Bulletin of the American Physical Society
45th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 59, Number 8
Monday–Friday, June 2–6, 2014; Madison, Wisconsin
Session K1: Poster Session II (4:00pm - 6:00pm) |
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Room: Exhibit Hall |
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K1.00001: COLD ATOMS, MOLECULES AND PLASMAS |
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K1.00002: A Promising Candidate for Laser Cooling of Negative Ions: Observations of Bound-Bound Transitions in La$^{-}$ C.W. Walter, N.D. Gibson, D.J. Matyas, C.T. Crocker, K.A. Dungan, B.R. Matola, J. Rohl\'{e}n The negative ion of lanthanum, La$^{-}$, has been previously proposed as perhaps the best candidate of any atomic anion for laser cooling based on theoretical analysis [1]. In the present experiments, transitions between bound states of La$^{-}$ are investigated using tunable infrared photodetachment spectroscopy. The relative signal for neutral atom production was measured with a crossed ion-beam--laser-beam apparatus over the photon energy range 290--580 meV. The spectrum reveals at least ten sharp resonance peaks, some of which are interpreted as due to bound-bound electric dipole transitions in La$^{-}$ observed through resonant two-photon detachment. The richness of the observed bound state spectrum is unprecedented for atomic negative ions, and it highlights the unique properties of La$^{-}$ for applications such as laser cooling. \\[4pt] [1] S.M. O'Malley and D.R. Beck, \textit{Phys. Rev. A} \textbf{81}, 032503 (2010). [Preview Abstract] |
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K1.00003: Traveling-wave deceleration of ammonia Yomay Shyur, Noah Fitch, Heather Lewandowski Stark deceleration is a molecular beam manipulation technique where electric field gradients are used to produce a sample of cold polar molecules. Traditional pulsed Stark decelerators use digitally switched voltages in order to produce a time-averaged moving potential well to decelerate the molecules. The introduction of traveling-wave Stark decelerators presents a more efficient beam deceleration and trap loading method. By utilizing genuine moving three-dimensional potential wells, the traveling-wave Stark decelerator leads to greater number and density of trapped molecules. The dominant technical challenge to building a traveling-wave Stark decelerator is producing the high-voltage analog waveforms necessary to decelerate a molecular beam from a velocity of hundreds of m/s to rest. Our particular experiment requires 30 kV amplifiers capable of peak currents of 1.5 amps operating over a frequency range of 0-30 kHz. We report on our approach to this challenge and progress towards decelerating and trapping deuterated ammonia (ND$_{\mathrm{3}})$ from a supersonic beam using a traveling-wave Stark decelerator. [Preview Abstract] |
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K1.00004: Atom-trimer scattering lengths and four-body bound states for the one-dimensional ``HHHL'' system Connor Morehead, Nirav Mehta The energy spectrum and atom-trimer scattering length for a four-body system under one-dimensional confinement are presented. We consider an ``HHHL'' system of three heavy atoms and one light atom within the Born-Oppenheimer approximation with zero-range interactions. We present a ``phase-diagram'' on the $(m_H/m_L) - (a_{HH}/a_{HL})$ plane indicating the number of tetramer states and the sign of the atom-trimer scattering length. [Preview Abstract] |
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K1.00005: Millimeter wave spectroscopy of ultracold Rydberg atoms Vincent C. Gregoric, Thomas J. Carroll, Michael W. Noel An ultracold sample of highly-excited atoms can exchange energy through dipole-dipole interactions. We explore the use of millimeter wave spectroscopy as a tool for more precisely characterizing the dynamics of this energy exchange. [Preview Abstract] |
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K1.00006: Applications of Rydberg-dressing in few-body physics Jia Wang, Robin C\^{o}t\'{e} Using a laser far-detuned from a highly excited state, a ground state atom can be dressed by a small amount of Rydberg character. This technique is called Rydberg-dressing, which has attracted recent interest and was proposed to study many-body physics such as dipolar BEC, supersolid vortex crystals in BEC, and atomic Rydberg reservoirs for polar molecules. In this work, we apply Rydberg-dressing to the study of few-body physics. By using Rydberg-dressed interactions, ultracold chemical reactions can be manipulated and controlled. We also study the possibility of applying Rydberg-dressing to form a new kind of ``chemical bond'' and create ultra-long-range molecules. [Preview Abstract] |
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K1.00007: Phonon-mediated interactions and polaron formation of slow-light polaritons in a BEC Hanna-Lena Haug, Michael Fleischhauer We study the motion of dark-state polaritons (DSP) in a Bose-Einstein condensate. DSPs are formed in an atomic ensemble interacting in a $\Lambda$-type configuration with two light fields under conditions of electromagnetically induced transparency. In particular, we consider the ground-state atoms to form a BEC which can be well described by a macroscopic Gross-Pitaevskii wavefunction. Taking into account the interaction of pairs of ground-state atoms and between ground and spin-state atoms leads to the formation of polaronic quasi-particles consisting of DSPs and Bogoliubov phonons. In additon, the coupling to phonons results into a coupling between dark and bright-state polaritons as well as into phonon-mediated interactions between DSPs. [Preview Abstract] |
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K1.00008: Coupling a single electron to a BEC Robert L\"ow, Jonathan Balewski, Alexander Krupp, Anita Gaj, David Peter, Hans-Peter B\"uchler, Sebastian Hofferberth, Tilman Pfau For highly excited Rydberg atoms with principal quantum numbers n $\sim$ 40, single ground state atoms can be trapped in the potential created by the Rydberg electron, leading to so called trilobite Rydberg molecules. At even higher Rydberg states the depth of the interaction potential decreases, whereas the spatial extent of the Rydberg atom increases. For n in the range of 100-200 the electron orbit reaches the physical size of a Bose-Einstein condensate. At typical BEC densities, up to several ten thousand ground state atoms are now located inside one Rydberg atom, leading to a density dependent energy shift of the Rydberg state. This allows, together with the strong van-der-Waals blockade, to excite only one single Rydberg atom at a time in a condensate. We study the life time of this aggregates and the mechanical effect on the BEC. In the future we might be able to trap a full condensate inside one Rydberg atom or to image the Rydberg electron's wavefunction by its impact onto the superfluid. Nature 502, 664 (2013) [Preview Abstract] |
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K1.00009: Harmonically trapped two-atom systems: Interplay of short-range $s$-wave interaction and spin-orbit coupling X.Y. Yin, S. Gopalakrishnan, D. Blume We investigate the interplay between the single-particle spin-orbit coupling term of Rashba type and the short-range two-body $s$-wave interaction for cold atoms under external confinement. Treating the spin-orbit term with strength $k_{so}$ perturbatively, we determine the correction to the ground state energy for various parameter combinations. We find that the interplay between the spin-orbit coupling term and the $s$-wave interaction enters, depending on the exact parameter combinations of the $s$-wave scattering lengths, at order $k_{\textrm{so}}^2$ or $k_{\textrm{so}}^4$ for the ground state and leads to a shift of the energy of either sign. Additionally, we find that the spin-orbit coupling term turns, for certain parameter combinations, sharp crossings into avoided crossings with an energy splitting proportional to $k_{\textrm{so}}$. Our perturbative results are confirmed by numerical calculations that expand the eigenfunctions of the two-particle Hamiltonian in terms of basis functions that contain explicitly correlated Gaussians. [Preview Abstract] |
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K1.00010: The 2D Bose gas in box potential(s) Laura Corman, Lauriane Chomaz, Tom Bienaime, Christof Weitenberg, Remi Desbuquois, Sylvain Nascimbene, Jerome Beugnon, Jean Dalibard We will present our experiments with a 2D gas of bosons in box potentials with various geometries. The appearance of degeneracy in a 2D Bose gas is fundamentally different from the 3D case. We investigate the appearance of a bimodal distribution when the cloud is prepared in a flat bottom potential to test the relevance of the Berezinskii-Kosterlitz-Thouless mechanism with respect to the Bose-Einstein condensation mechanism. This measurement of degeneracy can then be confronted to the appearance of fringes when two similar systems interefere. Our technique also enables us to create various geometries for the clouds, helping to reveal vortices through interferometric measurement or short time-of-flight expansion. [Preview Abstract] |
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K1.00011: Behavior of a new type quantum accelerator mode in phase-modulated optical potential Wakun Lam, Sandro Wimberger, Siamak Dadras, Jiating Ni, Gil Summy Many efforts based on this model have been made in study of dynamical localization, quantum accelerator mode (QAM), to name but a few. QAM is a dynamical phenomenon in which the momentum of atoms exposed to a pulsed accelerating optical standing wave manifest linear growth. In many applications, we expect to improve the transport rate and suppress localization. A recent technique utilizing the phase modulation on the optical potential to produce transporting islands [PRE 68, 026209 (2003) and PRA 87, 013631 (2013)] has been discussed. In this presentation we study the stability of such islands in classical phase space of a modified DKR system in which the phase of the optical potential is modulated by a certain phase in each kick. Numerically simulations testify the existence of QAM even in small perturbation on the modulated phase. We also investigate the momentum distribution experimentally and numerically and report a new type of QAM which exposed in stationary optical potential instead. The interesting structure of the area of the transport islands against wide range of dynamical parameters in phase space is observed to be quite distinct to the regular one. [Preview Abstract] |
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K1.00012: Simple and efficient all-optical production of spinor condensates Jie Jiang, Lichao Zhao, Micah Webb, Yingmei Liu We present a simple and optimal experimental scheme for an all-optical production of a sodium spinor Bose-Einstein condensate (BEC). With this scheme, we demonstrate that the number of atoms in a pure BEC can be greatly boosted by a factor of 5 over some widely used schemes in a simple single-beam or crossed-beam optical trap. Our scheme avoids technical challenges associated with some all-optical BEC methods and may be applicable to other optically trappable atomic species. In addition, we discuss an upper limit for evaporative cooling efficiency in all-optical BEC approaches and a good agreement between our theoretical model and experimental data. [Preview Abstract] |
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K1.00013: 1D-3D Crossover in a Spin-Imbalanced Fermi Gas Melissa Revelle, Ben A. Olsen, Randall G. Hulet We have previously mapped the phase diagram of a 1D spin-imbalanced Fermi gas by confining lithium atoms in an array of tubes using a 2D optical lattice.\footnote{Y.A. Liao et al., Nature 467, 567 (2010).} Within each tube we observed separation of the atoms into a partially polarized superfluid core and fully paired or fully polarized wings (depending on the spin polarization). In 3D, the phase separation is inverted, such that the cloud center is fully paired.\footnote{G. B. Partridge et al., Science 311, 503 (2006); Y. Shin et al., Phys. Rev. Lett. 97, 030401 (2006).} We investigate the transition from a 1D to 3D gas by smoothly varying the lattice depth which changes the tunneling between the tubes. This allows us to study how the spin density changes as a function of inter-tube coupling. Progress will be reported. [Preview Abstract] |
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K1.00014: Transverse spin diffusion in ultracold fermionic potassium Stefan Trotzky, Chris Luciuk, Scott Beattie, William Cairncross, Alma Bardon, Joseph Thywissen This poster consolidates several measurements in our lab concerning the magnetization dynamics of fermionic potassium 40 at the Feshbach resonance for the two lowest-energy hyperfine states. Our experiment begins with a completely polarized gas in the $F=9/2$, $m=-9/2$ state. Dynamics are initiated with a ``superposition quench,'' in which each atom is put in an equal superposition of resonant eigenstates. Over the next several milliseconds, the gas demagnetizes due to the combined effect of an external gradient and diffusive spin currents. We observe four essential effects: (1) Spin diffusivity is close to $\hbar$ divided by the atomic mass, which is roughly what one would expect for quasiparticles whose lifetime is $\hbar$ divided by the Fermi energy; (2) A second Fermi surface is formed, and eventually equilibrates with the majority Fermi surface, resulting in an increase in entropy and temperature; (3) The contact parameter grows from zero to a steady-state value consistent with equilibrium; and (4) The spin current precesses around the local magnetization. [Preview Abstract] |
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K1.00015: Quantum Degenerate Strontium in a 3D Optical Lattice J.A. Aman, B.J. Desalvo, T.C. Killian We present our experiments with quantum degenerate neutral strontium in a 3-D optical lattice formed with 532nm light. Precision control and manipulation of quantum degenerate gases in optical lattices allows for the realization and investigation of tunable many-body systems. Strontium, in particular, has been studied extensively in optical lattices due to the narrow $5s^2\:^1S_0 \rightarrow \:5s5p\:^3P_j$ transitions for use as an atomic clock. However, in the present work, we take advantage of these narrow transitions together with strontium's unique isotopic properties to investigate interaction regimes inaccessible to alkali atoms. Among the topics we plan to explore are formation of ultracold molecules using an optical Feshbach resonance as well as the effects of dissipation on atom dynamics. [Preview Abstract] |
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K1.00016: Ytterbium optical lattice clock with $10^{-18}$ level characterization Nathaniel Phillips, Jeff Sherman, Kyle Beloy, Nathan Hinkley, Marco Schioppo, Chris Oates, Andrew Ludlow A recent comparison of two ytterbium-based optical lattice clocks at NIST demonstrated record stability of $1.6$ parts in $10^{18}$ after 25,000s averaging. We report on measurements of the two primary systematic effects that shift the ultra-narrow clock transition, towards a reduction of the clock uncertainty to the $10^{-18}$ level. Uncertainty stemming from the blackbody radiation (BBR) shift is largely due to imprecise knowledge of the thermal environment surrounding the atoms. We detail the construction and operation of an in-vacuum, thermally-regulated radiation shield, which permits laser cooling and trapping while enabling an absolute temperature measurement with $<20$~mK precision. Additionally, while operation of the optical lattice at the magic wavelength ($\lambda_{\rm m}$) cancels the scalar Stark shift (since both clock states shift equally), higher-order vector and two-photon hyperpolarizability shifts remain. To evaluate these effects, as well as the polarizability away from $\lambda_{\rm m}$, we implement a lattice buildup cavity around the atoms. The resulting twenty-fold enhancement of the lattice intensity provides a significant lever arm for precise measurement of these effects. [Preview Abstract] |
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K1.00017: ABSTRACT WITHDRAWN |
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K1.00018: Low Noise Trapping and High Resolution Imaging of Fermions in an Optical Lattice Anton Mazurenko, Florian Huber, Maxwell F. Parsons, Christie S. Chiu, Sebastian Blatt, Markus Greiner Single-site resolved imaging of fermions in an optical lattice is an area of interest due to the possibility of probing highly entangled many-body states with high fidelity. We will apply this technique to problems in condensed matter physics, such as ordering in magnetic systems and quantum phase transitions. We have successfully trapped fermionic 6-Li atoms in an optical lattice 10 micron below a high-quality reference surface. This surface is part of a high resolution imaging system (numerical aperture 0.85) including an interferometrically aligned commercial microscope objective. Trapping atoms in this configuration presents novel challenges and we have developed a highly stable optical lattice (-130 dBc relative intensity noise), that can be dynamically controlled over three orders of magnitude in intensity, with maximum trap frequency of 1 MHz. We have also developed a system for Raman state manipulation within this lattice. We have explored heating rates and lifetimes in this configuration and report the results. [Preview Abstract] |
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K1.00019: Novel Techniques for Control and Detection of Ultracold Quantum Gases Logan W. Clark, Li-Chung Ha, Eric L. Hazlett, Cheng Chin We report on the progress of three novel techniques for studying ultracold quantum gases. First, we discuss our technique for measuring the structure factor of a 2D quantum gas and our progress towards using such measurements to perform local detection of thermodynamic quantities in the gas. Second, in order to create a flat potential or any other arbitrary potential, we explore the use of a high resolution objective to project a blue detuned laser onto the gas. By spatially patterning the laser with a digital micromirror device we create arbitrary optical potentials with $\sim$1 $\mu$m resolution. In addition, we report a general method to modify the band structure in an optical lattice by shaking the lattice. Condensates in the lattice can form domains with long-range ferromagnetic order. [Preview Abstract] |
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K1.00020: Canceling spin exchange interaction in a spin-1 Bose-Einstein condensate via magnetic pulses Huanbin Li, Wenxian Zhang Spin exchange interaction between atoms in a spin-1 Bose condensate causes atomic spin evolve periodically under the single spatial mode approximation. By applying fast magnetic pulses, we find analytically that the effect of the spin exchange interaction is effectively canceled, i.e., the atomic spin is frozen, for certain initial states. Numerical calculations with and without single mode approximation are carried out to confirm the validity of the analytical predictions. [Preview Abstract] |
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K1.00021: On the stability of a Floquet Bose-Einstein condensate in a one-dimensional optical lattice Sayan Choudhury, Erich Mueller Motivated by recent experimental observations (C.V. Parker {\it et al.}, Nature Physics, {\bf 9}, 769 (2013)), we analyze the stability of a Bose-Einstein condensate (BEC) in an one-dimensional lattice subjected to periodic shaking. In such a system there is no thermodynamic ground state, but there may be a long-lived steady-state, described as an eigenstate of a ``Floquet Hamiltonian.'' We calculate how scattering processes lead to a decay of the Floquet state. We map out the phase diagram of the system and find regions where the BEC is stable and regions where the BEC is unstable. We show that Parker et al. perform their experiment in the stable region, which accounts for the long life-time of the condensate ($\sim$ 1 second). We also estimate the scattering rate of the bosons in the region where the BEC is unstable. [Preview Abstract] |
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K1.00022: Quenching a Bose-condensate to unitarity: transients, steady states, and novel singularities Kaden Hazzard, Andrew Koller, John Corson, Andrew Sykes, Jose D'Incao, Chris Greene, Ana Maria Rey, John Bohn Motivated by recent experiments [1], we study the dynamics of a three-dimensional Bose gas following a sudden quench of the scattering length from zero to unitarity. We show that essential features of the time-evolution of the momentum distribution $n(k)$ can be captured with two simple approaches: an analytic two-body calculation and a numerical time-dependent variational ansatz for the many-body state. Although both approaches can capture the growth and oscillations of $n(k)$ as a function of time for short times and large $k$, only the variational approach predicts the formation of a steady state for large-momentum observables, where $n(k)$ approaches a time-independent function. We report the appearance of a short-distance (large-momentum) singularity that is absent in equilibrium. We incorporate the physics governing particle loss through a three-body calculation. Consistent with experiments, we predict lifetimes which are long compared to the dynamics of large momentum modes. \\[4pt] [1] Makotyn \textit{et al.}, Nature Physics \textbf{10}, 116-119 (2014) [Preview Abstract] |
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K1.00023: Quantum dynamics of spinor Bose gas in quasi-1D potentials Chih-Yuan Huang, Chun-Chia Chen, Keng-Shiao Wu, Ming-Shien Chang Interacting quantum particles confined in a low-dimensional trap often can lead to strong correlation between the constituent particles due to the combined effects of restricted motional degrees of freedom and quantum fluctuations. In this work we present our studies on the quantum dynamics of a spinor Bose condensate in a 2D array of quasi-1D tubular potentials formed by a 2D optical lattice. Our experiment started with producing a $^{87}$Rb spin-1 Bose-Einstein condensates (BEC) in a crossed optical dipole trap (XODT), and following that the condensate was further loaded into a 2D optical lattice superimposed on the XODT. In this configuration quantum phase transition between superfluid and insulator states was observed in the 2D lattice plane. When the XODT was suddenly switched off in the insulator state, the bose gas oscillated in the quasi-1D tubes, and analyses showed that the clouds were in either the Thomas-Fermi or Tonks-Girardeau regimes, depending on the density of the clouds. We will report our most recent results on spinor condensates in quasi-1D tubes and outline our future direction. [Preview Abstract] |
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K1.00024: Low-field Feshbach resonances in dysprosium Kristian Baumann, Nathaniel Burdick, Mingwu Lu, Benjamin Lev We report the observation [1] of resonance-like loss in the trap population of ultracold dysprosium as a function of magnetic field, which we attribute to anisotropy-induced Feshbach resonances arising from Dy's large magnetic dipole moment and nonzero electronic orbital angular momentum. We recorded these resonances for four different isotopes, three bosonic and one fermionic, over a field range of 0-6 G and show that the number of resonances changes significantly as a function of temperature, even in the nK regime. Most of the observed resonances are of very narrow width. The fermionic isotope, unlike its bosonic counterparts, possesses nonzero nuclear spin and exhibits a much higher density of resonances. \\[4pt] [1] K. Baumann, N. Q. Burdick, M. Lu, and B. L. Lev, to appear in Phys. Rev. A, Rapid Communications (2013). arXiv:1312.6401 [Preview Abstract] |
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K1.00025: Universal three-body physics in two dimensions and quasi-two dimensions Jose P. D'Incao, Brett D. Esry In this work we explore the three-body problem in two and quasi-two dimensions using the adiabatic hyperspherical representation. We developed the formalism in terms of the hyperangular democratic coordinates and determine several symmetry properties and boundary conditions. We explore the existence of purely two dimensional (2D) three-body bound states and their connections with the quasi-two dimensional case (Q2D). We also explore three-body confinement-induced resonances as well as the physics related to three-dimensional Efimov physics when transitioning to a Q2D geometry, illustrating experimental signatures of such effect relevant for Q2D ultracold quantum gases with strong interactions. Supported by AFOSR-MURI. [Preview Abstract] |
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K1.00026: Three spinors with long-range van der Waals interactions --- quantitative predictions for ultracold collisions Yujun Wang, Paul S. Julienne We perform three-body calculations for ultracold alkali atoms with multichannel spinor physics built in. By using van der Waals interaction models and allowing each atom to carry spin states, the observed three-body resonant features in ultracold Cs experiments [1] can be well reproduced in our calculations. In particular, we construct two-level and three-level spinor models for each atom, which are adequate for describing three-body physics near isolated Feshbach resonances and strongly overlapping resonances, respectively. The Efimov-related three-body features we reproduce are located near Feshbach resonances with vastly different resonance strengths, and typically have non-negligible shifts from the universal positions predicted for infinitely broad Feshbach resonances. The simplicity of our model, although remarkable in predicting the a new class of universal positions for three-body features, still leaves some nonuniversal signature in their overall magnitude. We discuss the physics behind such properties and the scenarios where nonuniversal aspects can be important. \\[4pt] [1] Kraemer, et al., Nature 440, 315 (2006); S. Knoop, et al., Nature Phys. 5, 227 (2009); F. Ferlaino, et al., Few-Body Sys. 51, 113 (2011). [Preview Abstract] |
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K1.00027: An Experimental Apparatus for Studying Rydberg-Rydberg Interactions in Quantum Degenerate Gases of Strontium Francisco Camargo, Roger Ding, James Aman, Xinyue Zhang, Joseph Whalen, Robert Fields, F. Barry Dunning, Thomas Killian We discuss the design and construction of a new apparatus for creating and studying long-range interactions in ultracold gases of strontium by exploiting Rydberg states, either through their direct excitation or through laser-induced Rydberg dressing. Strontium features one fermionic ($^{\mathrm{87}}$Sr) and three bosonic ($^{\mathrm{84}}$Sr, $^{\mathrm{86}}$Sr, $^{\mathrm{88}}$Sr) isotopes, all of which have been brought to quantum degeneracy. It also possesses singlet and triplet Rydberg states that furnish a wide variety of attractive and repulsive interactions. ~Furthermore, strontium Rydberg atoms feature an optically active core electron which can be used to manipulate and detect Rydberg atoms. These features make strontium a promising system for studying interactions in ultracold Rydberg gases. [Preview Abstract] |
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K1.00028: Rydberg spectroscopy of trapped Holmium atoms James Hostetter, Thomas Schmid, Luke Stuyvenberg, Mark Saffman Holmium atoms have the potential for collective encoding of multi-qubit quantum registers in a large manifold of 128 hyperfine/Zeeman ground states. We report on studies of optical pumping of laser cooled and optically trapped Ho atoms to the $|F,M\rangle=|11,0\rangle$ or $|F,M\rangle=|11,11\rangle$ ground states. Two-photon Rydberg excitation using near degenerate 410.5 and 415 nm beams has minimal Doppler broadening. Progress towards Rydberg spectroscopy using the optically pumped sample will be presented. [Preview Abstract] |
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K1.00029: A Study of the Laser Cooling Potential of the ARP Force John Elgin, James Dragan, Harold Metcalf Adiabatic Rapid Passage (ARP) is used to produce optical forces much stronger than the radiative force.\footnote{D. Stack et al., Phys. Rev. A {\bf 84} 013420 (2011)} It works best when $\Omega_0 \sim \delta_0 \gg \omega_m \gg \gamma$, where $\Omega_0$, $\delta_0$, $\omega_m$, and $\gamma$ are the Rabi frequency, sweep range, sweep rate, and the spontaneous emission rate respectively. However, ARP has been shown to work in the parameter range of $\Omega_0 \sim \delta_0 \sim \omega_m$. We have now found that the force is stronger when the center frequency of the laser sweep is detuned from atomic resonance by an amount that is comparable to $\omega_m$, and this too is beyond the normal parameter range. Other observations have shown that the strength of the force is strongly dependent on the shape and characteristics of the modulated pulses. By investigating these effects we are working towards using ARP for laser cooling, by studying the force's velocity dependence in the $2^3$S$_1 \rightarrow$ 2$^3$P$_2$ transition in He. [Preview Abstract] |
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K1.00030: Subwavelength Localization of Atomic Excitation Using Electromagnetically Induced Transparency Jared Miles, Diptaranjan Das, Zach Simmons, Deniz Yavuz The diffraction limit sets a minimum size for regions that can be resolved or addressed using light. We demonstrate an experiment where excitation of atoms to a specific hyperfine level is confined to small regions $\sim$100nm, about 8 times smaller than the excitation wavelength. The experiment is performed using 87Rb atoms trapped in an optical dipole trap and utilizes $\sim$100ns EIT pulses. The technique uses the nonlinear power dependence of EIT to coherently transfer atoms only near the nodes of a standing wave. Increasing the standing wave intensity can produce vanishingly small low-intensity areas about the nodes and as a result atomic transfer only occurs in these small areas. Since regions smaller than the diffraction limit cannot be directly imaged, confirmation of narrowing is provided by an autocorrelation measurement technique. [Preview Abstract] |
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K1.00031: Cooling Strontium in a Narrow Line Magneto-Optical Trap B.J. Reschovsky, D.S. Barker, N.C. Pisenti, G.K. Campbell We describe the behavior and performance of a magneto-optical trap (MOT) operating on the narrow ($\Gamma/2 \pi = 7.4$ kHz) $^1$S$_0$ - $^3$P$_1$ transition of strontium. We have successfully trapped multiple strontium isotopes at temperatures of less than 1 $\mu$K. These cold samples are then transferred to a pancake-shaped optical trap where they are evaporatively cooled to quantum degeneracy. [Preview Abstract] |
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K1.00032: Collisions of dipolar particles in a two-dimensional trap and a tilted field Goulven Qu\'em\'ener, Maxence Lepers, Olivier Dulieu We present the two-body collisional properties of ultracold dipolar particles (magnetic polar atoms or electric polar molecules) in a two dimensional confinement, in the presence of a tilted magnetic or electric field with respect to the confining axis. We employ a time-independent quantum formalism using a frame transformation between spherical coordinates which represent the dipole-dipole interaction and cylindrical coordinates which represent the confining potential. Here the tilted field mixes different components m$_l$ of the partial waves. We will present elastic and loss rates for both bosonic and fermionic particles as a function of the induced dipole moment, the confinement strength, and the tilted angle of the field. [Preview Abstract] |
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K1.00033: Buffer-gas loaded MOTs for Ho, Yb,Tm, and Er Eunmi Chae, Garrett Drayna, Boerge Hemmerling, Nick Hutzler, Aakash Ravi, Alejandra Collopy, Matthew Hummon, Benjamin Stuhl, Mark Yeo, Jun Ye, John Doyle We report on direct loading of lanthanide atoms into MOTs from a two-stage slow buffer-gas beam source, which has a peak forward velocity of $\sim$ 30 - 60 m/s [1], considerably lower than other beam implementations. The low velocity combined with species generality makes this source useful for loading magneto-optical traps (MOTs), especially for species that are not well suited to the traditional approach of oven plus Zeeman slower. We report loading MOTs with Yb, Tm, Er, and Ho, without any additional slowing stages. Application of a single frequency slowing laser to the buffer-gas beam of Yb results in an unprecedentedly high loading rate of $2.0(1.0) \times 10^{10}$ Yb atoms/s and $1.3(0.7)\times 10^8$ Yb atoms in the MOT [2]. We plan to use this versatile source to load a MOT with CaF, following the same general approach to that used with YO and SrF [3, 4].\\[4pt] [1] N. R. Hutzler, et al., Chem. Rev. 112, 4803 (2012).\\[0pt] [2] B. Hemmerling, et al., arXiv:1310.3239.\\[0pt] [3] M. T. Hummon, et al., Phys. Rev. Lett. 110, 143001 (2013).\\[0pt] [4] E. F. Shuman, et al., Nature 467, 820 (2010). [Preview Abstract] |
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K1.00034: Experiments with an ultracold Na and Rb mixture Dajun Wang, Fudong Wang, Xiaoke Li, Xiaodong He, Bing Zhu, Jun Chen, Mingyang Guo Na and 87Rb are two of the most popular atoms for ultracold physics research. Their mixture, which has been investigated little previously, is also of great interest for many different applications. We are especially interested in the possibility of producing ground-state ultracold polar molecules with a large dipole moment and stable against two-body reactions by association of these two atoms. Here, I will present our recent progress in this direction, including the first production of a double BEC of Na and Rb atoms and the study of their interspecies magnetic Feshbach resonances. Recent progress in producing NaRb Feshbach molecules will also be discussed. [Preview Abstract] |
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K1.00035: Topological preparation of Laughlin and Pfaffian states of photons Fabian Grusdt, Fabian Letscher, Mohammad Hafezi, Michael Fleischhauer We present a new scheme for the preparation of highly correlated Laughlin and Pfaffian states of photons. In contrast to other proposals we do not start from an $N$-photon Fock state, but adiabatically introduce photons one by one. As a consequence our scheme only requires a time $T \sim N$ to grow an $N$-photon Laughlin state. We consider a realistic setup of two-dimensional cavity arrays subject to an effective magnetic field. Moreover we assume strong on-site interactions for photons. Our scheme makes use of the quantization of the Hall current, which is topologically protected, and the ability to manipulate the magnetic flux locally in photonic systems [Hafezi, arXiv:1310.7946]. By adiabatically introducing flux quanta in the center of an $N$-photon Laughlin state, quasihole excitations can be created. Replenishing the resulting hole with a new photon allows to create an incompressible $N+1$ photon Laughlin state. Photon-losses lead to an increasing number of hole-type excitations at the edge of the Laughlin liquid and thus limit the achievable system-sizes. We present numerical simulations for small systems of interacting photons and for an effective model of non-interacting composite fermions, demonstrating the feasibility of our scheme. [Preview Abstract] |
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K1.00036: Transport behaviors of BEC in synthetic spin-orbit and gauge fields Robert Niffenegger, Chuan-Hsun Li, Abraham Olson, Yong P. Chen We experimentally study transport of Bose Einstein Condensates (BECs) with synthetic gauge fields and spin-orbit coupling (SOC), created by counter propagating Raman lasers which couple hyperfine spin and momentum states of $^{87}Rb$ and generate a synthetic dressed bandstructure modifying atoms' kinetic energy-momentum dispersion. We have developed various techniques to actuate and control the transport with synthetic electric fields and spin-dependent fields, as well as by gravity (the direction of our spin-momentum coupling) and far off resonance lasers. We study the time evolution of the momentum, spin and density (measured after time-of-flight) of BEC during transport in the dressed bands, both with and without the optical trap. [Preview Abstract] |
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K1.00037: Excitation of a quantum gas to Rydberg states Thibault Vogt, JingShan Han, Ruixiang Guo, Wenhui Li Rydberg atoms constitute a paradigmatic system for the study of quantum many-body physics. Very large dipole-dipole interaction between Rydberg atoms leads to the dipole blockade, at the heart of promising proposals for quantum simulation or studies of strongly correlated systems [1-2]. Dipole blockade has already been used to excite spatially organized structures of Rydberg atoms [3], realize single photon sources [4] or implement quantum gates [5]. In this talk, I will present the recent developments of our experimental setup for achieving highly coherent Rydberg excitation. I will also discuss our progress on the detection of Rydberg atoms, with preliminary spectroscopic measurements obtained for the excitation of Rydberg atoms in a nearly degenerate gas of 87Rb atoms. \\[4pt] [1] Weimer, H., et al. Nature Physics 6: 382-388 (2010).\\[0pt] [2] Pupillo, G., et al. PRL 104 223002 (2010). \\[0pt] [3] Schausz, P., et al. Nature 491 87-91 (2012). \\[0pt] [4] Peyronel et al. Nature 488 58-60 (2012).\\[0pt] [5] Isenhower et al. PRL 104 010503 (2010). [Preview Abstract] |
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K1.00038: ATOMIC AND MOLECULAR COLLISIONS |
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K1.00039: Model-Free Measurement of the Excited-State Fraction in a $^{85}$Rb Magneto-Optical Trap Hai Nguyen, Goga Veshapedze, Chris Verzani, Charles Fehrenbach, Jeng Bang, Brett DePaola In many experiments involving magneto-optical traps (MOTs), it is imperative to know the fraction of atoms left in an excited state by the cooling and trapping lasers. In most cases, researchers have used formulas that were derived for simple 2-level systems interacting with a single beam of light having a well-defined polarization, and in the absence of magnetic or electric fields. However a MOT environment is much more complex than this. Here we directly measure the excited fraction in a MOT of $^{85}$Rb atoms in a model-independent manner for a wide range of trapping conditions. We then fit our measured fractions to an ansatz based on a simple model. Knowing only the trapping laser's total intensity and detuning from resonance, one can then use this ansatz to accurately predict the excited fraction. The work is a companion piece to similar measurements on a MOT of $^{87}$Rb. [Preview Abstract] |
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K1.00040: Absolute rate coefficient for the recombination of W$^{18+}$ ions with electrons: Storage-ring experiment and theoretical calculations K. Spruck, N.R. Badnell, C. Krantz, A. Becker, D. Bernhardt, M. Grieser, M. Hahn, O. Novotn\'y, R. Repnow, D.W. Savin, A. Wolf, A. M\"{u}ller, S. Schippers Within the general effort to provide reliable atomic data for the modeling of fusion plasmas we have experimentally measured and theoretically calculated the rate coefficient for electron-ion recombination of bariumlike W$^{18+}$ ions forming lathanumlike W$^{17+}$. At low electron-ion collision energies, the rate coefficient is dominated by strong, mutually overlapping recombination resonances. In the temperature range where the fractional abundance is expected to peak in a fusion plasma, the experimentally derived recombination rate coefficient is a factor of about 400 larger than the rate coefficient which is currently recommended for plasma modeling. The extraordinary complexity of the atomic structure of the open-4f system under study makes the theoretical calculations extremely demanding. Nevertheless, the theoretical results agree reasonably well with the experimental findings, which puts confidence into the ability of the theoretical method to generate reasonably accurate atomic data also for other complex ions. [Preview Abstract] |
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K1.00041: Rotationally inelastic collisions of He and Ar with NaK: Theory and Experiment K. Richter, T. Price, J. Jones, C. Faust, A.P. Hickman, J. Huennekens, R.F. Malenda, A.J. Ross, P. Crozet Rotationally inelastic collisions of NaK ($A\,^1\Sigma^+$) molecules with He and Ar have been studied. At Lehigh, we use a pump-probe scheme (the probe is scanned over transitions to the $3\,^1\Pi$ state) with either polarization labeling (PL) or laser-induced fluorescence (LIF) spectroscopy. At Lyon, one-laser excitation is used with Fourier Transform (FT) fluorescence spectroscopy. In both cases, the pump laser excites a particular ro-vibrational level $A\,^1\Sigma^+$($v, J$). We observe strong direct lines corresponding to transitions from the ($v, J$) level pumped, and weak satellite lines corresponding to transitions from collisionally-populated levels ($v, J^{\prime} = J + \Delta J$). The ratios of satellite to direct line intensities in LIF and PL yield information about population and orientation transfer. A strong propensity for $\Delta J =$ even transitions is observed for both He and Ar perturbers. In the FT fluorescence experiment we also observe $v$ changing collisions. Theoretical calculations are also underway for collisions in both the $A\,^1\Sigma^+$ and $X\,^1\Sigma^+$ states. For He-NaK we have calculated potential surfaces using GAMESS and carried out coupled channel scattering calculations of transfer of population, orientation, and alignment. [Preview Abstract] |
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K1.00042: Electron Impact Excitation Cross Sections for Mg V Swaraj Tayal, A. Sossah Improved and extensive electron impact excitation cross sections calculations for fine-structure transitions have been performed using the B-spline Breit-Pauli R-matrix method. The flexible non-orthogonal sets of spectroscopic and correlation radial functions are employed for an accurate representation of the target states and scattering functions. The close-coupling expansion includes 92 bound levels covering all possible terms of the ground $2s^22p^4$ and excited $2s2p^5$, $2p^6$, $2s^22p^33s$, $2s^22p^33p$, $2s^22p^33d$, and $2s2p^43s$ configurations. The calculated excitation energies of the target levels are in excellent agreement with experiment and represent an improvement over the previous calculations. The present results of cross sections are compared with a variety of other close-coupling and distorted-wave calculations. The oscillator strengths and cross sections are in good agreement with other theories and available experimental data. [Preview Abstract] |
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K1.00043: Electron Impact Excitation Collision Strengths for Fine-Structure Transitions in of Fe IX Swaraj Tayal, Oleg Zatsarinny New extensive calculations are performed for electron collision strengths and transitions probabilities for a wide range of transitions in Fe IX. The collision strengths are calculated in the close-coupling approximation using the B-spline Breit-Pauli R-matrix method. The multiconfiguration Hartree-Fock method in conjunction with B-spline expansions is employed for an accurate representation of the target wave-functions. The close-coupling expansion includes 370 fine-structure levels of Fe IX in energy region up to $3p^55s$ states. It includes levels of the $3p^6$, $3p^53d,4l,5s$, $3s3p^63d,4s,4p$, $3p^43d^2$, $3s3p^53d^2$ configurations and some low-lying levels of the $3p^33d^3$ configuration. The effective collision strengths are obtained by averaging the electron collision strengths over a Maxwellian distribution of velocities at electron temperatures in the range from 10$^4$ to 10$^7$ K. There is a good agreement with the previous R-matrix calculation for transitions between first 17 levels of the $3p^6$, $3p^53d$ and $3s3p^63d$ configurations. The present results considerably expand the existing data sets for Fe IX, allowing more detailed treatment of the available measured spectra from different space observatories. [Preview Abstract] |
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K1.00044: A full-dimensional study of H2+H2 collisions: coupled-states versus close-coupling formulation Robert C. Forrey, Alex Bohr, Stephen Paolini, N. Balakrishnan, P.C. Stancil Kinetic models often require a complete set of rate coefficients for H$_2$+H$_2$ collisions in order to interpret results from spectroscopic observations or to make quantitative predictions. Recent progress in full-dimensional quantum dynamics using the numerically exact close-coupling (CC) formulation has provided good agreement with existing experimental data for low-lying states of H$_2$ and increased the number of state-to-state cross sections that may be reliably determined over a broad range of energies. Nevertheless, there exist many possible initial states (e.g. states with high rotational excitation) that still remain elusive from a computational standpoint even at relatively low collision energies. In these cases,the coupled-states (CS) approximation offers an alternative full-dimensional formulation. We assess the accuracy of the CS approximation for H$_2$+H$_2$ collisions by comparison with benchmark results obtained using the CC formulation. The results are used to provide insight into the orientation effects of the various internal energy transfer mechanisms. A statistical CS approximation is also investigated and cross sections are reported for transitions which would otherwise be impractical to compute. [Preview Abstract] |
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K1.00045: Formation of heavy-Rydberg ion-pair states in Rydberg atom collisions with attaching targets Changhao Wang, Michael Kelley, Sitti Buathong, F. Barry Dunning Electron transfer in collisions between K($n$p)Rydberg atoms and electron attaching molecules can lead to formation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair orbiting at large internuclear separations. In the present work ion-pair states are created in a small collision cell and allowed to exit into an analysis region where their binding energy and velocity distributions are determined with the aid of electric-field-induced dissociation and a position sensitive detector. Ion pair production is analyzed using a Monte Carlo collision code that models both the initial Rydberg electron capture and the subsequent behavior of the product ion pair. The data demonstrate that collisions with SF$_{6}$ and CCl$_{4}$ lead to formation of long-lived ion pair states with a broad distribution of binding energies whose velocity distribution is strongly peaked in the forward direction. [Preview Abstract] |
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K1.00046: Exploring dipole blockade using high-$n$ strontium Rydberg atoms Xinyue Zhang, Shuzhen Ye, F. Barry Dunning, Moritz Hiller, Shuhei Yoshida, Joachim Burgd\"{o}rfer Studies of the production of strongly-polarized quasi-1D high-$n$, $n\sim300$, strontium ``$n$F" Rydberg states in an atomic beam by three-photon excitation in a weak dc field suggest that (in the absence of blockade effects) densities of $\sim10^6 $ $cm^{-3}$ might be achieved. At such densities the interparticle separation, $\sim100$ $\mu m$, becomes comparable to that at which dipole blockade effects are expected to become important. Apparatus modifications are underway to allow the exploration of blockade at very high-$n$ and the effects of the high energy level density. Blockade is also being examined through calculations of the energy spectrum for two interaction atoms. Access to the blockade regime promises creation of Rydberg atoms at well-defined separations whose interactions can be coherently controlled using electric field pulses thereby enabling study of the dynamics of strongly-coupled Rydberg systems. [Preview Abstract] |
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K1.00047: Li$_{2}$~-- Li reactive collisions at high initial j Mark Rosenberry, Ramesh Marhatta, Brian Stewart Inelastic~molecular collisions are a fundamental process in astronomy and chemistry.~ We are studying collisions of~$^{7}$Li$_{2}$~with~$^{7}$Li in a heat pipe oven, and looking for nuclear parity-changing events that signal a chemical reaction.~ Previous work in our group studied such reactions for low initial j; we are now working to collect data for the case of high initial j, where quasi-resonant phenomena occur.~ We have also incorporated new corrections for multiple collisions in our analysis.~ Quasi-classical trajectory calculations are used to model these reactions and extract physical insight.~ [Preview Abstract] |
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K1.00048: Metastable Oxygen Production by Electron-Impact of Oxygen Jeffrey Hein, Paul Johnson, Isik Kanik, Charles Malone Electron-impact excitation processes involving atomic and molecular oxygen are important in atmospheric interactions. The production of long-lived metastable O($^1$S) and O($^1$D) through electron impact of atomic O and molecular O$_2$ play a significant role in the dynamics of oxygen-containing atmospheres (Earth, Europa, Io). Emissions from metastable O ($^1$S $\rightarrow$ $^1$D) produce the well-recognized green light from terrestrial aurora. Electron-impact excitation to $^1$S and $^1$D are sensitive channels for determining energy partitioning and dynamics from space weather. Electron-impact excitation cross sections determined through fundamental experimental studies are necessary for modeling of natural phenomena and observation data. The detection of metastable states in laboratory experiments requires a novel approach, since typical detection techniques (e.g., fluorescence by radiative de-excitation) cannot be performed due to the long-lived nature of the excited species. In this work, metastable O is produced through electron impact, and is incident on a cryogenically cooled rare gas matrix. The excimer production and subsequent rapid radiative de-excitation provides measurable signal that is directly related to the originating electron-impact excitation process [Preview Abstract] |
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K1.00049: Studying inelastic collisions of H$_{2}$ and D$_{2}$ by means of ultrasonic experiments Jesus Perez-Rios, Salvador Montero An explicit formulation for the rotation-translation relaxation time in terms of state-to-state rate coefficients associated to inelastic collisions is presented. The formulation provides a tangible link between acoustic and gas dynamics, and quantum scattering calculations. The state-to-state rates needed for the detailed interpretation of relaxation of H$_{2}$ and D$_{2}$, including isotopic variant mixtures, have been calculated by solving the close-coupled Schr{\"o}dinger equations. Relaxation related quantities (rotational cross section, bulk viscosity, relaxation time, and collision number) calculated from first principles agree reasonably well with acoustic absorption experimental data on H$_{2}$ and D$_{2}$ well below 293 K. This result confirms the proposed formulation, the quantum scattering calculations, and the potential energy surface employed. [Preview Abstract] |
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K1.00050: Radiative association cross sections J.F. Babb, B. Zygelman Radiative association is a binary collisional process where atomic, molecular, or ionic species collide and form a molecular complex through emission of a photon. We survey some of the advantages and disadvantages of existing theoretical methodologies and explore procedures for rapid evaluation of cross sections. Applications to ultra-cold atoms and ions and to astrophysics are described. [Preview Abstract] |
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K1.00051: Modification of fine-structure collisional transfer cross sections in dense noble buffer gases Alina Gearba, Jerry Sell, Randy Knize We will present measurements of collisional fine-structure transfer between rubidium 5P states in Rb-He-Ar and Rb-He-Xe gas mixtures. The Rb-He mixing rates are significantly increased by the addition of Ar or Xe buffer gases, even though the Rb-He mixing cross section is orders of magnitude larger than those of Rb-Ar or Rb-Xe. We explain this effect due to three-body collisions which alter the Rb 5P fine-structure splitting and can be understood from the Rb-noble gas interatomic potentials. These results are generalized for fine-structure transfer in dense gases involving other excited states and atoms. [Preview Abstract] |
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K1.00052: Noble Gas Polarimetry Using Rb EPR Frequency Shifts Z.L. Ma, K. Jeong, E. Houghtby, T. Paskvan, M.E. Limes, B. Saam EPR frequency shifts of optically polarized alkali-metal atoms can be exploited for polarimetry of noble-gas nuclei polarized by spin-exchange optical pumping. Our group recently measured the enhancement factor $\kappa_0 = 493$ for Rb-$^{129}$Xe [1], which characterizes the electron wave-function overlap during collisions and is crucial to the calibration of the frequency-shift for $^{129}$Xe polarimetry. This type of polarimetry is useful in several applications involving optically polarized $^{129}$Xe; our particular motivation is an ${\it in\ situ}$ measurement of absolute $^{129}$Xe polarization within the optical pumping cell of a flow-through $^{129}$Xe polarizer [2]. This application has some particular challenges, and we have initially observed some unexpected shifts in the $^{87}$Rb EPR frequency measurement on board the polarizer. In effort to disentangle these apparent systematic effects, we have constructed a separate experiment to characterize Rb EPR shifts for both $^{3}$He and $^{129}$Xe in sealed cells. We present results and analysis of these experiments and discuss implications for using this method in flow-through polarizers.\\[4pt] [1] Z. L. Ma, et al., Phys. Rev. Lett., 106, 193005 (2011).\\[0pt] [2] I. Ruset et. al., Phys. Rev. Lett., 96. 053002 (2006). [Preview Abstract] |
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K1.00053: Optical Control of Population Flow between Molecular Electronic States of Different Spin Multiplicity Ergin Ahmed, Xinhua Pan, John Huennekens, Marjatta Lyyra The adiabatic description of molecular electronic states in terms of potential energy surfaces, defined by the motion of the electrons, on which the slower nuclear motions (vibrations and rotations) occur, breaks down when relativistic effects such as the coupling between the electron spin and its orbital angular momenta (spin-orbit coupling) are taken into account. The result is that conical intersections (avoided crossings) develop between the adiabatic potential surfaces (curves) resulting in molecular states with mixed spin (multiplicity) character. Such intersections play a critical role in defining the pathways of nonadiabatic processes such as collisional quenching and intersystem crossings of excited states. In this work we demonstrate optical control of the singlet/triplet probability distribution in the outcome of a collisional process between Lithium dimers and Argon atoms. The control is achieved using the Autler-Townes effect to manipulate the spin character of a spin-orbit coupled pair of levels serving as a ``gateway'' between the singlet and triplet electronic state manifolds. [Preview Abstract] |
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K1.00054: Application of Polarization effects in the initial state and the Screening Potential in the final state to the ionization of helium by electron impact Haripada Saha We will report the results of our investigation on the ionization of atoms by electron impact using our recently extended MCHF theory of electron impact ionization of atoms [1]. The triple differential cross sections for electron impact ionization of helium atom will be calculated for 70.6 eV incident electron energy. The Multiconfiguration Hartree-Fock method for continuum electron wave function will be used to calculate polarization of the helium target by the incident electron. The effect of electron correlation between the two final state continuum electrons will be approximated by the variationally determined screening potential [2-3]. The excess electron energy will be shared equally and unequally by the two final state continuum electrons. The results will be compared with the experimental and accurate theoretical calculations [4].\\[4pt] [1] Hari P. Saha, (unpublished).\\[0pt] [2] M.R.H. Rudge, Rev. Mod. Phys. 40, 564 (1968).\\[0pt] [3] C.Pan and A.F Starace, Phys. Rev. Lett. 67, 185 (1991); Phys. Rev. A45, 4588 (1992).\\[0pt] [4] Ren et al., Phys. Rev. A 83, 052711 (2011). [Preview Abstract] |
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K1.00055: Out-of-plane ($e,2e$) measurements with 150eV incident beam energy on He autoionizing levels N.L.S. Martin, B.A. deHarak In previous work we reported out-of-scattering-plane $(e,2e)$ measurements and calculations for helium $2\ell2\ell'$ auto\-ionizing levels at 488eV incident electron energy and scattering angle 20.5$^\circ$. The results were presented as $(e,2e)$ angular distributions energy-integrated over each level\footnote{B.A. deHarak, K. Bartschat, and N.L.S. Martin, Phys. Rev. Lett. {\bf 100}, 063201 (2008)} and the detailed energy dependence of the recoil/binary peak ratio\footnote{B. A. deHarak, K. Bartschat, and N.L.S. Martin, Phys. Rev. A {\bf 89}, 012702 (2014)}. We have now begun similar measurements at 150eV electron beam energy and scattering angle 39.2$^\circ$. The geometry is then the same as for the earlier high energy experiments: ejected electrons are detected in a plane that contains the momentum transfer direction and is perpendicular to the scattering plane. The momentum transfer is 2.1~a.u., which is the same as in the earlier experiments. We will present preliminary data and compare the angular distributions with the high energy results. [Preview Abstract] |
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K1.00056: Laser assisted free-free scattering: a test of the Kroll-Watson approximation for different targets B.A. deHarak, N.L.S. Martin In previous work we reported on experiments that examined electron-helium scattering in the presence of an Nd:YAG laser field of 1.17 eV photons. We tested the Kroll-Watson approximation (KWA)\footnote{N. M. Kroll and K. M. Watson, Phys. Rev. A 8, 804 (1973)} for one photon emission, over a range of incident electron energies 50~eV $\to$ 350~eV at fixed laser polarization,\footnote{B. A. deHarak, L. Ladino, K. B. MacAdam and N. L. S. Martin, Phys. Rev. A {\bf 83}, 022706 (2011)} and also the for the effect of varying the laser polarization direction within a plane perpendicular to the scattering plane.\footnote{http://meetings.aps.org/link/BAPS.2013.DAMOP.D1.150} Both these experiments were in good agreement with the KWA. We are currently carrying out measurements of one, two, and three photon absorption, in three different targets, He, Ar, and N$_2$. The KWA predicts that the results should be target independent, since the approximation assumes negligible photon-target interaction. We will present the results of experiments carried out at different incident electron energies. [Preview Abstract] |
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K1.00057: B-spline R-matrix with pseudostates calculations for electron collisions with atomic nitrogen Yang Wang, Oleg Zatsarinny, Klaus Bartschat The \hbox{{\it B}-spline} \hbox{{\it R}-matrix} (BSR) with pseudo\-states method~[1] is employed to treat electron collisions with nitrogen atoms. Predictions for elastic scattering, excitation, and ionization are presented for incident energies between threshold and about 100~eV. The largest scattering model included 690 coupled states, most of which were pseudostates that simulate the effect of the high-lying Rydberg spectrum and, most importantly, the ionization continuum on the results for transitions between the discrete physical states of interest. Similar to our recent work on e-C collisions~[2], this effect is particularly strong at ``intermediate'' incident energies of a few times the ionization threshold. Predictions from a number of collision models will be compared with each other and the very limited information currently available in the literature. Estimates for ionization cross sections will also be provided.\\[4pt] [1] O. Zatsarinny and K. Bartschat, J. Phys. B~{\bf 46} (2013) 112001.\\[0pt] [2] Y. Wang, O. Zatsarinny, and K. Bartschat, Phys. Rev. A~{\bf 87} (2013) 012704. [Preview Abstract] |
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K1.00058: Electron collisions with cesium atoms -- benchmark calculations and application to modeling an excimer-pumped \hbox{alkali} laser Oleg Zatsarinny, Klaus Bartschat, Natalia Babaeva, Mark Kushner The {\it B}-spline {\it R}-matrix (BSR) with pseudo\-states method~[1] was employed to describe electron collisions with cesium atoms. Over 300 states were kept in the close-coupling expansion, including a large number of pseudo\-states to model the effect of the Rydberg spectrum and, most importantly, the ionization continuum on the results for transitions between the discrete physical states of interest. Predictions for elastic scattering, excitation, and ionization will be presented for incident energies up to 200~eV and compared to results from previous calculations~[2,3] and available experimental data. The results of our calculations were used to model plasma formation in the excimer-pumped alkali laser, XPAL, operating on the Cs$\,\rm (6^2P_{3/2,1/2} \to (6^2S_{1/2})$ (852$\,$nm and 894$\,$nm) transitions. At sufficiently high operating temperature, pump power, and repetition rate, plasma formation in excess of $\rm 10^{14}-10^{15}\,cm^{-3}$ occurs. This may reduce laser output power by electron collisional mixing of the upper and lower laser levels.\\[4pt] [1]~O.~Zatsarinny and K.~Bartschat, J.~Phys.~B~{\bf 46} (2013) 112001.\\[0pt] [2]~K.~Bartschat and Y.~Fang, Phys.~Rev.~A {\bf 62} (2000) 052719.\\[0pt] [3]~O.~Zatsarinny and K.~Bartschat, Phys.~Rev.~A {\bf 77} (2008) 062701. [Preview Abstract] |
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K1.00059: Electron-impact excitation of xenon John B. Boffard, R.O. Jung, L.W. Anderson, Chun C. Lin Xenon electron-impact cross sections are used in the analysis of non-invasive optical emission spectroscopy diagnostics of many xenon plasmas including Hall thrusters. We present measurements of optical emission cross sections as a function of incident electron energy (0-200 eV) for a large number of emission lines in the 250-900 nm wavelength range using a mono-energetic electron beam along with monchromator/PMT detector. The selection of measured cross sections include both excitation into higher neutral levels, and simultaneous ionization/excitation into Xe$^+$, Xe$^{2+}$, and Xe$^{3+}$ levels. Measurements were performed at a low pressure to minimize pressure effects often observed in xenon measurements due to radiation trapping of resonant emission lines [1].\\[4pt] [1] J. T. Fons and C. C. Lin, Phys. Rev. A \textbf{58}, 4603 (1998). [Preview Abstract] |
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K1.00060: Bare- and dressed-ion collisions from neon atoms studied within a nonperturbative mean-field approach Gerald Schenk, Tom Kirchner Motivated by the availability of new experimental data [1] we study electron removal processes in collisions of neon atoms with doubly- and triply-charged bare and dressed ions in the 25 keV/u to 1 MeV/u impact energy regime. The many-electron problem is represented by a single mean field, which in the case of dressed-ion impact includes the projectile electrons. Moreover, the same basis is used to propagate all active orbitals thereby ensuring orthogonality at all times and allowing for a final-state analysis in terms of standard Slater determinantal wave functions. The same approach was used in a recent work for B$^{2+}$-Ne collisions [2], in which we examined the role of the projectile electrons for target-recoil-charge-state production. The present study expands on that work in several respects: (i) additional collision channels are considered; (ii) time-dependent response is taken into account; (iii) comparisons with equicharged bare ions are carried out in order to shed more light on the role of the (active and passive) projectile electrons.\\[4pt] [1] W. Wolff \textit{et al.}, Phys. Rev. A \textbf{84}, 042704 (2011); J. S. Ihani \textit{et al.}, J. Phys. B \textbf{46}, 115208 (2013).\\[0pt] [2] G. Schenk \textit{et al.}, Phys. Rev. A \textbf{88} 012712 (2013). [Preview Abstract] |
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K1.00061: Time-dependent density functional theory study of correlation in proton-helium collisions Matthew Baxter, Tom Kirchner A recent model to describe electron correlations in time-dependent density functional theory (TDDFT) studies of antiproton-helium collisions [1] is extended to deal with positively charged projectiles. The main complication is that a positively-charged projectile can capture electrons in addition to ionizing them to the continuum. As a consequence, within the TDDFT framework one needs to consider three, instead of just one, correlation integrals ($I_c$s) when formally expressing the probabilities for the occurring one- and two-electron processes in terms of the density. We discuss possible extensions of an adiabatic model for $I_c$ [2] to deal with this situation and present results for few keV to few MeV proton-helium collisions obtained from basis-generator-method calculations with microscopic response effects included [3].\\[4pt] [1] M. Baxter and T. Kirchner, Phys. Rev. A \textbf{87}, 062507 (2013).\\[0pt] [2] F. Wilken and D. Bauer, Phys. Rev. Lett. \textbf{97}, 203001 (2006).\\[0pt] [3] M. Keim \textit{et al.}, Nucl. Instr. and Meth. B \textbf{233}, 240 (2005). [Preview Abstract] |
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K1.00062: Characterization of a Compact Cylindrically Symmetric Micro-Mott Polarimeter Nathan Clayburn, Evan Brunkow, George Rutherford, Timothy Gay A Mott polarimeter measures electron spin by determining the left-right counting rate asymmetry, $A$, for Mott scattering from a high-Z target. This value of $A$ is non-zero for spin states perpendicular to the electron scattering plane. Recently, a variety of small, spherically symmetric polarimeters of the ``concentric'' electrode design using energies of $\sim$ 20 keV have been designed and constructed [1]. The geometry of these polarimeters causes inelastic scattering events to be largely eliminated electrostatically which results in a resolution higher than that obtainable with energy-sensitive detectors alone [2]. A small quasi-cylindrically-symmetric polarimeter, simpler in conception and construction than its spherical counterparts, has been designed and built [3]. Using a new negative electron affinity GaAs polarized electron source, this compact Mott polarimeter's efficiency has been determined and its Sherman function has been estimated. \\[4pt] [1] T. J. Gay, Adv. At. Mol. Phys. \textbf{57}, 227-232 (2009).\\[0pt] [2] G. D. Fletcher, T. J. Gay and M. S. Lubell, Phys. Rev. A \textbf{34}, 911 (1986).\\[0pt] [3] G. H. Rutherford, R. M. King, G. G. Shepard, M. S. Zimmerle, Bull. Am. Phys. Soc. \textbf{44} (1999). [Preview Abstract] |
(Author Not Attending)
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K1.00063: Reduction of Helicity-Dependent Instrumental Laser Intensity Asymmetries Samantha Burtwistle, Joan Dreiling, Timothy Gay We present a new optical system that greatly reduces helicity-dependent instrumental intensity asymmetries. The optical setup is similar to that described in Fabrikant \textit{et al.} [1], where two beams with orthogonal linear polarizations are sent through a chopper, allowing only one beam to pass through the optical system at a time. The two temporally-separated beams are then spatially recombined. We now use a system, with a second active polarization changing element, that is analogous to that described in Gay and Dunning [2], which compensates for false asymmetries in Mott polarimetry. In our setup, the orthogonal linear polarizations are now circularly polarized by a Pockels cell switching between a retardance of $+\lambda $/4 and --$\lambda $/4 at the same frequency as the chopper, but with a 90-degree phase shift. Using this method, we have been able to control the standard deviation of the mean of our asymmetries, as measured by a photodiode with lock-in signal processing, to 3*10$^{-8}$. \\[4pt] [1] M.I. Fabrikant, K.W. Trantham, V.M. Andrianarijaona, and T.J. Gay, Appl. Opt.~\textbf{47}, 2465-2469 (2008).\\[0pt] [2] T.J. Gay and F.B. Dunning, Rev. Sci. Instrum.~\textbf{63}, 1635 (1992). [Preview Abstract] |
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K1.00064: Three-body recombination of helium atoms from ultracold to thermal energies: classical trajectory vs. quantal calculations Jesus Perez-Rios, Steve Ragole, Jia Wang, Chris H. Greene A general method to study classical scattering in $n$-dimensions is developed. Through classical trajectory calculations the new method is applied to compute the three-body recombination rate as a function of the collision energy for helium atoms, as an example. Quantum calculations are also performed for the $J^{\Pi}$ = $0^{+}$ symmetry of the three-body recombination rate in order to compare with the classical results, yielding good agreement for $E\sim$ 1 K. The classical threshold law is derived and numerically confirmed for the three-body recombination rate. Finally, a relationship is found between the quantum and classical three-body elastic cross section which exhibits a similarity to the well-known shadow scattering in two-body collisions.\\[4pt] [1] J. P\'{e}rez-R\'{i}os et al., J. Chem. Phys. {\bf 140}, 044307 (2014). [Preview Abstract] |
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K1.00065: HYBRID Q SYSTEMS |
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K1.00066: Harnessing vacuum forces for quantum sensing of graphene motion Christine Muschik, Simon Moulieras, Adrian Bachtold, Frank Koppens, Maciej Lewenstein, Darrick Chang Vacuum forces are one of the most spectacular predictions of quantum physics and have gained great importance in modern nanotechnology, due to their large magnitude at nanoscale distances. We present a novel method to exploit the strength of vacuum forces associated with single quantum emitters. We show that vacuum fluctuations map small displacements of a nanomechanical oscillator onto large shifts in the transition frequency of a proximal emitter. This optically detectable shift consequently provides a mechanism for ultra-precise position measurements. This new technique works for a wide class of materials, as opposed to conventional methods based on optical forces. Optical forces are typically weak and cannot be applied to important materials such as graphene. Graphene is an excellent resonator with very low mass and high quality factor, which raises intriguing technological possibilities such as mass detection at the single-atom level. Current read-out techniques require averaging over many cycles of the mechanical motion. In contrast, our Casimir-based sensing scheme enables the monitoring of graphene motion at the quantum level in real time, which is not feasible using any other method. Our work constitutes the first example where Casimir potentials are utilized as a valuable resource for practical applications, which can already be realized with current technologies. This work merges the fields of graphene and quantum optics, and will open new avenues for strong-light matter interactions. [Preview Abstract] |
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K1.00067: Ultrahigh quality factor SiN membrane resonators for cavity optomechanics Srivatsan Chakram, Laura Chang, Airlia Shaffer, Yogesh Patil, Mukund Vengalattore We study the optomechanical properties of SiN membrane resonators through spectroscopic and interferometric imaging techniques. We demonstrate ultra-high quality factors of $50\times10^{6}$ and $f \times Q$ products of $1\times10^{14}$ Hz. These values correspond to the largest yet reported for mesoscopic flexural resonators [1]. We describe a mathematical model of radiation loss that accurately predicts our measured quality factors. Building upon this identification of clamping losses as the dominant dissipation mechanism, we also demonstrate enhancement of the mechanical quality factors by engineering a phononic band gap in the substrate. Our work paves the way towards the realization of quantum limited mechanical systems at room temperature. This work is supported by the DARPA QuASAR program through a grant from the ARO.\\[4pt] [1] S. Chakram et al., arXiv:1311.1234v1 [Preview Abstract] |
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K1.00068: Non-linear mode coupling for quantum optomechanics Srivatsan Chakram, Airlia Shaffer, Laura Chang, Yogesh Patil, Mukund Vengalattore We describe studies of resonantly enhanced parametric nonlinearities in an ultrahigh quality factor membrane resonator. The nonlinear coupling between two near-degenerate mechanical modes is induced by driving a third resonator mode. By varying the strength of the coupling, we demonstrate the continuous progression of the coupled system from linear ``two-mode'' dynamics to a highly nonlinear ``three-mode'' dynamics. The latter is characterized by a threshold behavior and mechanical bistability. This nonlinear coupling can be used for the amplification of weak phonon fields, signal transduction and thermomechanical squeezing. We also describe our progress on extending these studies to graphene nanoresonators. This work is motivated by the large quantum-limited nonlinearities inherent to graphene nanoresonators as well as the strong atom-resonator coupling due to the commensurate mass ratio. \\[4pt] This work is supported by the DARPA QuASAR program through a grant from the ARO. [Preview Abstract] |
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K1.00069: Hybrid Optomechanics in Strong Coupling Regime Yogesh Patil, Ajay Bhat, Harry Cheung, Sunil Bhave, Mukund Vengalattore We describe progress towards the realization of a hybrid optomechanical system consisting of an ultracold gas of atoms parametrically coupled to a microtoroidal optomechanical resonator. Our setup aims to harness the long-lived coherence of the collective atomic spin of an ultracold atomic gas to enhance the optomechanical coupling. This spin-mediated ultra-strong coupling aids in enhanced cooling of the mechanical resonator as well as in substantially increasing the sensitivity of micromechanical devices used in transduction applications, as also in inducing single-photon nonlinearities and other quantum processing [1]. We also report progress on using Raman sideband cooling and nondestructive imaging on fermionic species ($^{6}Li$), augmented by single site resolution imaging for effecting a quantum gas microscope.\\[4pt] [1] M. Aspelmeyer, T. J. Kippenberg, F. Marquardt, arXiv:1303.0733v1 (2013) [Preview Abstract] |
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K1.00070: Collision Microscope to Study Many-Body Quantum Entanglement Craig Price, Qi Liu, Nathan Gemelke Quantum entanglement over long length scales is present in both quantum critical and quantum ordered many-body systems and can often be used as a fingerprint for underlying dynamics or ground-state structure. Limited quantum measurement and thermal back-action via controlled collisions of cold atoms and subsequent optical detection can be used to probe long-range entanglement. Entanglement Entropy has recently arisen as a quantitative vehicle to describe entanglement in thermodynamic systems, and its scaling with area can reveal detailed character of the system. We present progress in constructing an apparatus to experimentally extract Entanglement Entropy through pair-wise entanglement of cold fermionic potassium and bosonic cesium gases. The measurement will be made by translating localized probe atoms through a portion of a strongly entangled sample, then recording the heating effect of back-action after optical detection of probe atoms. To do so, precise independent control over the atoms will be maintained in a bichromatic lattice\footnote{Rev Sci Inst 81,013109 (2010).} formed with a monolithic, common-mode optical setup imbedded in a quantum gas microscope. Other applications are discussed, including cooling of a Mott-Insulator and study of non-equilibrium quantum systems. [Preview Abstract] |
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K1.00071: Magnetometric Probe of an Ultra-cold Spinor Gas James Higbie Ultracold atoms have been shown to permit highly sensitive micron-scale magnetometric measurements. Here, we propose that a cold-atom magnetometer offers a new and sensitive method of probing the magnetic state of a second nearby ultracold spinor gas. We analyze the measurement back-action from such a magnetometric probe for polar-state and ferromagnetic-state probes, and compare to the Heisenberg limit. [Preview Abstract] |
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K1.00072: Hybrid Rydberg atom-photon-superconductor quantum interface J.D. Pritchard, J.A. Isaacs, M.A. Beck, R. McDermott, M. Saffman Hybrid quantum computation exploits the unique strengths of disparate quantum technologies, enabling realization of a scalable quantum device capable of both fast gates and long coherence times. We propose a quantum interface for creating hybrid entanglement between neutral atom and superconducting qubits. The interface is mediated by coupling superconducting qubits to microwave photons, and microwaves to Rydberg excited single atoms using chip-based coplanar waveguide microwave cavities. We have developed a simple gate scheme to enable entanglement of an atomic qubit with a microwave photon, with fidelity calculations based on realistic parameters giving Bell-state preparation fidelity exceeding 0.999 on $\mu$s timescales [1]. Experimental progress towards the coherent excitation of a single atom above a coplanar waveguide in a 4~K cryostat will be presented.\\[4pt] [1] J. D. Pritchard, J. A. Isaacs, M. A. Beck, R. McDermott and M. Saffman, \textit{Hybrid atom-photon quantum gate in a superconducting microwave resonator}, Phys. Rev. A \textbf{89}, 010301(R) (2014) [Preview Abstract] |
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K1.00073: Coupling cold atoms with mechanical oscillators Cris Montoya, Jose Valencia, Andrew Geraci, Matthew Eardley, John Kitching Macroscopic systems, coupled to quantum systems with well understood coherence properties, can enable the study of the boundary between quantum microscopic phenomena and macroscopic systems. Ultra-cold atoms can be probed and manipulated with micro-mechanical resonators that provide single-spin sensitivity and sub-micron spatial resolution, facilitating studies of decoherence and quantum control. In the future, hybrid quantum systems consisting of cold atoms interfaced with mechanical devices may have applications in quantum information science. We describe our experiment to couple laser-cooled Rb atoms to a magnetic cantilever tip. This cantilever is precisely defined on the surface of a chip with lithography and the atoms are trapped at micron-scale distances from this chip. To match cantilever mechanical resonances, atomic magnetic resonances are tuned with a magnetic field. [Preview Abstract] |
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K1.00074: Boson sampling with photon-added coherent states Jonathan Olson, Kaushik Seshadreesan, Keith Motes, Peter Rohde, Jonathan Dowling Boson sampling is a simple and experimentally viable model for non-universal linear optics quantum computing. Boson sampling has been shown to implement a classically hard algorithm when fed with single photons. This raises the question as to whether there are other quantum states of light that implement similarly computationally complex problems. We consider a class of continuous variable states---photon-added coherent states---and demonstrate their computational complexity when evolved using linear optical networks and measured using photodetection. We find that, provided the coherent state amplitudes are upper bounded by an inverse polynomial in the size of the system, the sampling problem remains computationally hard. [Preview Abstract] |
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K1.00075: Inhomogeneous broadening of optical transitions of $^{87}$Rb atoms in nanofiber-based optical lattices J. Lee, J.A. Grover, J.E. Hoffman, P. Solano, L.A. Orozco, S.L. Rolston We demonstrated nanofiber-based optical lattices [1] for $^{87}$Rb atoms using two-color evanescent trapping fields of 750nm and 1064nm lights which are not magic wavelengths for Rb. Rb atoms in our lattices experience strong light shifts (to the blue) on $\mathrm{5P_{3/2}}$ to all upper transitions, and the absorption profile is shifted to the blue. In addition, the ellipticity of a HE11 mode leads Zeeman broadening both on $\mathrm{5P_{3/2}}$ and $\mathrm{5S_{1/2}}$ due to vector light shifts. Here we present experimental results and a quantitative study of this inhomogeneous broadening based on light shifts, atomic temperature distribution, and population redistribution. The results can be used to estimate atom number and atom temperature with uncertainty of light polarization states, initial atom loading, and heating process in the experiment.\\[4pt] [1] E. Vetsch, et al., Phys. Rev. Lett. 104, 203603 (2010); A. Goban, et al., Phys. Rev. Lett. 109, 033603 (2012). [Preview Abstract] |
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K1.00076: QUANTUM COHERENT CONTROL |
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K1.00077: Quantum control using the Landau-Zener effect Tamas Budner, Jacob Hollingsworth, Michael Vennettilli, Ryan Zmiewski, Donald P. Fahey, Thomas J. Carroll, Michael W. Noel We excite ultracold rubidium atoms in a magneto-optical trap to a coherent superposition of two $|m_j|$ sublevels of a Rydberg state. After some delay, during which the relative phase of the superposition components can evolve, we apply a field ionization pulse (rise time $\sim$ 2~$\mu$s). The atoms traverse an avoided crossing in the Stark levels as they ionize. We find that we can control the final state distribution by varying the delay time and hence the relative phase. We present calculations which will be compared to the data. [Preview Abstract] |
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K1.00078: Understanding Zeeman EIT Noise Correlation Spectra in Buffered Rb Vapor Shannon O'Leary, Aojie Zheng, Michael Crescimanno Noise correlation spectroscopy on systems manifesting Electromagnetically Induced Transparency (EIT) holds promise as a simple, robust method for performing high-resolution spectroscopy used in applications such as EIT-based atomic magnetometry and clocks. During laser light's propagation through a resonant medium, interaction with the medium converts laser phase noise into intensity noise. While this noise conversion can diminish the precision of EIT applications, noise correlation techniques transform the noise into a useful spectroscopic tool that can improve the application's precision. Using a single diode laser with large phase noise, we examine laser intensity noise and noise correlations from Zeeman EIT in a buffered Rb vapor. Of particular interest is a narrow noise correlation feature, resonant with EIT, that has been shown in earlier work to be power-broadening resistant at low powers. We report here on our recent experimental work and complementary theoretical modeling on EIT noise spectra, including a study of power broadening of the narrow noise correlation feature. Understanding the nature of the noise correlation spectrum is essential for optimizing EIT-noise applications. [Preview Abstract] |
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K1.00079: Quantum synchronization of many coupled atoms for an ultranarrow linewidth laser Peiru He, Minghui Xu, David Tieri, Bihui Zhu, Ana Maria Rey, Kaden Hazzard, Murray Holland We theoretically investigate the effect of quantum synchronization on many coupled two-level atoms acting as high quality oscillators. We show that quantum synchronization -- the spontaneous alignment of the phase (of the two-level superposition) between different atoms -- provides a potential approach to produce robust atomic coherences and coherent light with ultranarrow linewidth and extreme phase stability. The atoms may be coupled either through their direct dipole-dipole interactions or, as in a superradiant laser, through an optical cavity. We develop a variety of analytic and computational approaches for this problem, including exact open quantum system methods for small systems, semiclassical theories, and approaches that make use of the permutation symmetry of identically coupled ensembles. We investigate the first and second order coherence properties of both the optical and atomic degrees of freedom. We study synchronization in both the steady-state, as well as during the dynamically applied pulse sequences of Rabi and Ramsey interferometry. This work was supported by the DARPA QuASAR program, the NSF, and NIST. [Preview Abstract] |
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K1.00080: Atomic coherences of on-resonant and off-resonant two-photon absorptions in ladder-type atomic system Han Seb Moon, Heung-Ryoul Noh We report the physical origins of the on-resonant and off-resonant two-photon absorption (TPA) in an open ladder-type atomic system of the 5S$_{1/2}$(F $=$ 1)-5P$_{3/2}$(F$^{\prime} =$ 0, 1, 2)-5D$_{5/2}$(F$'' = $ 1, 2, 3) transitions in $^{87}$Rb atoms. When the on-resonant TPA including electromagnetically induced transparency (EIT) was transformed into the off-resonant TPA according to the coupling laser frequency detuning, we clarified the dynamics of the atomic coherences by decomposing into the two-photon coherence (TC) and the crossover coherence (CC) terms mixed between one-photon coherence (OC) and TC terms The physical origins of the two TPAs were completely different; the cause of the on-resonant TPA was the CC term, and that of the off-resonant TPA was the TC term. [Preview Abstract] |
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K1.00081: A quantum network of clocks Peter Komar, Eric Kessler, Michael Bishof, Liang Jiang, Anders Sorensen, Jun Ye, Mikhail Lukin Shared timing information constitutes a key resource for positioning and navigation with a direct correspondence between timing accuracy and precision in applications such as the Global Positioning System (GPS). By combining precision metrology and quantum networks, we propose here a quantum, cooperative protocol for the operation of a network consisting of geographically remote optical atomic clocks. Using non-local entangled states, we demonstrate an optimal utilization of the global network resources, and show that such a network can be operated near the fundamental limit set by quantum theory yielding an ultra-precise clock signal. Furthermore, the internal structure of the network, combined with basic techniques from quantum communication, guarantees security both from internal and external threats. Realization of such a global quantum network of clocks may allow construction of a real-time single international time scale (world clock) with unprecedented stability and accuracy. See also: Komar et al. arXiv:1310.6045 (2013) and Kessler et al. arXiv:1310.6043 (2013) [Preview Abstract] |
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K1.00082: ABSTRACT WITHDRAWN |
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K1.00083: Quantum entanglement for doubly-excited resonance states of the helium atom Y.-C. Lin, T.K. Fang, Y.K. Ho It is well known that quantum entanglement is relevant to quantum information, quantum computation, quantum teleportation, and quantum cryptography. In our present work, quantum entanglement for doubly-excited resonance states are quantified by calculating the linear entropy ($S_{L})$ and von Neumann entropy ($S_{vN})$ for such states. The linear entropy is defined as $S_{L} =1-Tr\left( {\rho_{red}^{2} } \right)$ and the von Neumann entropy as $S_{vN} =-Tr\left( {\rho_{red} \log_{2} \rho_{red} } \right)$, where $\rho_{red} $ is the reduced density matrix, and \textit{Tr} denotes the trace of the matrix. In our previous works, we calculated the linear entropy for the bound states of the helium atom in free space [1]. Here, we employ the projection operator method [2] to calculate the energies and wave functions of doubly-excited resonance states in the helium atom. Using the projection operators $P$ and $Q$ with $P\left| \right\rangle =\left( {1-Q} \right)\left| \right\rangle $, we can evaluate the eigenvalues of $\left\langle {\mbox{\thinspace }} \right|QHQ\left| \right\rangle =\varepsilon_{res} \left\langle {\mbox{\thinspace }} \right|QQ\left| \right\rangle $, and such eigenvalues $\varepsilon_{res} $ approximate the resonance energies. Once the wave functions for the resonance states are obtained, we can use them to calculate the von Neumann and linear entropies of the doubly-excited resonance states. In the present work, we investigate the $^{\mathrm{1,3}}S^{\mathrm{e}}$, $^{\mathrm{1,3}}P^{\mathrm{o}}$, $^{\mathrm{1,3}}D^{\mathrm{e}}$, and $^{\mathrm{1,3}}F^{\mathrm{o}}$ resonance series in the helium atom lying below the He$^{\mathrm{+}}(N=$2) threshold. Our results indicate that different series will have different behaviors for their entropies. The detail of our findings will be presented at the meeting. [Preview Abstract] |
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K1.00084: Quantification of entanglement entropies in two-electron atomic systems by the Schmidt-Slater decomposition method Chien-Hao Lin, Yew Kam Ho We have carried out an investigation of the linear entropy and the von Neumann entropy for spatial (electron-electron orbital) entanglement for the two spin-1/2 fermions (electrons) in helium-like atomic systems. Hylleraas-type wave functions, in which the inter-electronic terms are included to take into account of correlation effects, are used to represent the ground and excited states of the two-electron wave functions with different nucleus charges. To quantify the entanglement entropies, we utilize the partial wave expansion procedure on the correlated Hylleraas functions, and employ the Schmidt-Slater decomposition method (see [1], and the references therein) to extract the eigenvalues for the one-particle reduced density matrix, from which the entropies can be determined. Our present results for linear entropy have shown good agreement with other available calculations using different methods [2, 3]. We will present our new results for the von Neumann entropy at the meeting.\\[4pt] [1] Ko\'{s}cik, P. \textit{Phys. Lett. A} \textbf{377}, 2393 (2013);\\[0pt] [2] Lin, Y.-C., Lin, C.-Y., and Ho, Y. K., \textit{Phys. Rev. A} \textbf{87}, 022316 (2013);\\[0pt] [3] Lin, C.-H., Lin, Y.-C. and Ho, Y. K., \textit{Few-Body Syst.} \textbf{54}, 2147 (2013). [Preview Abstract] |
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K1.00085: Optical control of coupled molecular states by ac Stark effect Jianbing Qi Quantum states with different spin multiplicity can be coupled through the interaction of the spin orbital motion of electrons. For example, the spin-orbit coupled rovibrational levels in diatomic alkali, which have different multiplicity in terms of total spin quantum number, and are classified as singlet states (if the total spin is zero) and triplet states (if the total spin is one), respectively. A transition from the singlet level can only go to singlet levels and a triplet only to triplet levels. Due to the spin-orbit coupling, however, the coupled states mix each other, therefore both states have singlet as well as triplet character. By coherently coupling the pair to an auxiliary quantum state, varying the Rabi frequency of the coupling laser and the detuning of the laser frequency, the coupling of the two mixed singlet-triplet molecular rovibrational levels can be modified by ac Stark effect. We use density matrix equations and a five-level molecular model to show that a coupled singlet-triplet pair of rovibrational levels can be used as a channel to optically control quantum states. [Preview Abstract] |
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K1.00086: Nanolayered microlenses in theory and practice Michael Crescimanno, James Andrews, Tom Oder, Chuanhong Zhou, Cory Merlo, Connor Hetzel, Cameron Bagheri, Joshua Petrus, Anthony Mazzocco Co-extruded layered polymer films with structurally designed optical dispersion are used as ``blanks'' from which micro lenses have been fabricated using grey-scale photo-lithography followed by plasma etching. We describe the materials and processing as well as techniques used to characterize the micro lenses and the physical optics theory used to model their measured behavior. [Preview Abstract] |
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K1.00087: Effect of Alignment on smectic A to nematic phase transition of the aligned octylcyanobiphenyl nano-liquid crystal Dipti Sharma Liquid Crystals (LCs) exhibit a wide range of mesomorphic phases for long range of applications either in the bulk form or as compounds and mixtures. In the smectic LC devices, more attention has been paying to get smectic phase transition earlier with higher quality reachers are showing their interest in the laser beam steering and the optical shutter applications to know how fast the smectic phase transition can be reached. Our interest is to understand the smectic A to nematic (SmA-N) phase transition behavior in the regard of its faster response. This study shows the effect of alignment on the activated kinetics of the SmA-N phase transition of the bulk octylcyanobiphenyl (8CB) under the effect of magnetic field. A detailed thermal analysis was performed for the aligned 8CB using high resolution calorimetry teachnique. A significant temperature shift in the transition peak was found towards higher temperature as ramp rate increases following Arrhenius behavior. This behavior gives the information of the energy dynamics of the molecular motion and rearrangement of 8CB molecules near the SmA-N transition. The presence of alignment brings faster response time, an increased energy dynamics with higher activation and would be helpful in the industrial area of liquid crystal devices. [Preview Abstract] |
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K1.00088: PHOTON INTERACTIONS WITH IONS, ATOMS AND MOLECULES |
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K1.00089: THE IRON PROJECT: High-Energy-Density (HED) Plasma Opacities and Diagnostics Yasin Gokce, T. Bostelmann, S. Nahar, A. Pradhan, J. Bailey The composition of the Sun, the benchmark for astronomical objects, has been a longstanding problem for the last few decades. The abundances of common elements in the Sun, such as, carbon, nitrogen, oxygen, supported by helioseismology are at discrepant by up to 50\% higher from those derived from state-of-the-art spectroscopy and elaborate 3-D radiative transfer models. The uncertainty is compounded by recent experiments at the Sandia National Laboratory on the Z-pinch inertial confinement fusion device which is able to re-create the HED plasma conditions existing at the solar radiative-convection zone boundary. Measured monochromatic iron opacities disagree with all known theoretical opacities models. The abundance problem and potential solution are related to radiative opacities. Uur continued investigation of the problem will be presented. We will also present collision strengths of carbon-like silicon which shows new resonances in the low energy region introduced by relativistic effects in the Breit-Pauli R-matrix method. Line intensity ratios of this ion, obtained for optically allowed transitions as seen in astronomical spectra, are the diagnostics for the density and termperature of the plasmas will be reported. [Preview Abstract] |
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K1.00090: Enhancement of X-ray dose absorption for medical applications Sara Lim, Sultana Nahar, Anil Pradhan, Rolf Barth, Robin Nakkula, Erica Bell Nanoparticles and compounds containing heavy element (high Z or HZ) could greatly increase the tumoricidal efficacy of X-radiation therapy via radiosensitization. This occurs because low energy X-rays can effectively ionize the inner shells of HZs, resulting in increased emission of damaging, high linear energy transfer (LET) electrons. To develop a comprehensive theoretical background to this process, numerical computations and Monte Carlo simulations using Geant4 for X-ray energy absorption and dose deposition in tissues were carried out at various energies. The enhancement in X-ray dose absorption due to HZ radiosensitization were determined. An absorption ratio, $\eta$, was developed to quantitatively compare radiosensitization by various broadband X-ray energies and HZ sensitizer concentrations. \emph{In vitro} experiments with the F98 rat glioma and B-16 mouse melanoma models were performed using platinum-based compounds to substantiate the computations and simulations. These results show that X-ray energies in the range below 100 keV are most efficient in achieving both the required penetrative depths and deposition of energy. Several issues regarding sensitizer concentration and chemotherapeutic efficacy as they relate to radiosensitization must be addressed [Preview Abstract] |
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K1.00091: Why criteria for impulse approximation in Compton scattering fail in relativistic regimes L.A. LaJohn, R.H. Pratt The assumption behind impulse approximation (IA) for Compton scattering is that the momentum transfer q is much greater than the average $ $ of the initial bound state momentum distribution p. Comparing with S-matrix results, we find that at relativistic incident photon energies ($\omega_i$) and for high Z elements, one requires information beyond $ /q$ to predict the accuracy of relativistic IA (RIA) diferential cross sections. The IA expression is proportional to the product of a kinematic factor $X^{nr}$ and the symmetrical Compton profile J, where $X^{nr}=1+cos^2\theta$ ($\theta $ is the photon scattering angle). In the RIA case, $X^{nr}$, independent of p, is replaced by $X^{rel}(\omega ,\theta ,p)$ in the integrand which determines J. At nr energies there is virtually no RIA error in the position of the Compton peak maximum ($\omega_f^{pk}$) in the scattered photon energy ($\omega_f$), while RIA error in the peak magnitude can be characterized by $ /q$. This is because at low $\omega_i$, the kinematic effects described by S-matrix (also RIA) expressions behave like $X^{nr}$, while in relativistic regimes (high $\omega_i$ and Z), kinematic factors treated accurately by S-matrix but not RIA expressions become significant and do not factor out. [Preview Abstract] |
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K1.00092: Double Photoionization of helium atom using Screening Potential Approach Haripada Saha The triple differential cross section for double Photoionization of helium atom will be investigated using our recently extended MCHF method [1]. It is well known that electron correlation effects in both the initial and the final states are very important. To incorporate these effects we will use the multi-configuration Hartree-Fock method to account for electron correlation in the initial state. The electron correlation in the final state will be taken into account using the angle-dependent screening potential approximation [2,3]. The triple differential cross section (TDCS) will be calculated for 20 eV photon energy, which has experimental results. Our results will be compared with available experimental [4] and the theoretical observations [5].\\[4pt] [1] H.P. Saha, (unpublished).\\[0pt] [2] M.R.H. Rudge, Rev. Mod. Phys. 40, 564 (1968).\\[0pt] [3] C.Pan and A.F Starace, Phys. Rev. Lett. 67, 185 (1991); Phys. Rev. A45, 4588 (1992).\\[0pt] [4] Brouning et al., J. Phys. B 31, 5149 (1998).\\[0pt] [5] Colgan et al., J.Phys. B 34, L457 (2001). [Preview Abstract] |
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K1.00093: Probing confinement resonances by photoionizing Xe inside a C$_{60}^+$ molecular cage R.A. Phaneuf, A.L.D. Kilcoyne, N.B. Aryal, K.K. Baral, C.M. Thomas, D.A. Esteves-Macaluso, R. Lomsadze, T.W. Gorczyca, C.P. Ballance, S.T. Manson, M.F. Hasoglu, J. Hellhund, S. Schippers, A. M\"{u}ller Double photoionization accompanied by loss of $n$ C atoms ($n = 0, 2, 4, 6$) was investigated by merging beams of Xe@C$_{60}^+$ ions and synchrotron radiation and measuring the yields of product ions. The giant $4d$ dipole resonance of the caged Xe atom has a prominent signature in the cross section for these product channels, which together account for $6.2 \pm 1.4$ of the total Xe $4d$ oscillator strength of 10. Compared to that for a free Xe atom, the oscillator strength is redistributed in photon energy due to multipath interference of outgoing Xe $4d$ photoelectron waves that may be transmitted or reflected by the spherical C$_{60}^+$ molecular cage, yielding so-called confinement resonances. The data are compared with an earlier measurement and with theoretical predictions for this single-molecule photoelectron interferometer system. Relativistic R-matrix calculations for the Xe atom in a spherical potential shell representing the fullerene cage show the sensitivity of the interference pattern to the molecular geometry. [Preview Abstract] |
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K1.00094: Molecular Calculations of the Photoionization of Endohedral Atoms: Ar@C$_{60}$ A. Ponzi, M. Stener, P. Decleva, S.T. Manson Endohedral fullerenes represent a particularly clean case of quantum confinement where the electronic properties of the guest atom or molecule are strongly modified by the encapsulating host.. Many theoretical studies, e.g [1-5], have been performed both on free C$_{60}$ and endohedral systems, and the predicted confinement resonances have been confirmed by recent experiment [6]. Most calculations have employed jellium models for the C$_{60}$ moiety, allowing the treatment of electron response effects and interchannel coupling [4,5], while the few molecular calculations have been limited to a static description, either at the DFT [1,2] or static-exchange level [5], giving, however, some conflicting evidence with interpretations based on jellium treatments. The development of large scale TDDFT codes [7] allows full treatment of nonspherical and response effects, and this methods is applied to Ar@C$_{60}$, to compare with results and assess the modifications brought about by the full inclusion of the ionic cores. It is found that molecular effects increase hybridization of the atomic orbitals with the cage and reduces the role of response effects, due to the stronger localization of the electron cloud. [1] P. Decleva \textit{et al}, \textit{J. Phys. B} \textbf{32}, 4523 (1999); [2] P. Colavita \textit{et al}, \textit{Phys. Chem. Chem. Phys}. \textbf{3}, 4481 (2001); [3] M. E. Madjet \textit{et al}, \textit{Phys. Rev. Lett}. \textbf{99}, 243003 (2007); [4] T. W. Gorczyca \textit{et al}, Phys. Rev. A \textbf{86}, 033204 (2012); [5] J. Jose and R. R. Lucchese, \textit{J. Phys. B} \textbf{46}, 215103 (2013); [6] R. A Phaneuf \textit{et al}, Phys. Rev A, \textbf{88}, 053402 (2013); [7] M. Stener \textit{et al, J. Chem. Phys}. \textbf{122}, 234301 (2005). [Preview Abstract] |
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K1.00095: Relativistic Effects in the Photoionization of High-Z Confined Atoms: Rn@C$_{60}$ David A. Keating, Steven T. Manson, Pranawa C. Deshmukh At high enough Z relativistic effects become important contributors to even the qualitative nature of atomic properties. This is likely to be true for confined atoms as well. To explore extent of relativistic effects in the photoionization of a heavy confined atom, a theoretical study of inner shells of radon (Z$=$86) confined in a C$_{60}$ cage has been performed using the relativistic random phase approximation (RRPA) methodology [1]. The effects of the C$_{60}$ potential modeled by a static spherical well which is reasonable in the energy region well above the C$_{60}$ plasmons [2]. In order to determine which features in the photoionization cross section are due to relativistic effects, calculations using the (nonrelativistic) random phase approximation with exchange method (RPAE) [3] are performed for comparison. It is found that relativistic interactions shift and split the nonrelativistic thresholds very considerably, and these changes in thresholds translate into very significant alterations to the nonrelativistic cross section; the large splitting of the 5d thresholds particularly affects the interchannel coupling of 5d with the other channels dramatically.\\[4pt] [1] W. R. Johnson and C. D. Lin, \textit{Phys. Rev. A} \textbf{20}, 964 (1979);\\[0pt] [2] V. K. Dolmatov, Adv. Quantum. Chem. \textbf{58}, 13 (2009);\\[0pt] [3] M. Ya. Amusia, \textit{Atomic Photoeffect} (Plenum, NY, 1990). [Preview Abstract] |
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K1.00096: Inner-Shell 2p Photoionization of Free and Confined Mg: Evolution of the Resonances with Depth of the Confining Potential Prabha Padukka, Hsiao-Ling Zhou, Steven T. Manson Relativistic Breit-Pauli R-Matrix calculations [1] of the photoionization cross sections of the inner 2p shell of free Mg and Mg confined in a C$_{60}$ molecule have been performed. The C$_{60}$ confinement potential is modeled as an attractive spherical potential of inner radius 5.8 a.u., thickness of 1.89 a.u. and a depth U$_{0}$ of 0.302 a.u. Multi-configuration wave functions for the final states of the ion core (target states) were obtained using modified MCHF and HF codes [2]. The calculations were performed for a variety of well depths up to 0.302 a.u in order to study the evolution of the photoionization cross section from free Mg to Mg@C$_{60}$. Particular attention was paid to the autoionizing resonances arising from the excitation 2p$_{1/2}$ and 2p$_{3/2}$; the lowest five series are given as 2p$^{5}(^{2}$P$_{3/2})$ns[3/2], 2p$^{5}(^{2}$P$_{1/2})$ns[1/2], 2p$^{5}(^{2}$P$_{3/2})$nd[3/2], 2p$^{5}(^{2}$P$_{3/2})$nd[1/2], 2p$^{5}(^{2}$P$_{1/2})$nd[3/2]. The resonances were identified and characterized using the eigenphase derivative technique, the QB method [3], and quantum defect theory. A complex pattern of changes occur with increasing well depth, with some of the resonances moving to lower photon energy and some to higher. This behavior is explained in terms of how the discrete orbitals are altered by the increasing depth of the well. [1] K. A. Berrington,W. B. Eissner, and P. H. Norrington, Comput.Phys. Commun. \textbf{92}, 290 (1995); [2] C. Froese Fischer, Comput. Phys. Commun. \textbf{64}, 431 (1991); [3] L. Quigley and K. Berrington, J. Phys. B \textbf{29}, 4529 (1996). [Preview Abstract] |
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K1.00097: Photoionization of Au$^{+}$ ions and developments in the synthesis of the metallofullerene Au@C$_{60}$ Kyren Bogolub, Alfred M\"uller, Stefan Schippers, Jonas Hellhund, Alexander Borovik, A.L. David Kilcoyne, Alex Aguilar, Allison Mueller, Andrea Johnson, David Macaluso Single photoionization of Au$^{+}$ ions was investigated via the merged-beams technique at AMO Beamline 10.0.1 of the Advanced Light Source at Lawrence Berkeley National Laboratory. The relative single photoionization yield was measured as a function of photon energy in the 45 eV to 120 eV energy range. These measurements were made in preparation for future photoionization studies of the endohedral metallofullerene Au@C$_{60}$, the production of which was also investigated. In proof--of--principle measurements a mass-resolved beam of Au@C$_{60}^{+}$ was produced with a primary ion beam current in the single picoamp range without optimization of the ion source or synthesis parameters. Plans are presented for improved metallofullere production yield to be used in photoionization measurements of the endohedral fullerene ions in conjunction with the continuing study of pure Au. [Preview Abstract] |
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K1.00098: Tracing ultrafast molecular transitions in C$_{2}$H$_{4}$ using twoÂcolor XUV pump XUV probe D. Ray, F.P. Sturm, T.W. Wright, N. Shivaram, I. Bocharova, A. Belkacem, Th. Weber We present the study of the ultrafast energy transfer near a conical intersection in C$_{2}$H$_{4}$, using an extreme ultraviolet (XUV) pump XUV probe scheme. The high harmonic pulses, which have sufficiently high flux to split into both pump and probe arms, are generated in a noble gas by IR pulses from our state of the art 30 mJ, 50 Hz laser system. The pulses are overlapped with the supersonic jet in our Momentum Imaging for TimE Resolved Studies (MISTERS) setup. The C$_{2}$H$_{4}$ is pumped by the 13.5 eV XUV pulses (9$^{\mathrm{th}}$ harmonic) to populate the excited valence state ($\pi $*)$^{2}$ orbitals. The double ionization of these molecular cations from this transient state is triggered by the 15$^{\mathrm{th}}$ harmonic (22.5 eV) as the probe. The ionic fragments are imaged with the reaction microscope. The MISTERS setup allows us to do an ion-ion coincidence detection in full 3D momentum space. The Kinetic Energy Release (KER) distributions are studied as a function of pump probe delay to trace the evolution of the transient states. [Preview Abstract] |
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K1.00099: Observing molecular dynamics with time-resolved 3D momentum imaging F.P. Sturm, T. Wright, I. Bocharova, D. Ray, N. Shivaram, J. Cryan, A. Belkacem, T. Weber, R. D\"orner Photo-excitation and ionization trigger rich dynamics in molecular systems which play a key role in many important processes in nature such as vision, photosynthesis or photoprotection. Observing those reactions in real-time without significantly disturbing the molecules by a strong electric field has been a great challenge. Recent experiments using Time-of-Flight and Velocity Map Imaging techniques have revealed important information on the dynamics of small molecular systems upon photo-excitation. We have developed an apparatus for time-resolved momentum imaging of electrons and ions in all three spatial dimensions that employs two-color femtosecond laser pulses in the vacuum and extreme ultraviolet (VUV, XUV) for probing molecular dynamics. Our COLTRIMS style reaction microscope can measure electrons and ions in coincidence and reconstruct the momenta of the reaction fragments in 3D. We use a high power 800 nm laser in a loose focusing geometry gas cell to efficinetly drive High Harmonic Generation. The resulting photon flux is sufficient to perform 2-photon pump-probe experiments using VUV and XUV pulses for both pump and probe. With this setup we investigate non-Born-Oppenheimer dynamics in small molecules such as C$_{2}$H$_{4}$ and CO$_{2}$ on a femtosecond time scale. [Preview Abstract] |
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K1.00100: Ultrafast Molecular Dynamics probed by Vacuum Ultraviolet Pulses James Cryan, Elio Champenois, Niranjan Shivaram, Travis Wright, Chan-Shan Yang, Roger Falcone, Ali Belkacem We present time-resolved measurements of the relaxation dynamics in small molecular systems (CO$_2$ and C$_2$H$_4$) following ultraviolet~(UV) photo-excitation. We probe these excitations through photoionization and velocity map imaging~(VMI) spectroscopy. Vacuum and extreme ultraviolet (VUV/XUV) pump and probe pulses are created by exploiting strong-field high harmonic generation~(HHG) from our state-of-the-art 30~mJ, 1~kHz laser system. Three dimensional photoelectron and photoion momentum images recorded with our VMI spectrometer reveal non-Born Oppenheimer dynamics in the vicinity of a conical intersection, and allow us track the state of the system as a function of time. We also present initial experiments with the goal of controlling the dynamics near a conical intersection using a strong-field IR pulse. Finally, we will show progress towards measurements of time-resolved molecular frame photoelectron angular distributions~(TRMFPADs) by applying our VUV/XUV pulse sequence to an aligned molecular ensemble. [Preview Abstract] |
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K1.00101: Photoionization of Au$^{+}$ ions and developments in the synthesis of the metallofullerene Au@C$_{60}$ Kyren Bogolub, David Macaluso, Allison Mueller, Andrea Johnson, Alfred M\"uller, Stefan Schippers, Jonas Hellhund, Alexander Borovik, Andre Anders, Alex Aguilar, A.L. David Kilcoyne Single photoionization of Au$^{+}$ ions was investigated via the~merged-beams technique at AMO Beamline 10.0.1.2 of the Advanced Light Source at Lawrence Berkeley National Laboratory. The relative single photoionization yield was measured as a function of photon energy in the 45 eV to 120 eV energy range. These measurements were made in preparation for future photoionization studies of the endohedral metallofullerene Au@C$_{60}$, the production of which was also investigated. In proof--of--principle measurements a mass-resolved beam of Au@C$_{60}^{+}$ was produced with a primary ion beam current in the single picoamp range without optimization of the ion source or synthesis parameters. Plans are presented for improved metallofullere production yield to be used in photoionization measurements of the endohedral fullerene ions in conjunction with the continuing study of pure Au. [Preview Abstract] |
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K1.00102: Probing Ultrafast Dynamics of Molecular Systems Using Inner Shell Transient Absorption Spectroscopy Adam Chatterley, Daniel Neumark, Stephen Leone, Oliver Gessner Femtosecond transient absorption spectroscopy employing extreme ultraviolet (XUV) light pulses can track molecular dynamics by monitoring the evolution of core to valence electronic transitions. Following ultrafast excitation of the system, these transitions offer real-time atomic site specific insight into the transient electronic structure of molecules including the transformation of bonds and the emergence of neutral and ionic fragments. An XUV transient absorption setup is presented that employs femtosecond high harmonic generation to produce photons beyond the sulfur 2p edge with energies up to 180 eV The technique will be used to explore photo-initiated nonadiabatic dynamics such as photodissociation and ring opening in isolated organosulfur compounds. Preliminary results will be presented on the dynamics of photodissociation in sulfur containing molecules, measured from the perspective of the sulfur atoms. [Preview Abstract] |
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K1.00103: Core-Hole Molecular Frame X-Ray Photoelectron Angular Distributions as Molecular Geometry Probes Cynthia Trevisan, Joshua Williams, Adrian Menssen, Thorsten Weber, Thomas Rescigno, Clyde McCurdy, Allen Landers We present experimental and theoretical results for the angular dependence of electrons ejected from the core orbitals of ethane (C$_{2}$H$_{6}$) and tetrafluoromethane (CF$_{4}$) in an effort to understand the origin of the imaging effect by which the molecular frame photoelectron angular distributions (MFPADs) for removing an electron from a 1s orbital effectively image the geometry of a class of molecules. At low energies, our calculations predict the same imaging effect in C$_{2}$H$_{6}$ previously found in CH$_{4}$, H$_{2}$O and NH$_{3}$. By contrast, in experiment and calculations CF$_{4}$ displays an anti-imaging effect, whereby the electron ejected by core photoionization has the tendency to avoid molecular bonds, if averaged over directions of polarization of the incident X-ray beam. Our measurements employ the COLTRIMS method and the calculations were performed with the Complex Kohn Variational method. [Preview Abstract] |
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K1.00104: Carbon K-shell molecular frame photoelectron angular distribution of neutral acetylene and the result of effective substitution of hydrogen by fluorine Samantha Fonseca, Ann Orel, Thomas Rescigno Detection of a diffracted photoelectron in the molecular fixed body frame is a promising chemical reaction imaging technique. We use the complex Kohn variational method to calculate molecular frame photoelectron distributions (MFPADs) for carbon 1s core ionization of neutral acetylene. We then substitute hydrogen for fluorine, breaking the~\textit{gerade, ungerade} symmetry and compare these MFPADs to the acetylene results. In addition, we consider the results of ionizing the fluorine 1s instead of the carbon. [Preview Abstract] |
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K1.00105: Interchannel coupling effects in the valence photoionization of SF$_{6}$ Jobin Jose, Robert Lucchese, Tom Rescigno The complex Kohn and polyatomic Schwinger variational techniques have been employed to illustrate the interchannel coupling correlation effects in the valence photoionization dynamics of SF$_{6}$. Partial photoionization cross sections and asymmetry parameters of six valence subshells (1$t_{1g}$, 5$t_{1u}$, 1$t_{2u}$, 3$e_{g}$, 1$t_{2g}$, 4$t_{1u})$ are discussed in the framework of several theoretical and experimental studies. The complex Kohn results are in rather good agreement with experimental results, indicative of the fact that the interchannel coupling effects alter the photoionization dynamics significantly. We find that the dominant effect of interchannel coupling is to reduce the magnitude of shape resonant cross sections near threshold and to induce resonant features in other channels to which resonances are coupled. [Preview Abstract] |
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K1.00106: Complementary Imaging of the Nuclear Dynamics in Laser-Excited Diatomic Molecular Ions in the Time and Frequency Domains Alex Kramer, M. Magrakvelidze, K. Bartschat, U. Thumm We investigated the bound and dissociative nuclear motion of vibrationally excited diatomic molecular by numerically calculating fragment-kinetic-energy-release spectra in the time and frequency domains. While the time-domain analysis shows nuclear oscillation periods, revival times, and the nuclear-probability-density evolution, quantum-beat (QB) imaging of the bound nuclear motion in the frequency domain complements time-domain investigations of the nuclear dynamics by revealing (i) QB frequencies and the nodal structure of vibrational states within a given adiabatic molecular potential curve and (ii) laser-electric-field-dressed molecular potential curves [1]. Our study of the variances and uncertainty products indicates increasing classical characteristics of the nuclear wave packet motion and fine-structure effects for increasingly massive dimers [2]. \\[4pt] [1] M. Magrakvelidze, A. Kramer, K. Bartschat, and U. Thumm, Submitted to J.Phys. B (2014). \\[0pt] [2] M. Magrakvelidze and U. Thumm, Phys. Rev. A 88, 013413 (2013). [Preview Abstract] |
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K1.00107: Towards jitter-free time resolved measurements at Xray Free Electron Lasers Gilles Doumy, Chris Roedig, Kai-Kai Zhang, Pierre Agostini, Lou DiMauro, Adrian Cavalieri, Ivanka Grguras, Michael Meyer, John Costello, Wolfram Helml, Reinhard Kienberger, Christoph Bostedt, Sebastian Schorb, Ryan Coffee The advent of X-ray Free Electron Lasers (XFEL) has quickly revolutionized the field of time resolved x-ray techniques. The availability of tunable pulses ranging from the soft to the hard x-ray region, and lasting only few tens of femtoseconds is enabling access to unprecedented temporal resolution using classic pump-probe techniques. Temporal resolution limits arise in large part from the timing jitter that exists inevitably between two independent sources. A significant effort to measure the timing jitter for every shot, tag the shots depending on the relative delay, and perform post sorting analysis of the data has yielded a precision around 25 fs (FWHM), a considerable improvement over the uncorrected jitter(400-500 fs (FWHM)). Importing the laser streaking techniques developed by the attophysics community, one can hope to use photoelectrons produced during the ultrashort x-ray pulse to define a reference to an external optical field, allowing extraction of the dynamics of a process of interest triggered by the x-ray pulse, using streaking by the same field. [Preview Abstract] |
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K1.00108: Mapping the fragmentation of acetylene with femtosecond resolution pump probe at LCLS using multi-particle coincidences Chelsea E. Liekhus-Schmaltz, Ian Tenney, Timur Osipov, Philip H. Bucksbaum, Vladimir S. Petrovic A newly commissioned three-layer delay line anode detector has been used in combination with x-ray pump x-ray probe time-resolved measurement at LCLS. We used $\sim$10 fs long x-ray pulses to probe by coulomb explosion the x-ray initiated ultrafast dynamics in the dication of acetylene (C$_2$H$_2^{+2}$), the smallest hydrocarbon that can isomerize. The dynamics are discerned from the temporal evolution of multi-particle coincidences which we identify by momentum conservation. We compare the results to those of deuterated-acetylene, which should have slower dynamics. [Preview Abstract] |
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K1.00109: Vacancy cascades in small molecules following x-ray inner shell photoionization D. Ray, R.W. Dunford, S.H. Southworth, E.P. Kanter, G. Doumy, Y. Gao, P.J. Ho, A. Picon We are investigating molecular effects in vacancy cascades of small molecules containing heavy atoms - IBr, Br$_{2}$ and CH$_{2}$BrI - following K-shell ionization. In addition to fundamental interest in the physics of such decay processes, there are practical applications such as medical treatments that use energetic fragmentation of iodinated compounds with high energy x-rays to selectively treat tumorous cells. Other biological applications are also promising. We utilize the tunable monochromatic x-ray beam at the Advanced Photon Source to trigger K-shell photoionization of Br and I, and measure charge distributions and the kinetic energies released to the fragment ions. A newly designed detection device allows us to do multi-fold coincidence measurements involving momentum imaging of all the ion fragments with very high detection efficiency in coincidence with x-ray fluorescence detection. By comparing the molecular fragmentation probabilities and the kinetic energies released in Br$_{2}$, IBr and CH$_{2}$BrI we aim to gain understanding of the fragmentation mechanism as a function of the bond distance between I and Br. [Preview Abstract] |
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K1.00110: X-ray ionization and fragmentation of XeF$_2$ S.H. Southworth, R.W. Dunford, G. Doumy, E.P. Kanter, B. Kr\"assig, P.J. Ho, A.M. March, C.S. Lehmann, A. Pic\'on, L. Young, D. Ray, R. Wehlitz An inner-shell hole produced by x-ray absorption in a heavy atom decays in a multi-step process with emission of fluorescent photons and Auger electrons. If the heavy atom is in a molecular environment, the initial hole and the holes produced by the first decay steps remain localized, but eventually charge is redistributed to neighboring atoms and the system Coulomb explodes. Such processes are responsible for x-ray damage in molecules and materials. It is informative to study charge redistribution in XeF$_2$ molecules in comparison with core-hole decays in atomic Xe [1]. We have used hard x rays at Argonne's Advanced Photon Source to produce Xe 1s holes and a multi-hit x-ray/ion spectrometer to measure charge distributions and kinetic energies released to the fragment ions. At Wisconsin's Synchrotron Radiation Center, soft x rays were used to measure ion charge-state yields resulting from Xe 3d$_{5/2}$, Xe 3d$_{3/2}$, and F 1s holes. To explore core-hole decay dynamics on the femtosecond time scale, x-ray-pump/x-ray-probe experiments are planned at the Linac Coherent Light Source. \\[4pt] [1] R. W. Dunford \textit{et al.} Phys. Rev. A {\bf 86}, 033401 (2012). [Preview Abstract] |
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K1.00111: Coupled-cluster methods for core-hole dynamics Antonio Picon, Lan Cheng, Jeff R. Hammond, John F. Stanton, Stephen H. Southworth Coupled cluster (CC) is a powerful numerical method used in quantum chemistry in order to take into account electron correlation with high accuracy and size consistency. In the CC framework, excited, ionized, and electron-attached states can be described by the equation of motion (EOM) CC technique. However, bringing CC methods to describe molecular dynamics induced by x rays is challenging. X rays have the special feature of interacting with core-shell electrons that are close to the nucleus. Core-shell electrons can be ionized or excited to a valence shell, leaving a core-hole that will decay very fast (e.g. 2.4 fs for K-shell of Ne) by emitting photons (fluorescence process) or electrons (Auger process). Both processes are a clear manifestation of a many-body effect, involving electrons in the continuum in the case of Auger processes. We review our progress of developing EOM-CC methods for core-hole dynamics. Results of the calculations will be compared with measurements on core-hole decays in atomic Xe and molecular XeF$_2$. [Preview Abstract] |
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K1.00112: Atomistic Computational Model of Radiation Damage of Nano-sized Systems in Intense X-ray Pulses Phay Ho, Wei Jiang, Kar Chun Lau, Linda Young We present a combined Monte-Carlo/molecular- dynamics (MC/MD) computational model that is suitable for monitoring the physics of intense, femtosecond XFEL pulses interacting with complex systems of various sizes, from nanometers to micrometers, and matters of various compositions. In this model, the occurrences of x-ray absorption, ionization, relaxation and electron-impact processes are treated by a MC method, and the subsequent dynamics of the all the electrons, ions and atoms are tracked using an MD method. Our model extends the previous MC/MD model [1] and provides new capabilities to probe the impacts of transient states on radiation damage dynamics. Recently, we have added LAMMPS as the driver of MD dynamics. This is a critical addition as now our code can run on Mira, a new petascale supercomputer with 786K core processors at the Argonne Leadership Computing Facility. Also, it can treat micron-sized systems with trillions of particles and both homogeneous and heterogeneous composition. Using our model, we examine the ionization dynamics of Argon clusters in an XFEL pulse as a function of particle sizes and pulse parameters, and we compare our results with the experimental data [2].\\[4pt] [1] Z. Jurek\textit{ et al}., Eur. Phys. J. D \textbf{29}, 217 (2004).\\[0pt] [2] S. Schorb \textit{et al}. PRL \textbf{108}, 233401 (2012). [Preview Abstract] |
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K1.00113: Mechanism of Resonance-enhanced X-ray Multiple Ionization of Argon Atom in an XFEL Pulse Linda Young, Phay Ho We present a new Monte Carlo rate equation (MCRE) approach to examine the inner-shell ionization dynamics of atoms in an intense x-ray free-electron laser (XFEL) pulse.~ In addition to photoionization, Auger decay and fluorescence processes, we include bound-to-bound transitions in the rate equation calculations.~ This computational tool allows us to account for ``hidden resonances" [1] unveiled in high charge states of atom in XFEL pulse.~ Using our MCRE approach, we investigated the ionization dynamics of Argon atom exposed to an 480-eV XFEL pulse.~ At this photon energy, it is not energetically allowed to produce Ar ions with charge 10$+$ and higher via direct one-photon L-shell ionization.~ Rather, we found that the resonance-enhanced x-ray multiple ionization (REXMI) pathways [2] play a dominant role in producing these highly charged ions.~ Our calculated results agree with the measured Ar ion yield data [3].~ More importantly, we account for the pulse-duration dependence of experimental ion yield data and identify the responsible REXMI pathways where excitation of multiple electrons into outer valence and Rydberg orbitals are followed by autoionization. [1] E. Kanter \textit{et al}. Phys. Rev. Lett \textbf{107}, 233001 (2012). [2] B. Rudek \textit{et al}. Nat. Photonics \textbf{6}, 858 (2012). [3] S. Schorb \textit{et al}. Phys. Rev. Lett \textbf{108}, 233401 (2012). [Preview Abstract] |
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K1.00114: Photodissociation of Methyl Iodide at 193 NM Hong Xu, Stephen Pratt A new measurement of the photodissociation of CH$_{3}$I at 193 nm is reported in which we use a combination of vacuum ultraviolet photoionization and velocity map ion imaging. The iodine photofragments are probed by single-photon ionization at photon energies above and below the photoionization threshold of I($^{2}$P$_{3/2})$. The relative I($^{2}$P$_{3/2})$ and I*($^{2}$P$_{1/2})$ photoionization cross sections are determined at these wavelengths by using the known branching fractions for the photodissociation at 266 nm. Velocity map ion images indicate that the branching fraction for I($^{2}$P$_{3/2})$ atoms is non-zero, and yield a value of 0.07 $\pm$ 0.01. Interestingly, the translational energy distribution extracted from the image shows that the translational energy of the I($^{2}$P$_{3/2})$ fragments is significantly smaller than that of the I*($^{2}$P$_{1/2})$ atoms. This observation indicates the internal rotational/vibrational energy of the CH$_{3}$ co-fragment is very high in the I($^{2}$P$_{3/2})$ channel. The results can be interpreted in a manner consistent with the previous measurements, and provide a more complete picture of the dissociation dynamics of this prototypical molecule. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract No. DE-AC02-06CH11357. [Preview Abstract] |
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K1.00115: Double resonance spectroscopy of molecular hydrogen near the third dissociation threshold Alexander Chartrand, Elizabeth McCormack Understanding the structure and dynamics of highly excited, long range states of molecular hydrogen is important as it has the potential to inform theoretical models that attempt to accurately account for extremely high energy and extremely long range interactions. Double-resonance laser spectroscopy via the $E,F$, $v = 6$ state was used to probe such an energy region: the third dissociation threshold of molecular hydrogen. Resonantly enhanced multi-photon ionization spectra were recorded by detecting ion production as a function of energy using a time-of-flight mass spectrometer. Assignments have been made to the $D'$ state, the $B''\bar{B}$ state and the energy and line width results compared to ab initio calculations. However, many features in this region of the spectrum remain unassigned. To guide us in further assignments, we are using Multi-Channel Quantum Defect Theory (MQDT) to make assignments to molecular Rydberg states converging to various levels of the ion. In addition, states with ion-pair configuration at long range and high vibrational levels of other valence states are considered. [Preview Abstract] |
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K1.00116: Calculating the Non--Adiabatic Pathways in STIRAP Yuan Sun, Harold Metcalf The various origins of the non--adiabaticity of the Stimulated Raman Adiabatic Passage (STIRAP) process is a long-standing, well-studied, and interesting topic.\footnote{K. Bergmann et al., Rev. Mod. Phys. {\bf{70}} 1003 (1998)} We have analyzed the details of STIRAP's non-adiabatic passage with a perturbative method that shares some of its characteristics with Feynman's path integral approach. The key contribution to the atomic evolution is from the pulse envelopes, timing, and shapes, a time dependence that remains after the rotating frame transformation that is usually employed to produce a time-independent Hamiltonian. Our resulting propagator describes the time evolution of the quantum system, and the different perturbation orders allow for a better and more intuitive view of STIRAP's non-adiabatic behavior. The method can be extended to other problems where the higher orders of the actual paths matter during the time evolution. [Preview Abstract] |
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K1.00117: Angular Momentum Exchange in Atomic E2 Transitions Stefan Evans, Harold Metcalf Electric quadrupole (E2) transitions in atoms require $\Delta\ell=2\hbar$ but ordinary light carries angular momentum of only $1\hbar$. However, Laguerre Gaussian beams can carry arbitrary integer orbital angular momentum (OAM). Atomic E2 transition matrix elements are typically smaller than those of electric dipole transitions by a factor of $\alpha^2 \approx 10^{-5}$, but may be enhanced by angular momentum mixing in atomic states. Instead of seeking these, we look for a nearly pure E2 transition and this means a low-Z atom. While a plane wave approximation is valid for a Gaussian beam, this may not be the case for light with OAM, where the electric field profile is steep near the radial singularity. We compare this gradient to that of a plane wave and incorporate the electric field distribution and gradients into the E2 transition matrix elements. Also important is how large an area of the beam profile interacts with the atom and where to place the atomic sample in the beam profile. [Preview Abstract] |
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K1.00118: On the enhancement of the back-to-back two-electron-one photon ionization in molecules Miron Amusia, Eugene Drukarev Recently, the long ago predicted quasi-free mechanism of two-electron photoionization [1] was detected already at relatively low energy photoionization in He [2]. It was observed that some pairs of electrons are leaving the target atom back-to-back, i.e. in opposite direction with almost the same energy. They have opposite spin directions. The cross-section of this process depends upon the probability for a pair of electrons to be close to each other before meeting the incoming photon. Such probability is greatly enhanced in molecules with covalent bonding, like H$_{2}$. In this and similar molecules the electrons spend an essential part of time being between nuclei and thus screening them from each other. We demonstrate that indeed the back-to-back contribution is much bigger in H$_{2}$ than in He. We analyze qualitatively some other situations that lead to relative growth of back-to-back contribution. Atoms with electrons with bigger principal quantum numbers have bigger back-to-back contributions. An external pressure applied to molecules forces electrons to be closer to each other. As a result for them the back-to-back contribution can be controllable enhanced.\\[4pt] [1] M. Ya. Amusia et al, JPB, 1975, 8, 1248.\\[0pt] [2] M. S. Scheffler et al, M S PRL, 2013, 111, pp.013003 [Preview Abstract] |
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K1.00119: Polarization Sensitive Coherent Anti-Stokes Raman Spectroscopy of DCVJ in Doped Polymer Laszlo Ujj Coherent Raman Microscopy is an emerging technic and method to image biological samples such as living cells by recording vibrational fingerprints of molecules with high spatial resolution. The race is on to record the entire image during the shortest time possible in order to increase the time resolution of the recorded cellular events. The electronically enhanced polarization sensitive version of Coherent anti-Stokes Raman scattering is one of the method which can shorten the recording time and increase the sharpness of an image by enhancing the signal level of special molecular vibrational modes. In order to show the effectiveness of the method a model system, a highly fluorescence sample, DCVJ in a polymer matrix is investigated. Polarization sensitive resonance CARS spectra are recorded and analyzed. Vibrational signatures are extracted with model independent methods. Details of the measurements and data analysis will be presented. [Preview Abstract] |
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K1.00120: POSTDEADLINE |
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K1.00121: Theoretical Characterizaiton of Visual Signatures (Muzzle Flash) D.O. Kashinski, A.N. Scales, D.L. VanderLey, G.M. Chase, O.E. Di Nallo, E.F.C. Byrd We are investigating the accuracy of theoretical models used to predict the visible, ultraviolet and infrared spectra of product materials ejected from the muzzle of currently fielded systems. Recent advances in solid propellants has made the management of muzzle signature (flash) a principle issue in weapons development across the calibers. \emph{A priori} prediction of the electromagnetic spectra of formulations will allow researchers to tailor blends that yield desired signatures and determine spectrographic detection ranges. We are currently employing quantum chemistry methods at various levels of sophistication to optimize molecular geometries, compute vibrational frequencies, and determine the optical spectra of specific gas-phase molecules and radicals of interest. Electronic excitations are being computed using Time Dependent Density Functional Theory (TD-DFT). A comparison of computational results to experimental values found in the literature is used to assess the affect of basis set and functional choice on calculation accuracy. The current status of this work will be presented at the conference. [Preview Abstract] |
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K1.00122: Percent-level accuracy in measuring photoionisation yields and peak intensities for intense few-cycle laser pulses David Kielpinski, W.C. Wallace, O. Ghafur, J.E. Calvert, C. Khurmi, D.E. Laban, I.V. Litvinyuk, R.T. Sang, K. Bartschat, A.N. Grum-Grzhimailo, D. Wells, H.M. Quiney, X.M. Tong The correct interpretation of experimental results in strong-field physics depends critically on both the measurement precision and on accurate knowledge of the laser peak intensity. We have accurately measured the photoionization yields of atomic hydrogen (H) and molecular hydrogen ($\mbox{H}_2$) in intense, few-cycle laser pulses, and compared them against various theoretical models. From our comparison with highly precise numerical solutions of the three-dimensional (3D) time-dependent Schr{\"o}dinger equation (TDSE), we have derived an intensity calibration standard accurate to better than 3\%. This standard is easily usable in any strong-field physics experiment capable of measuring photoionization yields. [Preview Abstract] |
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K1.00123: Rydberg blockade in three-atom systems Daniel Barredo, Sylvain Ravets, Henning Labuhn, Lucas Beguin, Aline Vernier, Radu Chicireanu, Florence Nogrette, Thierry Lahaye, Antoine Browaeys The control of individual neutral atoms in arrays of optical tweezers is a promising avenue for quantum science and technology [1,2]. Here we demonstrate unprecedented control over a system of three Rydberg atoms arranged in linear and triangular configurations. The interaction between Rydberg atoms results in the observation of an almost perfect van der Waals blockade [3]. When the single-atom Rabi frequency for excitation to the Rydberg state is comparable to the interaction energy, we directly observe the anisotropy of the interaction between nD--states. Using the independently measured two-body interaction energy shifts we fully reproduce the dynamics of the three-atom system with a model based on a master equation without any adjustable parameter. Combined with our ability to trap single atoms in arbitrary patterns of 2D arrays of up to 100 traps separated by a few microns, these results are very promising for a scalable implementation of quantum simulation of frustrated quantum magnetism with Rydberg atoms. \\[4pt] [1] E.~Urban \emph{et at.}, \emph{Nat. Phys.} \textbf{5} 110 (2009).\\[0pt] [2] A.~Gaetan \emph{et at.}, \emph{Nat. Phys.} \textbf{5} 115 (2009).\\[0pt] [3] L.~Beguin, A.~Vernier, R.~Chicireanu, T.~Lahaye, and A.~Browaeys, \emph{Phys. Rev. Lett.} \textbf{110} 263201 (2013). [Preview Abstract] |
(Author Not Attending)
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K1.00124: Electron transfer mediated decay of outer-valence ionised states Kirill Gokhberg, Vasili Stumpf, Lorenz S. Cederbaum Electronically excited states of atoms and molecules embedded in an environment may efficiently decay by ionising neighbouring species in the energy or charge transfer mediated processes. The energy transfer driven interatomic Coulombic decay (ICD) has been shown to proceed on a fs time scale in weakly bonded systems upon the production of a localised electronic excitation. Related electron transfer mediated decay (ETMD) is usually a slower process and becomes an important relaxation pathway whenever ICD channel is unavailable. In this talk we show that this situation is realised for singly and multiply outer-valence ionised atoms in a medium leading to unexpected physical effects. In particular, we demonstrate that ETMD provides an efficient and general neutralisation pathway for multiply charged ions produced via Auger decay in an environment. As an example we show the results of an ab initio study of the NeKr$_2$ cluster following the Auger decay of 1s vacancy of Ne. We also discuss how the single photon double ionisation efficiency can be dramatically enhanced in a medium due to ETMD. As an example we show that the double ionization cross section of Mg in MgHe cluster becomes three orders of magnitude larger than the respective cross section of the isolated Mg atom. [Preview Abstract] |
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K1.00125: Nuclear quantum dynamics in warm dense hydrogen Jianmin Yuan, Dongdong Kang, Jiayu Dai, Huayang Sun Quantum dynamics is a challenging problem in atomic and molecular dynamics. Ionic and electronic transport behaviors are strongly dependent on their dynamics, whose key physics is the scattering or collisions between particles. We usually consider only the quantum effects of electrons, but neglect the quantum effects of ions. Here, we show that the nuclear quantum effects can induce quantum tunneling in warm dense hydrogen, resulting in larger ionic diffusions and less electronic transport such as electrical and thermal conductivities. In order to study the nuclear quantum dynamics, we modify the sampling formula in path integral molecular dynamics (centriod molecular dynamics, CMD). Using the new sampling, the tunneling probability from CMD is consistent with the results of WKB approximation and full quantum mechanical calculations near the classical limit. The significant quantum delocalization of ions introduces expressively different scattering cross section between protons compared with classical particle treatments, which can explain the large alterability of transport behaviors. The complex behavior shows that NQEs cannot be neglected for dense hydrogen even in the warm dense regime, which would be important for the giant planets and inertial confinement fusion. [Preview Abstract] |
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K1.00126: Dynamical core polarization in strong-field ionization Zengxiu Zhao, Bin Zhang, Jianmin Yuan Core polarization plays an important role in both ionization and high harmonic generation processes of molecules driven by strong laser fields. With our recently developed three-dimensional time-dependent Hartree-Fock method, we investigate the orientation-dependent ionization of CO molecules. It is found that the full ionization results are in good agreement with the recent experiment. The comparisons between the full method and the single-active-orbital method show that although the core electrons are generally more tightly bound and contribute little to the total ionization yields, their dynamics cannot be ignored, which effectively modifies the behavior of electrons in the HOMO. By incorporating it into the SAO method, we identify that the dynamic core polarization plays an important role in the tunneling ionization of CO molecules, which is helpful for the future development of the tunneling ionization theory beyond the single active electron approximation. In order to further verify the role of core polarization, exact calculations are performed for the ionization of two-electron model systems by strong laser fields. The limitations of HF and the SAE are quantified and the tunneling ionization rate is shown improved with the core-polarization induced correction. [Preview Abstract] |
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K1.00127: A complete dataset of copper for investigation of element abundance Jiaolong Zeng, Yanpeng Liu, Jianmin Yuan The abundance of copper plays an important role in the chemical evolution of various stars, such as giant stars and solar-type stars. Accurate determination of its abundance helps to clarify a number of problems including the quite different behavior from other Fe-peak elements both in our Galaxy and extragalactic systems and the [Cu/Fe] ratios in Galactic stars. To accurately determine the copper abundance, it is necessary to include the non-local thermodynamic equilibrium (NLTE) effects, which depend on a complete dataset of atomic data. However, the complexity of electronic structure of copper makes the accurate prediction of a complete set of atomic data difficult. For both atomic Cu and the first ionized Cu II, the energies of 3d and 4s orbitals are very close and their competition results in complex energy levels. The excitation energy of 3d orbital is very low resulting in an opening 3d atomic system which is difficult to deal with theoretically due to the strong electron correlations. We present a complete set of atomic data including the energy levels, oscillator strengths, and photoionization cross sections of Cu I for the NLTE modeling in copper abundance investigation of astrophysical objects. The calculations are performed with the R-matrix method. [Preview Abstract] |
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K1.00128: Two-color probe of high harmonic generation from argon atoms Zengxiu Zhao, Jianmin Yuan, Chao Meng, Wenbo Chen Two-color control of high harmonic generation has been proven a powerful in situ tool to characterize the intrinsic chirp of attosecond bursts. The weak second harmonic pulse introduces a phase modulation of the strong field quantum processes, leading to the generation of even-order harmonic. We measure the yields of even-order harmonics from argon gases as a function of the phase delay between the fundamental and its second harmonic pulse. We found that the modulation of even-order harmonics exhibits a phase jump around the 28th harmonic (48eV), closely resembling the result from. However, we show by varying laser intensity that the phase jump is unlikely to be attributed to the switching from short to long trajectories of HHG near the cut-off. In addition, we demonstrate that the phase of jump depends on the driving laser wavelength. Single-active-electron simulation fails to reproduce the experimental observation. We therefore suspect that multielectron response comes into play for the two-color control of HHG from Argon. Preliminary analysis suggests that there exists competing pathways of HHG from inner orbitals, even for argon atoms whose interaction with strong laser fields is usually assumed well described by SAE approximation. [Preview Abstract] |
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K1.00129: Electron impact multiple ionization cross sections of heavy ions Jiaolong Zeng, Pengfei Liu, Jiayu Dai, Jianmin Yuan Cross sections of electron impact ionization are important in modeling both astrophysical and laboratory plasmas. For heavy ions, accurate determination of this microscopic physical quantity is difficult due to the complex atomic structure. At high incident electron energy, inner-shell excitation and ionization processes can occur, which will result in complicated decay including Auger and radiative decay processes. For deep inner-shell excitation and ionization, cascaded Auger processes are very likely. Under conditions of collisional ionization equilibrium, the balance of electron-ion recombination and electron impact single ionization determines the charge state distribution (CSD). Accurate CSD, which in turn determined by accurate cross sections, is very important in a wide regime of spectroscopic diagnostics to infer the physical conditions of plasmas such as the electron temperature, electron density, and elemental abundance. As an illustrative example, the cross sections from the ground configuration of Sn$^{13+}$ in forming Sn$^{13+}$, -Sn$^{16+}$ are reported in detail. The contributions from the electron impact excitation, electron impact ionization and resonant excitation processes are included. [Preview Abstract] |
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K1.00130: Accurate temperature dependent interatomic potential for dense matter based on ab initio calculations Jiayu Dai, Huayang Sun, Jianmin Yuan Combining molecular dynamics, ab initio molecular dynamics is capable of simulating various dynamic behaviors relevant to temperatures, pressures and laser fields. However, because of the computational cost and limitation by parallel methods, AIMD is usually applied to systems containing a few hundreds of atoms, which condemns its application to the study of dynamic compression, phase transition, and transport behaviors. Although classical molecular dynamics can investigate large systems of more than 10$^{6}$ atoms, it requires accurate and wide range temperature-dependent interatomic potentials which are seldom available, in particular for the dense matter. Here, we construct new temperature-dependent interatomic potentials using neural network method, based on the structures and energies from AIMD using tens of atoms. The new potential is implemented in CMD and the computational efficiency is found improved by 10$^{3}$ times. Using the new potential, the calculated energies, pressures and melting points in a wide range of temperature and pressure are almost the same as that from the AIMD method. Based on this new approach, it is possible to investigate dynamic compression processes and phase transitions within the accuracy of ab initio method. [Preview Abstract] |
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K1.00131: Polarizabilities of Lanthanides and Actinides Alexander Kozlov, Vladimir Dzuba, Victor Flambaum Polarizability of single atoms has being a subject of investigation for a long period of time. It determines interaction of atom with light which is used in optical lattice trapping and optical lattice based atomic clocks, van der Waals forces between atoms and atom-walls interaction. Experimental measurements and theoretical calculations of polarizability for few-electron elements reach as high as one percent discrepancy. Although for more complicated many valence electron systems there's almost no experimental data nor theoretical predictions due to complexity of such a calculations. We focus on polarizability calculations for ground and few excited states of lanthanides and actinides. These elements are of the great experimental interest for ultraprecise atomic clocks, searches for variation of fundamental constants and parity non-conservation, application in study of quantum gasses. Calculations for atoms with opened f-shell are very complicated and usually have poor accuracy. There is no published data for most of actinides and lanthanides and the accuracy of unpublished results is not determined. We calculate scalar polarizabilities for ground and first few exited states as well as tensor polarizabilities of ground states of opened f-shell elements. [Preview Abstract] |
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K1.00132: Photoionization of PII Sultana Nahar, E. Hern\'andez, L. Hern\'andez, A. Antill\'on, A. Morales, O. Gonz\'alez, D. Macaluso, D. Hanstorp, A. Convington, K. Chartkunchand, A. Aguilar, A. Ju\'arez, G. Hinojosa The cross section and spectrum of single photoionization of phosphorus cation was measured in the energy range from threshold to 50 eV with a photon energy resolution of 40 meV. A close coupling R-matrix calculation is compared to the experimental data. The spectrum is composed of a non resonant cross section over which resonant structure consisting is several Rydberg series is superimposed. The spectrum shows evidence of electronic excitation in the initial PII ion and strong interaction between nonresonant cross section and resonant structure. Montana Space Grant Consortium, Swedish Research Council, CONACYT CB-2011 167631- [Preview Abstract] |
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K1.00133: Photoionization of ClII Sultana Nahar, E. Hern\'andez, A. Antill\'on, A. Morales, O. Gonz\'alez, D. Macaluso, D. Hanstorp, A. Aguilar, A. Ju\'arez, G. Hinojosa The cross section and spectrum for the process of single photoionization of the chlorine cation was measured in the energy range of 19.5 to 28.0 eV with a photon energy resolution of 20 meV. Over a non resonant cross section, resonant structures originated from initinal Cl+ 3P(J=0,1,2) manifold converging mainly to 2P(J=3/2) and 2D(J=5/2) are identified. A theoretical calculation based on the close coupling R-matrix is under progress. CONACYT CB-2011 167631 [Preview Abstract] |
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K1.00134: Intensity-modulated polarizabilities and magic trapping of alkali-metal and divalent atoms in infrared optical lattices Turker Topcu, Andrei Derevianko Long range interactions between neutral Rydberg atoms has emerged as a potential means for implementing quantum logical gates. These experiments utilize hyperfine manifold of ground state atoms to act as a qubit basis, while exploiting the Rydberg blockade mechanism to mediate conditional quantum logic. The necessity for overcoming several sources of decoherence makes magic wavelength trapping in optical lattices an indispensable tool for gate experiments. The common wisdom is that atoms in Rydberg states see trapping potentials that are essentially that of a free electron, and can only be trapped at laser intensity minima. We show that although the polarizability of a Rydberg state is always negative, the optical potential can be both attractive or repulsive at long wavelengths (up to $\sim$10$^4$ nm). This opens up the possibility of magic trapping Rydberg states with ground state atoms in optical lattices, thereby eliminating the necessity to turn off trapping fields during gate operations. Because the wavelengths are near the CO$_2$ laser band, the photon scattering and the ensuing motional heating is also reduced compared to conventional traps near low lying resonances, alleviating an important source of decoherence. [Preview Abstract] |
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K1.00135: Magnetic field control of the linear and nonlinear optical absorption in two-dimensional quantum nanorings Oleg Olendski Linear and nonlinear optical absorption coefficients of the two-dimensional quantum nanoring in the perpendicular magnetic field $\bf B$ are calculated within independent electron approximation. Characteristic feature of the energy spectrum are crossings of the levels with adjacent nonpositive magnetic quantum numbers $m$ as the intensity $B$ changes. It is shown that the absorption coefficient of the associated optical transition is drastically decreased at the fields corresponding to the crossing. Proposed model of the Volcano disc allows to get simple mathematical analytical results which allow clear physical interpretation. An interplay between positive linear and intensity-dependent negative cubic absorption coefficients is discussed; in particular, critical light intensity at which additional resonances appear in the total absorption dependence on the light frequency, is calculated as a function of the magnetic field and levels' broadening. [Preview Abstract] |
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K1.00136: Cold Atom Electron/Ion Source with Rydberg Blockade and Electromagnetically Induced Transparency Ben Sparkes, Dene Murphy, Richard Taylor, Rory Speirs, Dan Thompson, Robert Scholten Rydberg atoms provide an interesting system for research on long-range dipole interactions and applications including quantum information and quantum simulations. At the low temperatures and atomic densities typical of laser-cooled atom clouds, the dipole interaction can lead to Rydberg blockade, where an atom in a Rydberg state will affect the internal energy levels of neighbouring atoms, preventing simultaneous excitation. Rydberg blockade can create spatial order and thereby reduce disorder-induced heating which currently limits the minimum temperature of ultracold plasmas and cold atom electron and ion sources (CAEIS). We will present our latest results investigating Rydberg blockade and disorder-induced heating from our rubidium CAEIS. Combining the competing effects of Rydberg blockade with our ability to shape the electron and ion bunches can in principle allow improvements to the brightness and emittance of the source for nanofabrication and imaging. We have also used the bunch shaping ability to probe the transition from blockade to electromagnetically induced transparency (EIT). EIT can be used to determine the coherence of the atomic system, and the combination of EIT with Rydberg blockade has potential for use in photonic phase gates. [Preview Abstract] |
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K1.00137: Space-charge dynamics in ultra-cold ion bunches Robert Scholten, Dene Murphy, Rory Speirs, Daniel Thompson, Benjamin Sparkes, Andrew McCulloch Cold ion sources based on photoionisation of laser cooled atoms provide a unique system for investigating Coulomb interactions within complex charged particle bunches. Space-charge driven expansion in charged particle beams is of critical importance for applications including electron and ion microscopy, mass spectrometry, synchrotrons and x-ray free electron lasers, and in electron diffraction where space-charge effects constrain the capacity to obtain diffraction information. Self-field effects are often difficult to observe because of thermal diffusion with traditional sources. Cold atom sources produce ions with temperatures of a few mK, such that subtle space-charge effects are apparent. We illustrate the capabilities through detailed investigation of a complex ion bunch shape, showing collective behaviour including high density caustics and shockwave structures arising from long-range interactions between small charge bunches. [Preview Abstract] |
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K1.00138: Rotation Measurement with a K-Rb-$^{21}$Ne Atomic Spin Co-magnetometer Gyroscope Yao Chen, Sheng Zou, Lihong Duan, Jiancheng Fang Co-magnetometers based on K-$^{3}$He and K-Rb-$^{21}$Ne [1] have been used to test of CPT symmetry. For the K- Rb-$^{21}$Ne co-magnetometer, due to the gyroscopic effect of the $^{21}$Ne nuclear spin, it can also be used to sense small rotation. For inertial navigation application, $^{21}$Ne atoms, whose gyromagnetic ratio is an order of smaller than $^{3}$He, is better to be used to sense rotation. The spin projection noise of a K-Rb-$^{21}$Ne co-magnetometer with measurement volume of 1cm$^{3}$ could be on the order of 10$^{-10}$ rad/s/Hz$^{1/2}$. A K-Rb-$^{21}$Ne co-magnetometer gyroscope has been designed. It is under constructing in our laboratory and the rotation of the earth should be measured by this apparatus. We also have made alkali vapor cells filled with K and Rb atoms, whose mole fraction ratio is controlled by analytical balance operated in the anaerobic glove box. \\[4pt] [1] M. Smiciklas, J. M. Brown, L. W. Cheuk, S. J. Smullin, and M. V. Romalis, Phys. Rev. Lett. 107, 171604 (2011). [Preview Abstract] |
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K1.00139: The Second Generation ACME Electron EDM Experiment Jacob Baron, Wes Campbell, David DeMille, John Doyle, Gerald Gabrielse, Yuliya Gurevich, Paul Hess, Nicholas Hutzler, Emil Kirilov, Ivan Kozyryev, Brendon O'Leary, Cristian Panda, Maxwell Parsons, Elizabeth Petrik, Benjamin Spaun, Amar Vutha, Adam West We present a proposal to upgrade the ACME experiment to make a more precise measurement of the electron's electric dipole moment (eEDM). We plan a number of improvements to increase statistical sensitivity and suppress known systematic effects. Statistical sensitivity improvements include an upgraded molecular beam source, a molecular electrostatic guide, and a coherent state preparation scheme. We estimate a sensitivity improvement of at least an order of magnitude over our previous measurement [1]. \\[4pt] [1] The ACME Collaboration et al., \textit{Science} \textbf{343}, (2014) 269-272. [Preview Abstract] |
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K1.00140: Time delays for attosecond streaking in photo-ionization of neon Johannes Feist, Oleg Zatsarinny, Stefan Nagele, Renate Pazourek, Joachim Burgd\"orfer, Xiaoxu Guan, Klaus Bartschat, Barry Schneider Time-resolved photoemission in neon atoms as probed by attosecond streaking has been of much interest and debate. We compute streaking time shifts for the emission of 2p and 2s electrons and their relative delay and compare with recent experimental data by Schultze et al. [Science {\bf 328}, 1658 (2010)]. We employ the $B$-spline $R$-matrix method to calculate accurate Eisenbud-Wigner-Smith time delays from the multielectron dipole transition matrix elements for photoionization. The laser field-induced time shifts in the exit channel are obtained from separate, time-dependent simulations of a full streaking process by solving the time-dependent Schr\"odinger equation on the single-active-electron level. The resulting relative streaking time shifts between 2s and 2p emission lie well below the experimental data. We identify the presence of unresolved shake-up satellites in the experiment as a potential source of error in the determination of streaking time shifts. However, preliminary results indicate that shake-up states only increase the discrepancy between calculation and experiment. [Preview Abstract] |
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K1.00141: Two-photon double-ionization of the H$_2$ molecule in light perpindicular to the internuclear axis: effects of pulse duration Xiaoxu Guan, Klaus Bartschat, Barry Schneider, Lars Koesterke Earlier~[1--3], we solved the time-dependent Schr\"odinger equation to calculate the two-photon double ionization of the hydrogen molecule induced by non-sequential absorption of photons with a central energy of 30~eV in a short laser pulse lasting for about 1.6~femtoseconds. The linear polarization of the radiation was aligned with the internuclear axis. At the equilibrium distance R$_{eq}$, several doubly excited $^1\Sigma_{g,u}$ states, accessible through photon absorption,lie about 30~eV above the $X\,^1\Sigma_g$ ground state. These states are likely responsible for the significant disagreement seen in the literature for previous results on both angle-integrated and angle-differential cross sections. Here we continue to explore the fundamental role of doubly excited states on the two-photon break-up process,now for the even more difficult problem of laser polarization perpendicular to the internuclear axis. Such studies require relatively long laser pulses, thus making the calculations computationally very challenging.\\[4pt] [1] X.~Guan, K.~Bartschat, and B.~Schneider, Phys. Rev. A {\bf 82}, 041404 (2010).\\[0pt] [2] X.~Guan, K.~Bartschat, and B.~Schneider, Phys. Rev. A {\bf 84}, 033403 (2011).\\[0pt] [3] X.~Guan, K.~Bartschat, B.~Schneider and L.~Koesterke, Phys. Rev. A {\bf 88}, 043402(2013) [Preview Abstract] |
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K1.00142: Effect of the rotational motion between ionization and fragmentation for non-linear molecules in MFPAD studies Jesus Lopez-Dominguez, Robert Lucchese Molecular-frame photoelectron angular distributions (MFPADs) are one of the most useful quantities to measure when probing the dynamics of dissociation in photoionization. Being able to make accurate theoretical calculations of MFPADs to accompany experimental measurements is of great importance to better understand and explain the mechanisms and phenomena underlying molecular ionization and fragmentation events. One of the key approximations in determining the MFPADs assumes that the dissociative event occurs faster than the rotational motion of the molecule i.e., the axial recoil approximation. In the present work, we derived expressions for computing the usual MFPADs but including the rotational motion by accounting for the extra angular momentum dependence in non-linear molecules. This allows for the study of the recoil frame photoelectron angular distributions (RFPAD) for molecules with dissociative states where the lifetime of metastable molecular ions is not short compared to the rotational periods of the molecule. Under this consideration the number of states that can be studied is extended and a better agreement between experiment and theory is to be expected. After presenting the formalism for non-linear molecules, we used it to study the core photoionization of CH$_{4}$, and compared the results with experimental measurements and with previous works that did not include the rotational motion in the computation of the MFPADs. [Preview Abstract] |
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K1.00143: Semi-Classical Calculations of Ultracold Collisions with Frequency-Chirped Light: Dependence on Chirp Rate Matthew Wright We conduct semi-classical monte-carlo simulations of ultracold collisions utilizing frequency-chirped laser light on the nanosecond timescale. Previous work revealed partial control of light-assisted collisional mechanisms with relatively slow chirp rates (10 GHz/$\mu$s). Collisions induced with positive chirped light enhance the inelastic collisional loss rate of atoms from a magneto-optical trap whereas these trap loss collisions can be blocked when negative chirped light is used. Early quantum and classical simulations show that for negative chirps the laser's frequency continually interacts with the atom-pair during the collision. We investigate how this process depends on the chirp rate and show that by moderately speeding up the chirp ($>$ 50 GHz/$\mu$s), we can significantly enhance the difference in the collisional loss rate induced by the negative and positive chirps, gaining nearly full control of the collision. [Preview Abstract] |
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K1.00144: Superfluid - Mott transition in the presence of artificial gauge fields Ivana Vasic, Alex Petrescu, Karyn Le Hur, Walter Hofstetter Several recent cold atom experiments reported implementation of artificial gauge fields in optical lattice systems, paving the way toward observation of new phases of matter. Here we study the tight-binding model on the honeycomb lattice introduced by Haldane, for lattice bosons. We analyze the ground state topology and quasiparticle properties in the Mott phase by applying bosonic dynamical mean field theory, strong-coupling perturbation theory and exact diagonalization. The phase diagram also contains two different superfluid phases. The quasiparticle dynamics, number fluctuations, and local currents are measurable in cold atom experiments. [Preview Abstract] |
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K1.00145: Progress towards a rapidly rotating ultracold Fermi gas Ming-Guang Hu, Ruth Bloom, Deborah Jin, Eric Cornell We are designing an experiment with the goal of creating a rapidly rotating ultracold Fermi gas, which is a promising system in which to study quantum Hall physics. We propose to use selective evaporation of a gas that has been initialized with a modest rotation rate to increase the angular momentum per particle in order to reach rapid rotation. We have performed simulations of this evaporation process for a model optical trap potential. Achieving rapid rotation will require a very smooth, very harmonic, and dynamically variable optical trap. We plan to use a setup consisting of two acousto-optical modulators to ``paint'' an optical dipole trapping potential that can be made smooth, radially symmetric, and harmonic. [Preview Abstract] |
(Author Not Attending)
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K1.00146: Emulating Solid-State Physics with a Hybrid System of Ultracold Ions and Atoms Walter Hofstetter, Bissbort Ulf, Daniel Cocks, Antonio Negretti, Zbigniew Idziaszek, Tommaso Calarco, Ferdinand Schmidt-Kaler, Rene Gerritsma We propose and theoretically investigate a hybrid system composed of a crystal of trapped ions coupled to a cloud of ultracold fermions. The ions form a periodic lattice and induce a band structure in the atoms. This system combines the advantages of high fidelity operations and detection offered by trapped ion systems with ultracold atomic systems. It also features close analogies to natural solid-state systems, as the atomic degrees of freedom couple to phonons of the ion lattice, thereby emulating a solid-state system. Starting from the microscopic many-body Hamiltonian, we derive the low energy Hamiltonian, including the atomic band structure, and give an expression for the atom-phonon coupling. We discuss possible experimental implementations such as a Peierls-like transition into a period-doubled dimerized state. [Preview Abstract] |
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K1.00147: Saturation Spectroscopy in Nitrogen-Vacancy Ensembles in Diamond Pauli Kehayias, Mariusz Mr\'ozek, Victor Acosta, Andrey Jarmola, Daniel Rudnicki, Ron Folman, Wojciech Gawlik, Dmitry Budker The negatively-charged nitrogen-vacancy (NV$^-$) defect center in diamond has been used in a variety of applications, ranging from quantum information to sensing. Experiments show that the NV ground-state transitions suffer from inhomogeneous broadening, which limits the sensitivity and coherence time. To achieve narrower NV linewidths and study the sources of inhomogeneous broadening, we perform saturation spectroscopy on the NV ground-state transitions. We show that differences in magnetic field from nearby spins are the dominant source of inhomogeneous broadening in the NV ensemble, and we demonstrate that saturation spectroscopy is useful for magnetic-field-insensitive NV thermometry. [Preview Abstract] |
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K1.00148: Investigation of Molecular Structure of Porous Epoxy Thermosets via Swelling and Glass Transition Behavior Majid Sharifi, Kaustubh Ghorpade, Vijay Raman, Giuseppe Palmese Many of the excellent properties of highly crosslinked polymers are due to their molecular structures. In this study, network structures of three epoxy systems, Epon828-PACM, Epon836-PACM, and Epon1001F-PACM were investigated via equilibrium swelling theory. Each systems separately cured in presence of an inert solvent, THF, ranging from 0 to 92{\%} by volume fraction of solvent. Experimental results showed that the conventional swelling theory is valid for specimens polymerized in moderate dilute environments, i.e. up to around 60{\%} solvent by vol. whereas in extremely dilute environments, i.e. above 60{\%}, the computed M$_{\mathrm{c}}$ values are exponentially increasing. This drastic increase in M$_{\mathrm{c}}$ was investigated by T$_{\mathrm{g}}$ measurement of the polymer phase (on supercritically dried specimens). The measured M$_{\mathrm{c}}$ could not predict the corresponding T$_{\mathrm{g}}$ values according to Fox equation. Due to the highly porous nature of the resulting thermosets after supercritical drying, a modifying factor, based on the probability of finding elastic chains in a porous network, was incorporated in the conventional swelling model (Bray-Merrill equation). It was shown that the adjusted M$_{\mathrm{c}}$ values of each thermoset and the corresponding T$_{\mathrm{g}}$s are acceptably match via the well-known Fox equation. The modified M$_{\mathrm{c}}$ values indicate that, polymer networks produced in presence of miscible inert phases have relatively uniform molecular weight between crosslinks, irrespective of the amount of that inert phase. [Preview Abstract] |
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K1.00149: Emergence of Onsager vortices via evaporative heating mechanism in two-dimensional superfluid turbulence Tapio Simula, Matthew Davis, Kristian Helmerson We have studied computationally turbulent non-equilibrium dynamics of quasi-two-dimensional superfluid Bose-Einstein condensates. Beginning with a random out-of-equilibrium distribution of vortices and antivortices in the condensate, we have observed emergence of ordered vortex structures corresponding to absolute negative temperature states in this conservative Hamiltonian system. We explain the spontaneous self-organization of the singly quantized vortices into two ``Onsager vortex'' clusters of like-signed vortices in terms of an ``evaporative heating'' mechanism of the vortex gas. These results provide a clear pathway to observing Onsager vortex structures and their unusual thermodynamics in a superfluid Bose gas. [Preview Abstract] |
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K1.00150: Detailed Dissociation Dynamics Following Valence Photo-Double Ionization (PDI) of O$_{2}$ and N$_{2}$ A. Gatton, I. Bocharova, B. Gaire, A.L. Landers, Th. Weber, A. Belkacem, T. Jahnke, R. D{\"o}rner We compare the dissociation dynamics in the valence Photo-Double Ionization (PDI) of O$_{2}$ and N$_{2}$. COLd Target Recoil Ion Momentum Spectroscopy (COLTRIMS) was used to gather a kinematically complete coincidence measurement of both photoelectrons and recoil ions. PDI can occur by either direct simultaneous emission of both photoelectrons or indirectly by the ejection of a single photoelectron which leaves behind an excited cation that then undergoes autoionization. While we observe both processes in each molecule, O$_{2}$ favors the indirect and N$_{2}$ the direct path. We identify the electronic states involved with kinetic energy maps of recoil ions and electrons and with Molecular Frame Photoelectron Angular Distributions (MFPADs). We display the photoelectron relative angles to show which double ionization mechanisms are responsible for the PDI. [Preview Abstract] |
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K1.00151: ABSTRACT WITHDRAWN |
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K1.00152: An interferometer with magnetic guided Cesium atoms for inertial sensing Lu Qi, Jiancheng Fang, Zhaohui Hu, Hairong Li, Yan Wang, Zhuohuan Liu, Yuchi Zhang We discuss progress toward precision measurements of inertial forces by a magnetic guided Cesium(Cs) atom interferometer using grating echo technique. About 1e8 Cs atoms are loaded from a 2D Magneto-Optical Trap to a horizontal macroscopic magnetic guide, in which atoms float and interact with 2 pulses of standing-wave lasers. The lasers are blue detuned from 6$^{2}$S$_{1/2}$,F$=$3 $\to$ 6$^{2}$S$_{3/2}$,F$=$4 resonance and are separated by T in time. An atom density grating is formed in the vicinity of 2T, which is illuminated by a probe laser. The Bragg scattering of the probe laser is detected with balanced heterodyne technique, by which both the amplitude and phase of the density grating are obtained. The effect of acceleration and rotation can be extracted from the phase shift of the back-scattered light. The interference time is demonstrated to be prolonged with confined Cs atoms, compared to the interferometer without magnetic guide. Some properties of Cs, including recoil frequency, are measured and decoherence mechanism of Cs atoms in the magnetic guide is studied. Now we have realized interferometry in the static guide on a time scale of 2T $\sim$ 20ms. Further enhancements are anticipated by extending the interference time scale and enclosing interferometer loop. [Preview Abstract] |
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K1.00153: Optimization of Potassium-Rubidium hybrid optical pumping spin-exchange relaxation-free Magnetometer Tao Wang, Jiancheng Fang, Hong Zhang, Yang Li, Sheng Zou, Wei Quan, Heng Yuan The spin-exchange relaxation-free (SERF) magnetometer has obtained ultra-high sensitivity, which is benefited from the totally suppression of the spin-exchange relaxation. However, it is difficult to keep the alkali atoms illuminating by pumping beam with uniform pumping rate through the cell, which causes the nonuniform light shift. A SERF magnetometer with hybrid optical pumping technology was proposed in this paper, which can highly reduce the optical depth of the pump beam due to lower density of potassium gas for optical pumping. A simulation of probe beam's optical rotation with the wavelength of the probe beam was demonstrated, which matched well with the experiments, and the largest optical rotation is obtained. Benefiting from the thin optical depth, the pump beam can be exactly tuned to the D1 line. Furthermore, the optimization of the probe beam's power was proposed. When the pumping rate of the probe beam equals the spin-destruction rate, the magnetometer obtains best sensitivity. The magnetometer's linewidth was measured by using the synchronous optical pumping method. The spin-destruction rate can be calculated by the linewidth. Then, a simulation of the pump beam's pumping rate was demonstrated, the pump beam's power was optimized to achieve best sensitivity. [Preview Abstract] |
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K1.00154: Dynamically Tuned Magnetic Potentials James Stickney, Brian Kasch, Spencer Olson, Matthew Squires For many possible applications using trapped cold and ultra-cold atoms, precise control of the confining potential is required. We present a method for generating algebraically precise magnetic potentials along the axis of a cold atom waveguide. This method uses sets of paired conductors providing control over the even and odd contributions of the polynomial potential along one axis of the trap. Various field configurations can be realized, including double wells, triple wells, and filtered harmonic traps with suppression of higher order terms. The design, fabrication, and implementation of a suitable dual-layer atom chip, with modest experimental requirements will be presented. [Preview Abstract] |
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K1.00155: Ex Vacuo Atom Chips Spencer Olson, Brian Kasch, Matthew Squires Tight magnetic confinement of cold atoms is routinely achieved at sub-mm distances from the surface of an atom chip. This has led to the widespread integration of atom chips into UHV chambers so as to achieve the smallest possible atom-surface separations. We present an alternative approach in which the atom chip resides completely outside the vacuum, separated from the atoms by a thin crystalline membrane. Since replacing the atom chip does not require breaking vacuum, the swap-out time is reduced from days to minutes. This setup allows rapid prototyping of atom chip designs. We demonstrate Bose-Einstein condensation of a 87Rb cloud in this setup. [Preview Abstract] |
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K1.00156: Fabrication of Direct Bonded Copper Atom Chips for Harmonic Traps Matthew Squires, Brian Kasch, Jonathan Crow, Spencer Olson Atom chips using direct bonded copper (DBC) have greater power handling than typical lithographically produced atom chips because pure, thick (\textgreater 100 microns) copper layers are commonly obtained with DBC. We present our current fabrication techniques for DBC atom chips including: laser etching, acid etching, multi-layered chips, etc. The optimized parameters for each of these processes will be presented. Specifically, we will present the fabrication process used in the creation of a tunable harmonic trap. We will also present the design and fabrication of a chip for generating a quadrupole magnetic field for the magneto-optical trap (MOT) chip. The MOT chip is co-aligned with the harmonic trap chip to simplify transfer and optimization. [Preview Abstract] |
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K1.00157: Quantum Optomechanical Heat Engine Keye Zhang, Francesco Bariani, Pierre Meystre We investigate theoretically a quantum optomechanical realization of a heat engine. The coupling between the cavity field and the mechanical resonator results in normal mode excitations whose quantum character depends on the pump detuning and on the coupling strength. By varying that detuning it is possible to transform their character from predominantly phonon-like into photon-like modes of different frequencies and coupled to two thermal reservoirs at different temperatures. We exploit this property to propose an Otto cycle along one branch of the normal modes and calculate its total work and efficiency. We discuss basic properties of that scheme for different optomechanical systems: in the optical domain it is possible to extract work from the thermal energy of a mechanical resonator, while in the microwave range one can in principle exploit the cycle to extract work from the blackbody radiation background coupled to an ultra-cold atomic ensemble. [Preview Abstract] |
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K1.00158: Design of a Laser Ablation Ion Source for High-Precision Penning Trap Mass Spectrometry Curtis Hunt, Ishara Ratnayake, Paul Hawks, Richard Bryce, Matthew Redshaw High-precision atomic mass measurements provide important data for a wide range of fields including atomic, nuclear and neutrino physics, determination of fundamental constants, and metrology. At Central Michigan University we are building a Penning trap system that will utilize ions produced by external ion sources to allow access to a wide range of isotopes, including long-lived radioactive isotopes and isotopes with low natural abundances. The ions will be transported to a ``capture'' trap, before being transferred to double precision-measurement trap structure. In this poster we will present the design of a laser ablation ion source and the ion extraction and transport optics. We will report on the current status of the construction and operation of the ion source and the CMU Penning trap. [Preview Abstract] |
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K1.00159: Design of a double Penning-trap mass spectrometer for high-precision mass measurements Ishara Ratnayake, Richard Bryce, Paul Hawks, Curtis Hunt, Matthew Redshaw The mass of an atom plays an important role in various fields throughout science. As such, there is a need for precise mass determinations on a wide range of isotopes. At Central Michigan University we are developing a Penning trap to focus on ultra-high precision measurements of long-lived radioactive isotopes and isotopes that have low natural abundances. The Penning trap we are constructing will consist of a double precision measurement trap structure for simultaneous cyclotron frequency comparisons to eliminate the effect of magnetic field fluctuations. An additional, cylindrical Penning trap will be used to capture ions from external ion sources, eliminate contaminant ions and transfer the ions of interest to the precision traps. In this poster we will present the design of the Penning trap system, and report on the current status of the project. [Preview Abstract] |
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K1.00160: Many- and Few-Body Physics with Rydberg Polaritons in an Optical Resonator Ariel Sommer, Jonathan Simon Under conditions of electromagnetically induced transparency (EIT) with a Rydberg state, photons propagate as Rydberg polaritons--superpositions of a photon and a Rydberg excitation. We are building an experiment to study Rydberg polaritons in an optical cavity. In a near-degenerate cavity, the manifold of cavity modes provides a transverse kinetic energy and trapping potential. In this configuration, long range interactions between Rydberg polaritons give access to the crystal to superfluid phase transition. Meanwhile, working with a single or a few cavity modes yields the Rydberg blockade as a source of non-classical light, as well as few-body physics with hopping between cavity modes. The use of a high-finesse optical cavity leads to strong atom-photon coupling, protecting the polaritons from decoherence under the action of external forces and collisions. Because the kinetic energy derives from the photons, gauge fields can be introduced by engineering the cavity modes. We describe the physics of this novel system, and provide an update on the experimental progress. [Preview Abstract] |
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K1.00161: Time- and Site- Resolved Dynamics in a Circuit Topological Insulator Ningyuan Jia, Clai Owens, Ariel Sommer, David Schuster, Jonathan Simon With the discovery of the quantum Hall effect and topological insulators there has been an outpouring of ideas to harness topologically knotted band-structures in the design of state-of-the art, disorder-insensitive materials. Here we demonstrate the first simultaneous site- and time- resolved measurements of a time reversal invariant topological insulator, realized in a novel RF circuit topology. In this meta-material, we induce global topology in the band structure via local braiding in a capacitor-inductor network. We observe a gapped density of states consistent with a modified Hofstadter spectrum at a flux per plaquette of $\phi=\pi/2$. In-situ probes reveal spatial localization within the bulk energy-gaps, as well as de-localized edge states. Time-resolved dynamics demonstrate a splitting of localized excitations into spin-resolved edge-modes. The RF circuit paradigm is naturally compatible widely proposed non-local coupling schemes, allowing us to implement a Mobius topological insulator inaccessible to conventional materials. Combining local braiding in an RF circuit with circuit-QED techniques, provides a direct path to topologically ordered quantum phases of matter. [Preview Abstract] |
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K1.00162: An Apparatus for Studying Rydberg Polaritons in an Optical Resonator Alexander Georgakopoulos, Albert Ryou, Ningyuan Jia, Nathan Schine, Aaron Krahn, Graham Greve, Ariel Sommer, Jonathan Simon, Lindsay Bassman In electromagnetically induced transparency (EIT) involving a Rydberg state, the dark state polaritons, or Rydberg polaritons, consist of a superposition of an atomic Rydberg excitation and a photon. Rydberg polaritons offer a route towards realizing long-range interactions in a quantum-degenerate atomic and optical system. The Rydberg component gives rise to strong, long-range van der Waals interactions between polaritons, while the photonic component determines the kinetic energy of the polaritons. We report on progress towards the realization of a two-dimensional quantum gas of Rydberg polaritons in a high finesse optical cavity. The strong atom-light coupling in the cavity suppresses decoherence arising from atomic motion, polariton collisions, and the photonic kinetic energy. A sufficient polariton lifetime gives access to coherent quantum many-body physics, including the phase transition between a superfluid and crystalline ground state and few-body blockade effects. [Preview Abstract] |
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K1.00163: Fiber Alkali Vapor Laser R. Ayachitula, N. Hafner, R.J. Knize Free-space optically pumped alkali lasers have demonstrated high efficiency, good beam quality and scalability to high powers. Fibers have the potential to guide such high power beams for long distances. Combining these two technologies, we demonstrate an optically pumped alkali vapor laser in a hollow fiber where rubidium and methane have been allowed to migrate throughout the hollow core fiber. By end-pumping rubidium in our fiber at the 780 nm, 5S$_{1/2} \to$ 5P$_{3/2}$ D2 line, create a population inversion between the 5P$_{1/2}$ and 5S$_{1/2}$states from state-mixing via methane buffer gas and lase on the 795 nm D1 line. [Preview Abstract] |
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K1.00164: Surface-enhanced quantum control of three-level systems Chitra Rangan, Christopher DiLoreto Noble-metal nanoparticles can be used to enhance state decay rates in proximate quantum systems and to control local electromagnetic fields. In this paper, we show that this surface enhancement can be used to improve the preparation of desired target quantum states. We model the interaction between a three-level quantum system with an incident electromagnetic wave in proximity to a gold nanoparticle. We show that by placing a three-level quantum system near a gold nanoparticle, we can use an electromagnetic wave to control the quantum dynamics in a reduced period of time and with a lower electric field intensity when compared to an isolated system. This reduction in required time, electric field intensity and the ability to modify system purity may represent an improvement in the practical control and use of quantum information systems. [Preview Abstract] |
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K1.00165: Breaking time reversal symmetry in a circuit topological insulator Clai Owens, Ningyuan Jia, Ariel Sommer, David Schuster, Jonathan Simon Materials exhibiting knotted band-structures provide a unique window on interplay between topology and quantum mechanics under well-controlled conditions. The main difficulty is engineering a strong background gauge field for the electrically neutral ``particles'' that comprise such materials. In cold atom systems, the leading candidates include Raman couplings, lattice modulation, and optical flux lattices; however no scalable approach has yet been demonstrated. Meta-materials have seen substantial success, both in coupled optical waveguides, and circuit networks. Here we describe progress towards time reversal breaking in a circuit, to split up- and down- spin Chern bands. This work is essential for studies of fractional quantum hall physics, where spin-flip collisions effectively reverse the magnetic field and destroy the many-body state. We present the design of a 1D transmission line that breaks time reversal symmetry via periodic capacitance modulation. We extend this approach to a 2D geometry, realizing a Floquet topological insulator with an isolated ground Chern-band. These tools are compatible with circuit quantum electrodynamics techniques, and thus provide an exciting route to studies of topologically ordered phases of matter. [Preview Abstract] |
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K1.00166: Even-odd spatial nonequivalence for atomic quantum gases with isotropic spin-orbit couplings G.S. Singh, Reena Gupta A general expression for the density of states (DOS) of power-law trapped $d$-dimensional ideal quantum gases with isotropic spin-orbit couplings (SOCs) is derived and is found to bifurcate into even-$d $and odd-$d$ classes. The expressions for the grand potential and hence for several thermodynamic quantities are then shown to be amenable to exact analytical forms provided $d$ is an odd integer. Also, a condition $\gamma < 2d$ is obtained in case of odd-$d$ for appearance of the Bose-Einstein condensation with $\gamma$ as the power-law exponent. It is thus established that isotropic SOCs render even and odd dimensional spaces nonequivalent for uniform as well as trapped gases, and that the DOS of one-dimensional (1D) ideal gases, uniform or trapped, remains unaffected by the SOC. Furthermore, the analytical study of the transition temperature and the condensate fraction in a 3D Bose gas under combined presence of the harmonic trapping and the Weyl coupling shows that the condensation is favored by the former but disfavored by the latter. This countering behavior is discussed to be in conformity with the exchange-symmetry-induced statistical interactions resulting from these two entities as enunciated recently [Phys. Rev. A \textbf{88}, 053607 (2013)]. [Preview Abstract] |
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K1.00167: High sensitivity magnetometry with Cs vapor Rujie Li, Jiancheng Fang, Wei Quan Spin-exchange relaxation free(SERF) magnetometry based on potassium has broken the magnetic field sensitivity record previously kept by the superconducting quantum interference devices (SQUIDs). We describe a Cs atomic magnetometer also operating in SERF regime. Utilizing a cubic profile, about a 2cm on a side, vapor cell with a relative low temperature of 106 degrees, we achieve the resonance linewidths 2.703Hz corresponding to an electron spin-exchange rate of 357 /s, and demonstrate magnetic field sensitivity of 8 fT/Hz$^{1/2}$ in a single channel. Theoretical analysis shows that fundamental sensitivity limits of this device with a 1 cm$^{3}$ volume could approach 0.2 fT/Hz$^{1/2}$. Taking advantage of the higher saturated vapor pressure, Cs magnetometry is particularly appropriate for lower temperatures applications. [Preview Abstract] |
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K1.00168: Experimental observation of entanglement duality for identical particles Jiajun Ma, Xinxing Yuan, Xiuying Chang, Panyu Hou, Chong Zu, Luming Duan It was shown recently that entanglement of identical particles has a feature called dualism [Phys.Rev. Lett. 110, 140404 (2013)], which can be used to test quantum indistinguishability without bringing the particles together. Here we report an experiment that observes the entanglement duality for the first time with two identical photons, which manifest polarization entanglement when labeled by different paths or path entanglement when labeled by polarization states. By adjusting the mismatch in frequency or arrival time of the entangled photons, we tune the photon indistinguishability from quantum to classical limit and observe that the entanglement duality disappears under emergence of classical distinguishability, confirming it as a characteristic feature of quantum indistinguishable particles. [Preview Abstract] |
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K1.00169: Experimental test of state-independent quantum contextuality of an indivisible quantum system Meng Li, Yun-Feng Huang, Dong-Yang Cao, Chao Zhang, Yong-Sheng Zhang, Bi-Heng Liu, Chuan-Feng Li, Guang-Can Guo Since the quantum mechanics was born, quantum mechanics was argued among scientists because the differences between quantum mechanics and the classical physics. Because of this, some people give hidden variable theory. One of the hidden variable theory is non-contextual hidden variable theory, and KS inequalities are famous in non-contextual hidden variable theory. But the original KS inequalities have 117 directions to measure, so it is almost impossible to test the KS inequalities in experiment. However bout two years ago, Sixia Yu and C.H. Oh point out that for a single qutrit, we only need to measure 13 directions, then we can test the KS inequalities. This makes it possible to test the KS inequalities in experiment. We use the polarization and the path of single photon to construct a qutrit, and we use the half-wave plates, the beam displacers and polar beam splitters to prepare the quantum state and finish the measurement. And the result prove that quantum mechanics is right and non-contextual hidden variable theory is wrong. [Preview Abstract] |
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K1.00170: Electron-photon interaction near the surface of a planar target Moses Fayngold A photon in a momentum eigenstate, incident on an inhomogeneous screen, produces the superposition of an infinite number of evanescent states (ES) near the screen's surface. Accordingly, the two different types of ES (or evanescent waves) named as EW1 and EW2 are described in 2 respective experimental setups: 1) total internal reflection and 2) scattering on an inhomogeneous planar target. Some interactions are considered between an EW2-photon and the environment. The latter may include a beam of probing particles and/or the screen on which the EW2 are formed. Some new properties of ES are described, such as complex energy eigenvalues in case of a movable screen, and evanescence exchange between the interacting objects. This reveals the connection between ES and the Gamow states of the studied system. The energy-momentum exchange between EW2 and the probe (e.g., an electron) is highly selective and may collapse the superposition of photon EW2- eigenstates to a single EW-eigenstate of the probing particle. Possible imprints of EW2 in the far field are briefly discussed and a simple experiment is suggested for their observation. [Preview Abstract] |
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K1.00171: Ab initio electron collisions with $N^+_2$: Application to dissociative recombination Duncan Little, Jonathan Tennyson Extensive ab initio scattering calculations have been performed using the well established R-matrix method to comprehensively map out the electronic structure of N$_2$ above and below the ionisation threshold. Advances in computational efficiency meant it was possible to use a fine grid of internuclear separations to characterise the many avoided crossings and complex mixing of valence and Rydberg type states brought about the proximity of the ground and first excited state. It was shown that with this approach, a scattering calculation outperforms a standard multireference configuration interaction with respect to the calculation of Rydberg states. This is the most comprehensive study of the electronic structure of N$_2$ to date and sets a benchmark for future calculations of Rydberg--valence type states. The R-matrix method provides a self-consistent means to find all of the parameters needed to find a dissociative recombination (DR) cross-section. These parameters have now been used to calculate a cross-section for the DR of N$^+_2$ using multi-channel quantum defect theory including so called ``core-excited'' Rydberg states. The calculated cross-section is completely ab initio and agrees well with experiment at low electron energies. [Preview Abstract] |
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K1.00172: Electrical Resistive Heaters for Magnetically Sensitive Instruments Michael Bulatowicz US Patent 8,138,760 ``Temperature System with Magnetic Field Suppression'' describes design concepts and examples for development of electrical resistive heaters and temperature detectors suitable for temperature control of the alkali vapor cells of magnetically sensitive atomic instruments such as spin-exchange relaxation free (SERF) magnetometers. This is achieved through careful manipulation of electromagnetic multi-pole moments in the design of these resistive heaters for substantial self-cancellation of electrically generated magnetic fields. The magnetic performance of electrical resistive heaters produced according to these design principles and directly attached to a rubidium vapor cell has been demonstrated to cause no measurable degradation of the performance of a SERF magnetometer exhibiting noise below 2 femto-Tesla per square root Hz. [Preview Abstract] |
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K1.00173: Dipolar gases of ground state molecules: NaK in Hannover Matthias W. Gempel, Torben A. Schulze, Torsten Hartmann, Ivo I. Temelkov, Horst Kn\"ockel, Alessandro Zenesini, Eberhard Tiemann, Silke Ospelkaus In the coming years, dipolar interactions will be one of the most promising tools in the field of ultracold atoms. Since the first realization of degenerate gases of dipolar atoms and the creation of large diatomic molecular samples in their rovibrational groundstate [1], a lot of experimental and theoretical interest has been focused on long-range interactions, anisotropy, exotic phase transitions and other peculiar phenomena. We will update you on our work in Hannover with details on the NaK experimental apparatus and on our effort to determine the most efficient adiabatic transfer from weakly-bound dimers to ground state dipolar molecules [2]. \\[4pt] [1] K.-K. Ni et al, Science 322, 231 (2008).\\[0pt] [2] T.A.Schulze et al, Phys. Rev. A 88, 023401 (2013) [Preview Abstract] |
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K1.00174: ABSTRACT WITHDRAWN |
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K1.00175: Convenient and reliable fabrication of high surface quality tungsten electrodes for ion trap Zhao Wang, Karthik Thadasina, Kim Qian, Ji Liu, Yunfeng Huang, Le Luo We present a new electrochemical etching method for mass-production of tungsten tips as ion trap electrodes, which can also be employed for fabricating nanoscale probes and fiber micro-lens for Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (STM) and Microelectromechanical Systems (MEMS). Using inexpensive, convenient material and equipment in the process, a simple procedure yields sharp, uniformly shaped and robust tips. Furthermore, the shape and size are tweaked by selecting appropriate electrolyte solution concentration and voltage to produce tips with arbitrary shape. We also explore optimal parameters to create consistent tungsten tips for Ion-Trap experiments. This technique paves the way for the mass-production of ion trap based quantum computer systems. [Preview Abstract] |
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K1.00176: The Phase-Amplitude (Ph-A) representation of a wave function, revisited George Rawitscher A very attractive feature of the Ph-A description $\psi $(r) $=$ y(r) sin($\varphi $ (r)) is the slowly varying monotonic nature of both the amplitude y(r) and the phase $\varphi $(r) as a function of distance r, even though the wave function may be highly oscillatory. The solution of Milne's non-linear equation for y(r) is done iteratively, using a spectral representation for y in terms of Chebyshev polynomials. For an example with a long range potential of the form 1/r$^{3}$ , an accuracy of better than 1{\%} is achieved over a radial interval from 0 to 3000 units of length, requiring only 64 mesh points. Advantages of the Ph-A representation are a) the storage memory compression, b) the calculation of a scattering wave function for very long range potentials, and c) the economy in the calculation of overlap matrix elements under certain conditions. [Preview Abstract] |
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K1.00177: Quantum Quench of a P-wave Fermi Gas Sukjin Yoon, Gentaro Watanabe We investigate the non-equilibrium dynamics following a quantum quench in a single-species superfluid Fermi gas at zero temperature. This p-wave Fermi gas is known to undergo a quantum phase transition when the inter-particle interaction is changed from the BCS to BEC regime, which is distinct from a crossover in the s-wave case. The quench dynamics of polar states of the p-wave superfluid Fermi gas is studied within a mean field approach. The time evolutions of the order parameter and the momentum occupation are obtained and compared with the s-wave case. [Preview Abstract] |
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K1.00178: Experimental and Numerical Study of Bright Matter- Wave Soliton Collisions H. Luo, J.H.V. Nguyen, P. Dyke, R.G. Hulet We create pairs of bright matter-wave solitons from Bose-Einstein condensates of $^7$Li atoms by tuning the scattering length to a negative value. We examine the collision of a pair of solitons formed in a quasi-$1$-D harmonic trap as a function of their relative phase. While the solitons pass through one another without change in shape or amplitude, they nonetheless exhibit an effective interaction that can be either repulsive or attractive depending on their relative phase. Furthermore, we observe a discontinuous jump in the soliton motion that causes the dipole mode oscillation frequency to shift to values greater than the trap frequency. The result is compared to numerical solution of the $3$-D Gross-Pitaevskii equation. [Preview Abstract] |
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K1.00179: From weakly to strongly interacting 2D Fermi gases Paul Dyke, Kristian Fenech, Marcus Lingham, Tyson Peppler, Sascha Hoinka, Chris Vale We study ultracold 2D Fermi gases of $^6$Li formed in a highly oblate trapping potential. The potential is generated by a cylindrically focused, blue detuned TEM01 mode laser beam. Weak magnetic field curvature provides highly harmonic confinement in the radial direction and we can readily produce single clouds with an aspect ratio of 230. Our experiments investigate the dimensional crossover from 3D to 2D for a two component Fermi gas in the Bose-Einstein Condensate to Bardeen Cooper Schrieffer crossover. Observation of an elbow in measurements of the cloud width vs. atom number is consistent with populating only the lowest transverse harmonic oscillator state for weak attractive interactions. This measurement is extended to the strongly interacting region using the broad Feshbach resonance at 832 G. We also report our progress towards measurement of the 2D equation of state for an interacting 2D Fermi gas via in-situ absorption imaging. [Preview Abstract] |
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K1.00180: Quantum Turbulence Arising from Countersuperflow Instability in Miscible Two-component Bose-Einstein Condensates Hiromitsu Takeuchi, Shungo Ishino, Makoto Tsubota Turbulence is one of the great unsolved problems in physics. Quantum turbulence (QT) in superfluids is expected to give a prototype of turbulence much simpler than usual classical turbulence and has recently become one of the most important fields in low-temperature physics. Recent development of experimental technique enable us to study QT in atomic Bose-Einstein condensates (BECs). Recently, we proposed that countersuperflow, a flow state of miscible superfluids with a relative velocity, can lead to turbulence after the characteristic instability development of vortex nucleation and vortex reconnection in miscible two-component BECs [1, 2]. QT of two-component BECs can provide another prototype of turbulence because eddies in classical turbulence may be mimicked by vorticity distribution without singularity in this system. In this presentation, we will report on our numerical analysis of the parameter dependence of the statistical property, such as energy spectrum and enstrophy distribution, of the QT arising from countersuperflow instability (CSI) in two-component condensates. [1] Hiromitsu Takeuchi, Shungo Ishino, and Makoto Tsubota, Phys. Rev. Lett. 105, 205301 (2010). [2] Shungo Ishino, Makoto Tsubota, and Hiromitsu Takeuchi, Phys. Rev. A 83, 063602 (2011). [Preview Abstract] |
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K1.00181: Countersuperflow in Binary Bose-Einstein Condensates with Rabi Coupling Hiromitsu Takeuchi, Ayaka Usui Countersuperflow instability, dynamic instability of counterflow of miscible superfluids, was observed recently for the first time by Hamner et al. [1]. In the experiment, a countersuperflow of miscible two-component Bose-Einstein condensates (BECs) was realized in a quasi-one-dimensional trap by applying a magnetic gradient, which leads to a force in opposite directions for each component. A countersuperflow becomes dynamically unstable if the relative velocity between two superfluids exceeds a critical value and the instability causes characteristic density patterns forming solitons in quasi-one-dimensional systems. Very recently, Hamner et al. performed the experiment in a similar situation where a two-component BEC is subject to inhomogeneous Rabi oscillations between two pseudospin components under a magnetic gradient [2]. Motivated by the experiment, we investigated stability of countersuperflow with internal Josephson coupling, namely, Rabi coupling. We reveal the stability phase diagram of countersuperflow with Rabi coupling. [1] C. Hamner, J. J. Chang, P. Engels, and M. A. Hoefer, Phys. Rev. Lett. 106, 065302 (2011). [2] C. Hamner, Yongping Zhang, J. J. Chang, Chuanwei Zhang, and P. Engels, Phys. Rev. Lett. 111, 264101 (2013). [Preview Abstract] |
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K1.00182: A novel experiment for coupling a Bose-Einstein condensate with two crossed cavity modes Tobias Donner, Julian Leonard, Moojnoo Lee, Andrea Morales, Thomas Karg, Tilman Esslinger Over the last decade, combining cavity quantum electrodynamics and quantum gases allowed to explore the coupling of quantized light fields to coherent matter waves, leading e.g. to new optomechanical phenomena and the realization of quantum phase transitions. Triggered by the interest to study setups with more complex cavity geometries, we built a novel, highly flexible experimental system for coupling a Bose-Einstein condensate (BEC) with optical cavities, which allows to switch the cavity setups by means of an interchangeable science platform. The BEC is generated from a cloud of laser-cooled 87-Rb atoms which is first loaded into a hybrid trap, formed by a combined magnetic and optical potential, and then optically transported into the cavity setup, where it is cooled down to quantum degeneracy. At first we aim to explore the coupling of a BEC with two crossed cavity modes. We report on our progress on the implementation of a science setup involving two cavities intersecting under an angle of 60$^{\circ}$. his setup will allow us to study the coherent interaction of a BEC and the two cavity modes both in internal lambda-level transitions and in spatial self-organization processes in dynamical hexagonal lattices. [Preview Abstract] |
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K1.00183: Techniques for reconstructing the column-density of a Bose-Einstein condensate from multiple defocused images Abigail Perry, Seiji Sugawa, Francisco Salces-Carcoba, Ian Spielman We report on an experiment reconstructing the column-density of a Bose-Einstein condensate using differently defocused images from multiple cameras. Starting with defocused images taken off-resonance, a transfer function with a ``not-quite invertible'' relationship exists, going from the optical depth observed at the camera to the focused column density [L.D. Turner et al., Opt. Lett., 29(3) 232-234 (2004)]. Adding additional defocused detectors allows us to fully reconstruct the focused image, and more advanced techniques allow us to reconstruct both the amplitude and phase of the electromagnetic wave at the image planes. [Preview Abstract] |
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K1.00184: Design and Implementation of a Fast Imaging System for Detection of Optical Lattices Matthew Gillette, Andrew Hachtel, Ethan Clements, Shan Zhong, Ray Ducay, Samir Bali A home built system for imaging optical lattices is presented. Our imaging system uses a repurposed astronomy camera- the complete system costs less than {\$}5000 while rivaling the performance of a commercially available system which costs {\$}40-50000. The camera must have an extremely low dark current, high quantum efficiency, as well as the ability to take precisely timed millisecond exposures. Using LabVIEW a sequence of precise electronic pulses is created to control the laser beams in order to load the lattice structure with cold atoms. When running a LabVIEW VI at millisecond timescales Windows introduces inaccuracies in pulse timing. A master slave computer setup, called a real time target (RTT) is created in order to increase this accuracy to the microsecond level. [Preview Abstract] |
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K1.00185: Designing Ratchets in Ultra-cold Atoms for the Advanced Undergraduate Laboratory Andrew Hachtel, Matthew Gillette, Ethan Clements, Shan Zhong, Rey Ducay, Samir Bali We propose to perform ratchet experiments in cold Rubidium atoms using state-of-the-art home-built tapered amplifier and imaging systems. Our tapered amplifier system amplifies the output from home-built external cavity tunable diode lasers up to a factor 100 and costs less than {\$}5,000, in contrast to commercial tapered amplifier systems, which cost upward of {\$}20,000. We have developed an imaging system with LabVIEW integration, which allows for approximately 2 millisecond exposures and microsecond control of experimental parameters. Our imaging system also costs less than {\$}5,000 in comparison to commercial options, which cost between {\$}40-50,000. Progress toward implementation of a one-dimensional rocking ratchet is described. [Preview Abstract] |
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K1.00186: Electromagnetically Induced Transparency Experiments for the Advanced Undergraduate Laboratory: Suppression of Polarization Impurity and Stray Magnetic Fields Kaleb Campbell, Richard Jackson, Matthew Van Vleet, Kodi Kuhnash, Bradley Worth, Amanda Day, Samir Bali We investigate electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) in rubidium vapor using a single laser beam and a scanning magnetic field co-aligned with the laser propagation direction. We show that polarization impurity, stray magnetic fields and imperfect optical alignments cause broadening of the EIT/EIA signal and other spurious effects. We describe a systematic approach to minimizing these undesired effects, which produces EIT/EIA signals nearly two orders of magnitude narrower than the natural linewidth. [Preview Abstract] |
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K1.00187: Novel Bio, Chemical, Environmental Sensing Based on New Model of Total Internal Reflection in Turbid Media Samir Bali, Patrick Judge, Nathan Phillip, Jordan Boivin, Jonathan Scaffidi, Jason Berberich, Lalit Bali We have initiated a collaborative experimental research program that combines new advances in optical physics, field portable chemical analysis, and biosensing. Our goal is to discover and characterize new optical sensing methodologies in opaque, highly scattering (i.e., ``turbid'') media, and demonstrate new paradigms for optical sensing in research and industry. We have three specific objectives. First, we propose to fully characterize and validate a new model of total internal reflection (TIR) from highly turbid media thus enabling a first demonstration of non-invasive, in-situ, real-time particle sizing for the case of arbitrary scattering particle size--a holy grail in colloidal science. Second, we propose to implement a first demonstration of real-time non-invasive measurement of nanoparticle aggregation in highly turbid media. Third, we propose to use our new sensing methodology to demonstrate real-time in-situ label-free monitoring of molecular interactions and adsorption at surfaces. [Preview Abstract] |
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K1.00188: An Improved Antihydrogen Trap Rita Kalra, Stephan Ettenauer, Nathan Jones, William Kolthammer, Robert McConnell, Philip Richerme, Eric Tardiff, Gerald Gabrielse The recent demonstration of trapped atomic antihydrogen for 15 to 1000 seconds is a milestone towards precise spectroscopy for tests of CPT invariance. The confinement of a total of 105 $\pm$ 21 atoms in a quadrupole magnetic trap was made possible by several improved methods. Improved accumulation techniques give us the largest numbers of constituent particles yet: up to 10 million antiprotons and 4 billion positrons. A novel cooling protocol leads to 3.5 K antiprotons, the coldest ever made. Characterizing and controlling the geometry and density of these confined antimatter plasmas allow for consistency in antihydrogen production. Continued use of these methods, along with the larger trap depth of a unique second-generation magnet, are expected to yield greater numbers of trapped antihydrogen. The new magnet generates both quadrupole and octupole trap geometries, which can reduce charged particle loss and prove useful for laser cooling and spectroscopy. The ultra-low inductances of the magnet lead to vastly reduced turn-off times, required for single-atom detection. The successful operation of the magnet and its turnoff times has been experimentally demonstrated. [Preview Abstract] |
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K1.00189: ABSTRACT WITHDRAWN |
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K1.00190: Breakdown of Landau's Fermi liquid theory in a Strongly Interacting Fermi Gas Tara Drake, Yoav Sagi, Rabin Paudel, Deborah Jin We present a novel measurement of the single particle spectral function for a homogeneous Fermi gas above the critical temperature throughout the BCS-BEC crossover. We observe that the dispersion can be fitted extremely well by a function composed of two parts: the spectral function of bound pairs and that of a Landau Fermi liquid (FL). We find that already at unitarity, the FL theory is largely unsuited to describe the data, which exhibits a predominantly pair-like dispersion. For diminishing attractive interactions, the spectral function converges to that expected by a FL, from which we get the effective mass of the fermionic quasiparticle. Our data reconciles different past experimental observations by showing how the many-body behavior of fermions in the BCS-BEC crossover changes from a FL to a molecular Bose gas over a rather small region. [Preview Abstract] |
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K1.00191: Quantum metrology frontiers with highly squeezed quantum states of atomic ensembles Onur Hosten, Nils J. Engelsen, Rajiv Krishnakumar, Mark A. Kasevich Production of spin-squeezed atomic ensembles could greatly enhance the performance of existing atom-based sensors by overcoming the atomic shot-noise that limits these sensors. At the time of writing, our preliminary results with an ensemble of 25x10$^{3}$ $^{87}$Rb atoms (prepared in magnetically insensitive states) suggest a noise reduction that is 17dB below shot-noise with 90{\%} coherence indicating a metrologically relevant squeezing parameter of 16.5dB. With our currently known experimental inefficiencies the theoretical maximum we expect to observe lies around 23dB for 100x10$^{3}$ atoms. We employ a measurement based squeezing method inside of a high-finesse (\textgreater 10$^{5}$) dual-wavelength cavity, resonant at both 780 nm (probe) and 1560 nm (trap). The commensurate wavelength relationship allows identical coupling of the probe light to all atoms, generating symmetric squeezed states, opening up the future possibility of releasing the generated states into free-space for fluorescence detection, compatible with atomic fountain based sensors. [Preview Abstract] |
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