necessary optical isolation. We will present designs of the ultracompact laser system, as well as quantitative results including size, weight, expected power consumption, frequency agility, and frequency stability. [Preview Abstract] |
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K1.00148: Design and construction of tapered amplifier systems for the advanced undergraduate laboratory Jayampathi Kangara, Andrew Hachtel, Jason Barkeloo, Jeffrey Kleykamp, Matthew Gillette, Samir Bali We report on the design and construction of tapered amplifier (TA) systems in a primarily undergraduate setting, each system costing less than \$4000 to build. Plots of power output are presented versus seed power and TA current, including plots of TA output coupled through a single-mode optical fiber. We acknowledge invaluable discussions with Prof. D. Yavuz's group at Univ. of Wisconsin, Madison on the optics for collimation of the seed laser into the TA chip, and of the TA output. Also, we have based our current and temperature drivers for the TA system on circuit designs by Prof. D. Steck's group at the Univ. of Oregon, Eugene. [Preview Abstract] |
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K1.00149: Unitary Penning traps Joseph Tan, Samuel Brewer, Nicholas Guise We have constructed Penning traps in extremely compact forms, with unitary architectures that fully integrate NdFeB magnets (1.2 Tesla remnant magnetic field) within the electrode structure (occupying $< 150$ cm$^3$ assembled). A room-temperature apparatus has proven to be very useful in slowing and capturing ions extracted from an electron beam ion trap (EBIT).\footnote{J. N. Tan, S. M. Brewer, and N. D. Guise, to appear in \textit{Review of Scientific Instruments}} Here we present a two-magnet Penning trap designed to facilitate ion manipulation and optical experiments with stored ions. Some test results are presented. Experiments using this novel system are discussed in two presentations at this meeting.\footnote{N.D. Guise, \textit{et al.}, ``Charge exchange and spectroscopy with isolated highly-charged ions,'' at this meeting.}$^,$\footnote{S. M. Brewer, \textit{et al.}, ``Observing forbidden radiative decay of highly-charged ions in a compact Penning trap,'' at this meeting.} Unitary architecture can be particularly advantageous in small-instrument development (\textit{e.g.}, mass spectrometers) and in facilities or missions that have severe space constraints. [Preview Abstract] |
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K1.00150: Technique for Elimination of Excited States from Atomic and Molecular Ion Beams C.R. Vane, M.E. Bannister, C.C. Havener, Yuan Liu Fundamental interactions of atomic and molecular ions with electrons, neutral atoms and molecules, surfaces, and photons play major roles in many important plasma and chemical environments. Achieving a detailed understanding of these interactions is often complicated by the presence of uncharacterized populations of electronic or vibrational excited states, especially in making direct comparisons with theoretical predictions problematic. We are developing experimental techniques for reducing or eliminating ion source-generated excited states in atomic and molecular ion beams using a gas-filled RF quadrupole (RFQ) ion cooler, through natural radiative cooling during ion transit, and by preferential quenching in charge transfer collisions with selected buffer gases. Technical details and progress toward these goals will be presented. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy. [Preview Abstract] |
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K1.00151: 3 Watt CW OPO tunable 604nm to 616nm for quantum optics applications Angus Henderson, Thomas Halfmann, Simon Mieth A continuous wave optical parametric oscillator (CW OPO) pumped by a fiber laser has been developed which emits up to 3 Watts of single longitudinal mode radiation tunable in the wavelength range 604nm to 616nm. The device is a modified version of the ``Argos'' Model 2400 commercial product by Lockheed Martin Aculight. A 15 Watt 1064nm fiber laser pumps a CW OPO based upon periodically-poled Lithium Niobate (PPLN). A short section of the nonlinear crystal is poled to allow efficient intracavity sum frequency generation (SFG) between the OPO pump and signal wavelengths to generate orange radiation. The device can be coarsely tuned by matching the poling periods and temperature within the nonlinear crystal to phase-match both OPO and SFG processes simultaneously. Fine mode-hop-free tuning of the orange wavelength of up to 100GHz range can be achieved by applying a voltage to a PZT which tunes the pump laser. By similar intracavity conversion schemes, the system offers the potential of providing high power at wavelengths from 600nm to 1400nm in addition to the direct signal and idler wavelength ranges from 1400nm to 4630nm. Such capability comes without the complexity and reliability issues which are inherent in dye and Ti:Sapphire systems. Details of the OPO system performance and its use in quantum optics applications will be provided. [Preview Abstract] |
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K1.00152: ATTA Device for Measuring Trace Kr Contamination in Xenon Dark Matter Detectors Luke Goetzke, Tae Hyun Yoon, Andre Loose, Elena Aprile, Tanya Zelevinsky The XENON dark matter experiments search for low-energy elastic scattering events of Weakly Interacting Massive Particles (WIMPs) off Xe nuclei. For Xe targets and other noble liquids used in rare process searches, Kr contamination contributes background events through the beta decay of long-lived radioactive Kr-85. To achieve the sensitivity required of the next generation of dark matter detectors, the Kr contamination must be reduced to less than one part per trillion (ppt). We have developed an Atom Trap Trace Analysis (ATTA) device to measure Kr/Xe at the ppt level. Metastable Kr-84 is cooled and trapped in a magneto-optical trap, and imaged with a sensitive photodetector. Since Ar and Kr have similar wavelengths, the apparatus has been initially tested with Ar to avoid contamination. Results from tests with Ar and single atom detection with Kr will be presented. [Preview Abstract] |
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K1.00153: Progress Towards Room-Temperature Electron Spin Detection in Biological Systems Nicholas Chisholm, Igor Lovchinsky, Alex Sushkov, David Hunger, Alexey Akimov, Peggy Lo, Amy Sutton, Jacob Robinson, Norman Yao, Steven Bennett, Hongkun Park, Mikhail Lukin We report on recent progress of room-temperature electron spin sensing for biological applications using nitrogen-vacancy (NV) centers in diamond. Room-temperature detection of a small number of electron spins, situated outside the measurement substrate, has yet to be accomplished. Such an advance could lead to a number of applications, including detection of magnetic resonance signals from individual electron or nuclear spins of complex biological molecules, measurement of concentrations of radicals in living cells, and monitoring the ion channel function across cell membranes (important for exploring drug delivery mechanisms). Thus, the ability to measure magnetic fields with sensitivity allowing detection of a small number of electron spins with sub-micrometer resolution would be of major importance to the biological sciences. [Preview Abstract] |
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K1.00154: Generation of a green astro-comb using tapered photonic crystal fibers David Phillips, Alexander Glenday, Chih-Hao Li, Gabor Furesz, Nicholas Langellier, Matthew Webber, Guoqing Chang, Li-Jin Chen, Hung-Wen Chen, Jinkang Lim, Franz Kaertner, Andrew Szentgyorgyi, Ronald Walsworth Searches for exoplanets using precision stellar radial velocity (PRV) measurements are approaching Earth-like planet sensitivity. Astro-combs, which consist of a laser frequency comb, coherent wavelength shifting mechanism (such as a doubling crystal or photonic crystal fiber), and a mode-filtering Fabry-Perot cavity, provide a promising route to increased accuracy and long-term stability of the astrophysical spectrograph wavelength calibration.~To find an Earth-like exoplanet around a Sun-like star requires astro-combs that cover the visible spectral bands in which there is maximal stellar photon flux and rich high-quality spectral features for high-sensitivity PRV measurements. However, currently no comb lines are available directly from mode-lock lasers in the visible band. Here, we report generation of a green astro-comb from an octave spanning Ti:Sapphire laser, spectrally broadened by a custom tapered PCF to the visible band via fiber-optic Cherenkov radiation for frequency shifting, and filtered by a broadband Fabry-Perot cavity constructed by a pair of complementary chirped mirrors. [Preview Abstract] |
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K1.00155: Bioimaging Applications Using Color Centers in Diamond David Glenn, Huiliang Zhang, Anat Benado, Narayanan Kasthuri, Richard Schalek, Jeff Lichtman, Ronald Walsworth Color centers in diamond offer significant opportunities for the development of new techniques in bioimaging. We present recent work on the application of various color centers in nanodiamond as cathodoluminescent probes for efficient correlative microscopy. We also discuss progress on the use of bulk diamond samples with surface-implanted nitrogen-vacancy (NV) layers for magnetic field sensing, with the specific goal of making sensitive, spatially-localized measurements of free radical concentrations in biological systems. [Preview Abstract] |
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K1.00156: Adventures in Alignment-Based Magnetometry B. Patton, O.O. Versolato, E. Corsini, D.C. Hovde, S. Rochester, D. Budker Alkali-vapor magnetometers constitute the world's most precise magnetic sensors to date. Typically such devices employ circularly polarized light and thus rely upon orientation, the lowest-order polarization moment which can be excited in an alkali atom. The use of atomic alignment, imparted by linearly polarized light, can offer advantages over orientation-based magnetometry due to the higher-order symmetry of the aligned state. Here we discuss developments in alignment-based magnetometry, with particular focus on the issues of systematic errors such as heading error. Such errors will also be addressed in the context of a self-oscillating magnetometer, along with the prospect of completely remote magnetometry performed over a large free-space distance. [Preview Abstract] |
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