Bulletin of the American Physical Society
40th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 54, Number 7
Tuesday–Saturday, May 19–23, 2009; Charlottesville, Virginia
Session T1: Poster Session III (4:00 - 6:00 pm) |
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Room: Newcomb Hall Ballroom |
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T1.00001: ATOMIC AND MOLECULAR STRUCTURE AND PROPERTIES |
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T1.00002: Experimental Studies of NaCs S.T. Ashman, C.M. Wolfe, J.P. Huennekens We present experimental studies of excited electronic states of the NaCs molecule that are currently underway in our laboratory. The optical-optical double resonance method is used to obtain Doppler-free excitation spectra for several excited states. These data are being used to obtain Rydberg-Klein-Rees (RKR) or Inverse Perturbation Approach (IPA) potential curves for these states. We are also trying to map the bound portion of the 1($a)^{3}\Sigma ^{+}$ potential using resolved laser-induced fluorescence and Fourier transform spectroscopy to record transitions into the shallow well. Bound-free spectra from single ro-vibrational levels of electronically excited states to the repulsive wall of the 1($a)^{3}\Sigma ^{+}$ state are also being recorded. Using the previously determined excited state potentials, we can fit the repulsive wall of the 1($a)^{3}\Sigma ^{+}$ state to reproduce the experimental spectra using LeRoy's BCONT program. A slightly modified version of BCONT will also be used to fit the relative transition dipole moments, \textit{$\mu $}$_{e}(R)$, as a function of internuclear separation $R$, for the various bound-free electronic transitions. [Preview Abstract] |
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T1.00003: Using hyperfine structure to investigate perturbations between highly-excited states: the HF C-X spectrum Jeffrey Philippson, Ralph Shiell, Elmar Reinhold, Wim Ubachs It has long been known that the B $^1\Sigma^+$ ion-pair state in HF is strongly perturbed by electronic Rydberg states [1]. We present a quantitative analysis of these perturbations through their effects on the fluorine orbital magnetic hyperfine parameter obtained from XUV spectra of the C $^1\Pi$, $v$=0-X $^1\Sigma^+$, $v$=0 transition [2]. A $\Lambda$-doubling interaction between the ground vibrational level of the C-state and the nearby $v$=29 level of the B-state produces an apparent rotational state dependence in the values of this parameter derived from the R-branch lines. This work demonstrates how insight into the extent of inter-state perturbations can be obtained from the variation of hyperfine parameters.\\[4pt] [1] A. E. Douglas and F. R. Greening, Can. J. Phys. {\bf 57}, 1650 (1979).\\[0pt] [2] J. N. Philippson, R. C. Shiell, E. Reinhold and W. Ubachs, J. Chem. Phys. {\bf 129}, 174310 (2008). [Preview Abstract] |
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T1.00004: Atom-diatom intermolecular forces and three body dispersion coefficients for doublet Li${}_3$ Jason N. Byrd, John A. Montgomery, H. Harvey Michels, Robin Cote We calculate {\em ab initio} the ground state interaction potential surface for the lithium doublet trimer for both long range and near equilibrium geometries. A variety of methods are used to calculate the interaction energy, including complete active space SCF, full valence configuration interaction and coupled cluster theories as appropriate. Interpolation between {\em ab initio} points is accomplished with a dual-level interpolant moving least squares fitting algorithm using a scaled gaussian weight function. The global potential energy surface is found to have a large three-body interaction contribution. The atom-diatom dispersion coefficients ($C^ {\lambda}_n(r,\theta)$) for long range interactions ($R\gg r $) are found by fitting to the {\em ab initio} surface. [Preview Abstract] |
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T1.00005: Study of Low-Z EUV Spectra from Laboratory Plasma and EBIT Experiments P.G. Wilcox, A.S. Safronova, V.L. Kantsyrev, A.A. Esaulov, U.I. Safronova, K.M. Williamson, G.C. Osborne, M.E. Weller, J. Clementson, P. Beiersdorfer, J. Lepson This paper provides an analysis of recent experimental EUV and soft x-ray Oxygen and Carbon spectra from the NSTX, SSPX, compact laser facility ``Sparky'', and EBIT-I plasma devices. Additionally, Nitrogen lines in EUV spectra from EBIT-I are identified and used to benchmark a Nitrogen kinetic model. In this study, non-LTE kinetic models of C, N, and O are utilized. Our approach compares the features of experimental spectra from Tokamak, Spheromak, and EBIT with those from ``Sparky'' spectra generated under various plasma conditions. The emitted EUV radiation we examine generally falls in the 90 {\AA} to 260 {\AA} wavelength range. Furthermore, the most intense lines from He-like ions of C and O in the soft X-ray region (20 {\AA} - 40 {\AA}) are observed. This research is being supported by DOE under grant DE-FG02-08ER54951 and in part under NNSA Cooperative Agreements DE-FC52-06NA27588 and DE-FC52-06NA27586. Work at LLNL was performed under auspices of the DOE under contract DE-AC52-07NA2344. [Preview Abstract] |
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T1.00006: Separation of binary gas mixtures flowing through small orifices Rainer Johnsen, Barun K. Chatterjee Many atomic collision experiments rely on sampling of atoms, molecules or ions from a differentially-pumped gas cell via a small orifice into a separate analysis chamber. In such experiments the question arises if and to what extent the composition of a gas mixture is altered by the differential outflow of gases through the orifice, which is often in the transition regime between molecular and hydrodynamic flow. Somewhat surprisingly, gas separation effects of this kind are poorly understood and many experimenters seem to be unaware of them, even though ignoring them can cause serious errors. In this poster, we report results of drift-tube measurements, in which we used ion-molecule reactions to determine the variation of the number density of a minority molecular gas in the presence of a lighter or heavier rare gas. We find that the concentration of a heavier minority gas is far more strongly suppressed than one might estimate on the basis of simple mean-free-path arguments. While we have not succeeded in devising a theory of the effect (which may be amenable only to computer simulations), we show that a simple semi-empirical formula reproduces observations reasonably well. [Preview Abstract] |
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T1.00007: Quantum critical point in high-temperature superconductors Miron Amusia, Vasiliy Shaginyan Recently, in high-temperature superconductors (HTSC), exciting measurements have been performed revealing their physics in superconducting and pseudogap states and in normal one induced by the application of magnetic field, when the transition from non-Fermi liquid to Landau Fermi liquid behavior occurs (T. Shibauchi, et al., Proc. Natl. Acad. Sci. USA 105, 7120 (2008)). We show that in the pseudogap regime (when the superconductivity vanishes) the pairing of electrons (or the formation of preformed electron pairs) takes place, while the gap continues to follow a simple d-wave form. These observations are in accord with recent facts (H.-B. Yang, et al., Nature 456, 77 (2008)). We employ a theory, based on fermion condensation quantum phase transition which is able to explain facts obtained in the measurements. We also show, that in spite of very different microscopic nature of HTSC, heavy- fermion metals and 2D $^3$He, the physical properties of these three classes of substances are similar to each other. It follows from our study that there is at least one quantum phase transition inside the superconducting dome, and this transition is the fermion condensation quantum phase transition. [Preview Abstract] |
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T1.00008: Energy scales and magnetoresistance at a quantum critical point Miron Amusia, Vasiliy Shaginyan The magnetoresistance (MR) of CeCoIn55 is notably different from that in many conventional metals. We show that a pronounced crossover from negative to positive MR at elevated temperatures and fixed magnetic fields is determined by the scaling behavior of quasiparticle effective mass. At a quantum critical point (QCP) this dependence generates kinks (crossover points from fast to slow growth) in thermodynamic characteristics (like specific heat, magnetization etc) at some temperatures when a strongly correlated electron system transits from the magnetic field induced Landau Fermi liquid (LFL) regime to the non-Fermi liquid (NFL) one taking place at rising temperatures. We show that the above kink-like peculiarity separates two distinct energy scales in QCP vicinity - low temperature LFL scale and high temperature one related to NFL regime. We show that the same behavior is observed under the application of elevated magnetic field at fixed temperature. These observations are in accord with recent facts (P. Gegenwart, et. al., Science 315, 969 (2007)). Our comprehensive theoretical analysis of experimental data permits to reveal for the first time new MR and kinks scaling behavior as well as to identify the physical reasons for above energy scales. [Preview Abstract] |
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T1.00009: Progress towards a permanent electron electric dipole moment search using cold atoms in an optical lattice Neal E. Meyer, Kunyan Zhu, Fang Fang, David S. Weiss Observation of a permanent electric dipole moment of the electron would imply CP violating effects not contained in the Standard Model. We present our progress towards measuring the electron EDM using laser-cooled cesium and rubidium atoms trapped in a one dimensional optical lattice. We have launched laser-cooled Cs atoms in a cavity-enhanced optical lattice guide. We re-cool and re-trap the atoms in the 90 cm high measurement region, obtaining an overall transfer efficiency from the magneto-optic trap of 50\%. We will describe the development of two such lattices in parallel, passing between specially-coated fused silica electric field plates. [Preview Abstract] |
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T1.00010: FUNDAMENTAL SYMMETRIES AND PRECISION MEASUREMENTS |
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T1.00011: Blackbody-radiation shift in a $^{88}$Sr$^+$ ion optical frequency standard Dansha Jiang, Bindiya Arora, Marianna Safronova, Charles W. Clark The blackbody radiation (BBR) shift of the $5s - 4d_{5/2}$ clock transition in $^{88}$Sr$^+$ is calculated using the relativistic all-order method where all single and double excitations of the Dirac-Fock wave function are included to all orders of perturbation theory. The BBR shift is a major component in the uncertainty budget of the optical frequency standard based on $^{88}$Sr$^+$ trapped ion at room temperature. Additional calculations are conducted for the dominant contributions in order to evaluate some omitted high-order corrections and estimate the uncertainty of our final value. The scalar polarizabilities of the $5s$ and $4d_{5/2}$ levels, as well as the tensor polarizability of the $4d_{5/2}$ level, are presented together with the evaluation of their uncertainties. The lifetimes of the $4d_{3/2}$, $4d_{5/2}$, $5p_{1/2}$, and $ 5p_{3/2}$ states are calculated and compared with experimental values. [Preview Abstract] |
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T1.00012: Investigation of the optical transition in the $^{229}$Th nucleus: Solid-state optical frequency standard and fundamental constant variation Wade Rellergert, David DeMille, Eric Hudson We describe a novel approach to directly measure the energy of the low-lying isomeric state in $^{229}$Th. This unique nuclear transition is low enough in energy that it can be studied by laser spectroscopy. Since nuclear transitions are far less sensitive to environmental conditions than atomic transitions, it is shown that the $^{229}$Th atoms can be interrogated inside a suitable host crystal without significantly impacting the transition linewidth. The technique might also allow for the construction of a solid-state optical frequency standard that surpasses the precision of current optical clocks, as well as improved limits on the variability of fundamental constants. [Preview Abstract] |
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T1.00013: Precise measurements of hyperfine structure and atomic polarizability in indium and thallium using two-color diode laser spectroscopy. P.K. Majumder, Mevan Gunawardena, Huajie Cao, Scott Smedinghoff We are pursuing a series of precise atomic structure measurements in Group III elements -- currently thallium and indium -- designed to test recent \textit{ab initio} theory calculations in these three-valence-electron systems [Phys. Rev. A 74, 022504 (2006); Phys. Rev. A 76, 022501 (2007)]. For thallium, independent atomic theory calculations are essential for atomic tests of discrete symmetry violation. In an experiment just completed, we used two-step, two-color laser excitation to measure the hyperfine constants of the 6P$_{3/2 }$excited state of indium(I=9/2) for the first time. Currently we are pursuing a similar two-step excitation experiment in thallium to measure the isotope shift and hyperfine splitting in the 7P$_{1/2}$ excited state using a heated quartz vapor cell. In both experiments, the blue laser for the first excitation step is locked to its transition using a new scheme which makes use of an acousto-optic modulator. The thallium optical system will next be used with our thallium atomic beam apparatus to measure the Stark shift of the thallium 1301 nm 7S$_{1/2 }$- 7 P$_{1/2}$ transition. Future experiments may include using a laser near 400 nm to study the light shift in the ground state hyperfine splitting of another Group III element (gallium) which has been proposed as a possible neutral atom frequency standard. [Preview Abstract] |
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T1.00014: Tests of Fundamental Symmetries Using a Compact, Rotating Co-Magnetometer Justin Brown, Sylvia Smullin, Thomas Kornack, Michael Romalis A K-$^3$He co-magnetometer contains overlapping, coupled ensembles of high-density polarized K vapor and polarized $^3$He nuclei. An appropriately applied magnetic field cancels the $^3$He magnetization allowing for magnetometer operation in the highly sensitive spin-exchange relaxation free (SERF) regime. The resulting co-magnetometer is insensitive to magnetic fields, but sensitive to electron and neutron couplings to anomalous fields. The compact, second generation co-magnetometer is mounted on a rotary platform for reorientation of the sensitive direction in the lab frame. We present data in which we periodically rotate the experimental apparatus 180$^\circ$ every $\approx 1$ min in search of CPT and Lorentz violating fields passing through our celestial frame. We discuss important systematic effects involved with reversals of the entire experiment such as axial tilt and a gyroscope signal from Earth's rotation. The compact assembly also facilitates searches for proposed long range spin-dependent forces. A polarized electron spin source containing $\approx 10^{25}$ spins can be placed $\approx25$ cm from the co-magnetometer and rotated every $\approx20$ s to search for new spin-dependent forces between electrons. [Preview Abstract] |
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T1.00015: Progress Towards an Electron EDM Search Using Trapped Molecular Ions Laura Sinclair, Huanqian Loh, Russell Stutz, Eric Cornell A sample of trapped molecular ions can provide large effective electric fields and long electron spin coherence times in the search for a permanent electron electric dipole moment (EDM). We plan to use the $^3\Delta_1$ state of trapped HfF$^+$ in this search. The $^3\Delta_1$ state should yield effective internal fields of $\sim$10 V/cm and should be easily polarized in $\sim$1 V/cm electric fields due to the small $\Omega$-doublet splitting. Confinement of the ions in a linear Paul trap allows for long electron spin coherence times and thus increased sensitivity. We will report on preliminary HfF$^+$ spectroscopy and other experimental progress. [Preview Abstract] |
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T1.00016: Progress Towards Measurement of the Electron Electric Dipole Moment Using the PbF Molecule: Measurement of Hyperfine Splittings Poopalasingam Sivakumar, Christopher McRaven, Milinda Rupasinghe, Neil Shafer-Ray The lead monofluoride molecule provides for a 1000- to 10,000- fold improvement in sensitivity to an electron electric dipole moment (e-EDM) over atomic-based measurements. An understanding of details of the electronic structure of the ground state of PbF is critical to quantify this sensitivity. The hyperfine constants of the molecule provide an unique test of our understanding of the ground-state wave function of the molecule. Here we present a comparison of our latest measurements to previous predictions. [Preview Abstract] |
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T1.00017: Search for the electric dipole moment of the electron with ThO Yulia V. Gurevich, Wesley C. Campbell, David DeMille, John M. Doyle, Gerald Gabrielse, Nicholas Hutzler, Maxwell Parsons, Benjamin Spaun, Amar C. Vutha The thorium monoxide (ThO) molecule in its metastable H state has been identified as a promising system for measuring the permanent electric dipole moment of the electron (eEDM). We have begun an experiment to measure the eEDM using a high flux, cryogenic beam of ThO. We report our progress, including the production of cold ThO beams with an observed flux of $2 \times 10^{9}$ molecules per ablation shot. We also demonstrate optical pumping of molecules into the H state, which allows us to make a more accurate determination of the H state lifetime. [Preview Abstract] |
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T1.00018: Electroweak Physics in Molecules E. Deveney, R. Paolino, M.G. Kozlov, J. Barry, S.B. Cahn, D. Murphree, D. Rahmlow, M. Steinecker, C.G. Yale, D. DeMille We report on recent progress of our program to measure nuclear spin-dependent parity nonconservation (NSD-PNC) in electron-nucleon interactions.~ We probe enhanced NSD-PNC signals from the mixing of rotational/hyperfine states in diatomic molecules that are Zeeman shifted to near degeneracy.~ The NSD-PNC effect arises from two main sources: the electron-vector/nucleon-axial $\left( {V_e A_n } \right)$ tree-level neutral current (a $Z^0$-mediated coupling parameterized by electroweak constants $C_{\left\{ {2P,N} \right\}} )$, and a hyperfine term resulting from coupling of the nuclear anapole moment (a magnetic moment induced by intra-nuclear electoweak interactions) to the electron's magnetic dipole moment.~ The $V_e A_n $ term is independ. of the nucleon number $A$ of a given nucleus and is suppressed in the Standard Model, while the anapole term scales as $A^{\raise0.5ex\hbox{$\scriptstyle 2$}\kern-0.1em/\kern-0.15em\lower0.25ex\hbox{$\scriptstyle 3$}}$making it the dominant source of NSD-PNC in nuclei with$A>20$.~ Measurements in molecules containing nuclei over a large range of $A$ should allow us to disentangle the two NSD-PNC contributions, increasing available data on nuclear anapole moments and reducing uncertainties in current measurements of $C_{2P} $ and $C_{2N} $.~ Progress includes demonstration of an increased-flux molecular beam source, and a substantial improvement of molecular detection efficiency using a new scheme. [Preview Abstract] |
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T1.00019: Current status of the measurement of the anapole moment Dong Sheng, Adrian Perez Galvan, Jonathan Hood, Luis Orozco We present the current status of the experimental effort towards the measurement of the anapole moment in different isotopes of francium. The anapole is a parity-violating, time-reversal conserving nuclear moment that arises from the weak interaction among nucleons. Due to the electromagnetic interaction between electrons and nucleons, atomic physics gives the unique possibility to probe the weak interaction in the low energy regime. Our experimental scheme involves driving a parity forbidden E1 transition between hyperfine ground states in a series of francium isotopes inside a blue detuned dipole trap at the electric antinode of a microwave cavity. The experiment will make use of the ISAC radioactive beam facility at TRIUMF. The system is currently being tested with rubidium. [Preview Abstract] |
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T1.00020: SPECTROSCOPY, LIFETIMES, AND OSCILLATOR STRENGTHS |
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T1.00021: Precise Measurement of the Isotope Shift of the Lithium D Lines Clayton E. Simien, John D. Gillaspy, Craig J. Sansonetti High precision spectroscopic measurements of the isotope shift of low-lying lithium transitions can be combined with precise theoretical calculations to probe the relative nuclear charge radii of various lithium isotopes. The technique is of particular interest for exotic lithium isotopes for which traditional scattering experiments are not feasible. Despite several recent experiments, however, the measured isotope shifts for the D1 and D2 lines of the stable isotopes $^{6}$Li and $^{7}$Li remain in strong disagreement with each other and with theory. Reported values for the splitting isotope shift (SIS), the difference between the isotope shifts of the D1 and D2 lines, disagree with theory by as much as 16 standard devitions. This is particularly significant, as the SIS is believed to be the most reliable result of theory. In order to resolve these discrepancies we are constructing a new experiment at the National Institute of Standards and Technology. As in other experiments we will observe the D lines by crossing a highly collimated lithium beam with a very stable tunable laser. Unlike previous experiments, however, the relative positions of all lithium resonances will be determined by direct frequency metrology. Our results should provide precise new values for the fine structure, hyperfine structure, and isotope shifts of the lithium D lines and a definitive test of the calculated SIS. [Preview Abstract] |
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T1.00022: Precision measurement of the lifetime of the $6p \mbox{ } {}^{2}P_{1/2}$ level of Yb${}^{+}$ S. Olmschenk, D. Hayes, D.N. Matsukevich, P. Maunz, C. Monroe We present a precise measurement of the lifetime of the $6p \mbox{ } {}^{2}P_{1/2}$ excited state of a single trapped ytterbium ion (Yb${}^{+}$). We use a time-correlated single photon-counting technique~\footnote{L. Young, \textit{et al}., \textit{Phys. Rev. A} \textbf{50}, 2174 (1994)} adapted to utilize the features of a single-atom system~\footnote{D. L. Moehring, \textit{et al.}, \textit{Phys. Rev. A} \textbf{73}, 023413 (2006)}. In particular, ultrafast pulses excite a single trapped Yb$^+$ ion and the emitted photons are coupled into a single-mode optical fiber. By performing the measurement on a single atom with fast excitation and excellent spatial filtering, we are able to eliminate common systematics. Among other things, experimental measurements of Yb-like ions may be used to test \textit{ab initio} atomic structure calculations~\footnote{U. I. Safronova, \textit{et al.}, \textit{Phys. Rev. A} \textbf{66}, 022507 (2002)}. [Preview Abstract] |
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T1.00023: Single atom Rydberg spectroscopy and AC Stark shifts in two-photon excitation Erich Urban, Thomas Henage, Larry Isenhower, Todd Johnson, Thad Walker, Mark Saffman We have developed an instrument that allows spectroscopy of Rydberg states to be performed on single, optically trapped atoms. Two-photon excitation of single Rb atoms is used to measure dynamic (AC) Stark shifts of the ground to Rydberg transition. The measured shifts are compared with theoretical calculations. The influence of the AC Stark shifts on the fidelity of Rydberg gate operations is discussed, and we present a simple method for canceling the Stark shifts by balancing the single photon excitation Rabi frequencies. [Preview Abstract] |
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T1.00024: Hyperfine-induced Intercombination Transitions $n^3{\rm D}_1$ to $2^1{\rm P}_1$ in $^3$He$^*$ Gordon Drake, Qixue Wu In heliumlike ions with nuclear spin, the electric dipole transition $2\;^3{\rm P}_J\rightarrow1\;^1{\rm S}_0$ is allowed since hyperfine interaction causes mixing between two hyperfine states with different $J$ but the same $F$ (due in part to fine-structure interactions for $J=1$). Since the pioneering works of Garstang and Mohr, the hyperfine-induced intercombination transition has been a subject of experimental and theoretical interest. However, previous works treated only the more highly charged He-like ions ($Z\geq 6$) since the singlet-triplet mixing caused by hyperfine interaction is so small for low-$Z$ ions that the induced intercombination line $2\;^3{\rm P}_J\rightarrow1\;^1{\rm S}_0$ is difficult to observe. In contrast, we have found theoretically that for $^3$He ($Z=2$), the hyperfine-induced intercombination transitions $n\;^3{\rm D}_1(F=3/2) \rightarrow 2\; ^1{\rm P}_1(F=1/2)$ with higher $n$ have comparable intensities to normal E1 transitions between two hyperfine states. The calculated results show that hyperfine-induced intercombination transitions contribute 46 percent $(n=10)$, and 35 percent $(n=9)$ of all E1 transitions $^3{\rm D}_1(F=3/2) \rightarrow 2\;^{1,3}{\rm P}_J(F)$. Similar results of this induced transition have been obtained as well for $^3{\rm D}_1(F=3/2)$ $\rightarrow$ $n\; ^1{\rm P}_J(F)$ with $n=3$ to $10$. High precision variational calculations in Hylleraas coordinates of the line strength will be presented. [Preview Abstract] |
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T1.00025: Measurement of the Electron Affinity of Arsenic and the Fine Structure of As$^{- }$ C.W. Walter, N.D. Gibson, R.L. Field III, J.Z. Shapiro, A.P. Snedden, C.M. Janczak, D. Hanstorp The electron affinity of arsenic and the negative ion fine structure splittings of As$^{-}$ have been measured using tunable laser photodetachment threshold spectroscopy. The relative cross section for neutral atom production was measured with a crossed laser-ion beam apparatus over selected photon energy ranges between 0.63 -- 0.82 eV. An $s$-wave threshold was observed due to the opening of the As$^{-}$ (4$p^{4}$ $^{3}P_{2})$ to As (4$p^{3} \quad ^{4}S_{3/2})$ ground state to ground state transition, yielding a preliminary value for the As electron affinity of 0.80481(13) eV. $s$-wave thresholds were also observed for detachment from the J = 0 and J = 1 excited levels of As$^{-}$, yielding preliminary values for the fine structure splittings of 0.1276(2) eV for $^{3}P_{1}$ -- $^{3}P_{2}$ and 0.1643(6) eV for $^{3}P_{0}$ -- $^{3}P_{2}$. The values measured in the present work are consistent with previous measurements [1,2] and substantially reduce the uncertainties. [1] T.P. Lippa \textit{et al}., J. Chem. Phys. \textbf{109}, 10727 (1998); [2] G. Haeffler \textit{et al.}, Z. Phys. D \textbf{42}, 263 (1997). [Preview Abstract] |
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T1.00026: Excitation of the 5$p$-8$p$ Electric Quadrupole Transition in Cold Rb Atoms Rico Pires, Marco Ascoli, Edward Eyler, Philip Gould We have observed the electric-dipole (E1) forbidden, but electric-quadrupole (E2) allowed, 5$p$-8$p$ transition in a sample of ultracold $^{87}$Rb atoms. The 5$p_{3/2}$ level is populated by a diode laser at 780 nm, while the 5$p_{3/2}$ to 8$p_{1/2,3/2}$ transition is driven with a dye laser at 587 nm. We have performed the experiment both with cw dye laser excitation and with pulsed amplification ($\sim $7 ns) of this cw light. In both cases, the 8$p$ atoms are detected by pulsed photoionization. With cw excitation, we can easily resolve the 5$p$ and 8$p$ hyperfine structures. By comparing transitions from the 5$p_{3/2}$, \textit{F$^{\prime}$}=0 level to 8$p_{1/2}$ levels with \textit{F$^{\prime \prime}$}=1 and 2, we can set a limit on the weak magnetic-dipole (M1) contribution to the transition strength.\footnote{S.B. Bayram, et al., Phys. Rev. A 62, 012503 (2000).} This work is supported by NSF. [Preview Abstract] |
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T1.00027: Lifetimes of Metastable $2\;^3{\rm S}_1$ States of Heliumlike Ions Gordon Drake, Paul Moffatt The lifetime of the $2\,^3{\rm S}_1$ state of helium is unusually long. This property is useful in astrophysical observations of nebulae to determine their temperature and density conditions. Calculations of relativistic magnetic dipole (M1) transitions, including corrections to the magnetic dipole transition operator, are performed and the lifetimes for the metastable $2\,^3{\rm S}_1$ state are evaluated. These decay rates for heliumlike ions have been calculated by Drake [1]. The present work provides an update to the calculations using significantly larger basis sizes in the calculation, yielding more accurate results. M1 decay rates are presented for all the heliumlike ions through the isoelectronic sequence up to Fe XXV. These results can be compared with measurement by Moos and Woodworth [2], and the electron beam ion trap results tabulated by Tr\"abert [3].\\[6pt] \mbox{}[1] G.W.F. Drake, Phys. Rev. A {\bf 3}, 3 (1971).\\ \mbox{}[2] H.W. Moos and J.R. Woodworth, Phys. Rev. A {\bf 12}, 2455 (1975).\\ \mbox{}[3] E. Tr\"abert, Can. J. Phys. {\bf 86}, 73 (2008). [Preview Abstract] |
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T1.00028: Precision Lifetime Measurement of the Cesium 6P$_{3/2}$ State Jerry Sell, Brian Patterson, Randy Knize, Thomas Ehrenreich We will report the final results from our precision measurement of the cesium 6P$_{3/2}$ atomic state lifetime. The measurement technique consists of an initial pulse ($\sim$ nJ) selected from a mode-locked Ti:Sapphire laser which excites cesium atoms in counter-propagating thermal beams to the cesium 6P$_{3/2}$ state. A subsequent laser pulse is amplified in a regenerative amplifier ($\sim$ $\mu$J) and also frequency doubled, resulting in pulses which nonresonantly ionize the cesium atoms in the 6P$_{3/2}$ state. The ions are collected and counted while varying the delay between the excitation and ionization pulses allowing us to measure the excited state lifetime. Dominant systematic errors in the measurement include: effects from the misalignment of the excitation and ionization laser beams, quantum beats in the photoionization detection, and radiation trapping affecting the observed lifetime. These systematic errors along with others are examined which lead to a total systematic error of 0.04$\%$. Currently our statistical error of 0.1$\%$ results in a total measurement uncertainty of 0.11$\%$, making these among the most precise direct measurements of an atomic lifetime. [Preview Abstract] |
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T1.00029: Emission Lines of Fe XI - XIII in the Extreme Ultraviolet Region Jaan Lepson, Peter Beiersdorfer, Duane Liedahl, Priya Desai, Nancy Brickhouse, Andrea Dupree, Steven Kahn Iron is one of the most abundant heavy elements in extreme ultraviolet spectra of astrophysical and laboratory plasmas, and its various ions radiate profusely in the extreme ultraviolet (EUV) wavelength band. Iron emission in the EUV provides important d iagnostic tools for such properties as plasma temperature and density, and perhaps even magnetic field strength. Despite its importance to astrophysics and magnetic fusion, knowledge of the EUV spectrum of iron is incomplete. Identification of iron emis sion lines is hampered by the paucity of accurate laboratory measurements and the uncertainty of even the best atomic models. As part of a project to measure and compile emission line data in the EUV, we present here spectra and lines of Fe XI - XIII recorded on the Livermore EBIT-II electron beam ion trap in the 50 - 120 \AA\ region. We measured line positions to 0.02 \AA\ and relative intensities with an accuracy of one part in twenty. Many new lines are identified and added to the available databa ses. Part of this work was performed under the auspices of the U S Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and was supported by NASA's Astronomy and Physics Research and Analysis Program under Con t ract NNH07AF811. [Preview Abstract] |
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T1.00030: ATOMIC, MOLECULAR, AND CHARGED PARTICLE COLLISIONS |
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T1.00031: Large cross sections for transitions with a small energy difference J.H. McGuire, Kh. Kh. Shakov Cross sections for transitions between states with small differences in energy can be quite large. An example is the 1s-2p transition in atomic hydrogen caused by the impact of a fast charged particle [1] or a photon [3]. In such cases the actual cross section may become much larger than the simple geometric cross section. Such transitions are often difficult to observe in the laboratory. However, they can be evaluated numerically. This effect can be significant in analysis of astrophysical data, as pointed out by T. Nandi [2]. I discuss a few examples of calculations and give a physical explanation for this effect. \\[4pt] [1] J.H. McGuire, D. J. Land, J. G. Brennan and G. Basbas, Phys. Rev. \textbf{A19}, 2180 (1979).\\[0pt] [2] Kh.Kh. Shakov and J.H. McGuire, Phys. Rev. \textbf{A67} 033405 (2003). \\[0pt] [3] T. Nandi, private communication, 2008. [Preview Abstract] |
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T1.00032: Isotopic effects in slow elastic and inelastic $He^{2+}+H$collisions P.S. Krstic, N. Stolterfoht We study isotopic effects in slow (10-400 eV) collisions of alpha-particle with hydrogen using a fully quantal Hidden Crossings Coupled Channel approach [Krstic, J. Phys. B. 37, L217 (2004)]. A strong presence of the Coriolis transitions in the studied energy range as well as a competition with the radial transitions create a number of strong and unexpected isotopic effects [Stolterfoht et al, Phys. Rev. Lett. 99, 103201 (2007)] in both inelastic (charge transfer and excitation) and elastic collisions. P.K. acknowledges support from the US DOE Office of Fusion Sciences through ORNL, under contract No. DE-AC05-00OR22725 with UT-Battelle, LLC. [Preview Abstract] |
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T1.00033: K-x-ray emission in MeV/u O$^{5+}$ on Ar collisions T. Elkafrawy, J.A. Tanis K-X-ray emission has been investigated for 1.5 and 2 MeV/u O$^{5+}$ on Ar collisions. Emission lines resulting from O-K$\alpha $, Ar-K$\alpha $ and Ar-K$\beta $ transitions have been observed. This work was done at Western Michigan University using the tandem Van de Graaff. For oxygen, the observed x rays may be attributed to K-shell excitation and in the case of Ar to excitation or ionization. The K-x-ray production cross sections have been determined taking into account the detector solid angle and detection efficiency, and are compared with related measurements from other investigators. Coincidence measurements are planned to investigate in detail the K-x-ray production mechanisms. [Preview Abstract] |
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T1.00034: REACTIVE SCATTERING AND RECOMBINATION PROCESSES |
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T1.00035: Theoretical Studies of Dissociative Recombination D.O. Kashinski, R.F. Malenda, A.P. Hickman, D. Talbi We are currently investigating the dissociative recombination (DR) of electrons with the molecular ions $\mathrm{N}_2\mathrm{H}^+$ and and $\mathrm{C}_3\mathrm{H}_3^+$. These ions exist in the interstellar medium, and accurate DR rate constants are needed for astrophysical models. We are performing large scale electronic structure calculations of the excited-state potential surfaces of $\mathrm{N}_2\mathrm{H}$ necessary to treat the process $e^- + \mathrm{N}_2\mathrm{H}^+ \rightarrow \mathrm{N}_2 + \mathrm{H}$ or $\mathrm{N} + \mathrm{NH}$. The work is based on using the block diagonalization method to determine diabatic potential curves. The dissociating curve that governs DR is then easily identified, and off-diagonal coupling terms can be used to determine the autoionization width $\Gamma$ that is essential for a dynamics calculation. The status of the calculations will be presented at the conference. We have also investigated the normal modes of the molecular ion $\mathrm{C}_3\mathrm{H}_3^+$. We expect that energy flow into and out of the vibration of a single CH bond may influence the overall DR dynamics, and we account for this effect using an appropriate quantum mechanical wave function for the initial state. [Preview Abstract] |
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T1.00036: ELECTRON-ATOM COLLISIONS |
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T1.00037: Electron and positron scattering using the confined variational method Jun-Yi Zhang, Jim Mitroy, Kalman Varga The phase shifts of a scattering Hamiltonian can be determined from the discrete energies of same Hamiltonian calculated with the addition of an artificial confining potential. The general formalism required to perform calculations on scattering states with non-zero angular momentum and on molecular systems is outlined. Calculations on real systems with correlated basis sets have given phase shifts for the electron and positron scattering from hydrogen and helium that are more precise than any previously published. The first results for calculations on molecular systems will be presented. [Preview Abstract] |
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T1.00038: Effects of Polarization and Electron Correlation on the Electron Impact ionization of Helium atom Haripada Saha We have extended the multi-configuration Hartree-Fock (MCHF) method [1] for electron impact ionization of atoms to investigate the effects of both polarization [2] and electron correlation of the target in the initial state on the electron impact ionization of atoms. To determine the importance of electron correlation between the two outgoing continuum electrons in the final state we have performed calculations in the HF and the vatiationally determined screening potential approximations [3-5]. We will report results of our calculation of triple differential cross sections for electron impact ionization of helium atom at excess energies $\le $ 4 eV for the coplanar geometry for equal and unequal energy sharing of the two outgoing electrons. We will compare our results with the available experimental measurements and other theoretical calculations. [1] H.P. Saha (unpublished], [2] H.P. Saha, Phys. Rev. Lett. \textbf{65}, 2003 (1990), [3] M.R.H. Rudge and Seaton, Proc. R. Soc., London, Ser. A\textbf{283}, 262 (1965), [4] R.K. Peterkop, Theory of ionization of atoms by electron impact (Colorado Associated University Press, Boulder, (1977)), pp. 128 and 129. [5] Cheng Pan and Anthony F. Starace, Phys. Rev. Lett. \textbf{67} , 185 (1991); Phys. Rev. A \textbf{45} , 4588 (1992). [Preview Abstract] |
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T1.00039: Electron impact excitation cross sections into (4p)$^{5}$5p and (5p)$^{5}$6p levels from the (4p)$^{5}$5s and (5p)$^{5}$6s metastable levels of Kr and Xe respectively by the Kim B-E-f Scaling method M.A. Ali, P.M. Stone We present results for electron impact excitation cross sections from the (4p)$^{5}$5s, 1s$_{5}$ and 1s$_{3}$ metastable levels of Kr to the (4p)$^{5}$5p, 2p$_{1}$ to 2p$_{10}$ levels, which are dipole allowed. We use the B-E-f Scaling procedure of Kim [1] with the experimental excitation energy and accurate f values from experiment and other advanced theoretical calculations. We compare our results with apparent excitation cross sections recently reported by Jung et al. We study the importance of cascade contributions by comparing our results with experiment and relativistic distorted wave results of Srivastava et al. Corresponding metastable level excitation cross sections in Xe are reported and compared with experiment and the recent relativistic distorted wave results of Jiang et al. [1] Y-K. Kim Phys. Rev. A \textbf{64} 032713 (2001). [Preview Abstract] |
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T1.00040: Low-Energy Electron Elastic Cross Sections for Lanthanide Atoms Z. Felfli, A.Z. Msezane, D. Sokolovski Dramatically sharp resonances characterize the near-threshold electron elastic scattering total cross sections for the lanthanide atoms, whose energy positions are identified with the binding energies (BEs) of the negative ions formed during the collisions as Regge resonances. The recently developed Regge-pole methodology which naturally embodies the crucial electron correlation effects together with a Thomas-Fermi type potential incorporating the vital core-polarization interaction are used for the calculations[1]. The extracted BEs of the lanthanide negative ions vary from 0.016 eV for Tm$^{-}$ to 0.631 eV for Pr$^{-}$. All the negative ions of the lanthanides can be classified as weakly bound (BEs $<$ 1.0 eV), while only three are tenuously bound (BEs $<$ 0.1 eV) [2]. Ramsauer-Townsend minima, shape resonances and the Wigner threshold behavior for these lanthanides are also determined. Extracted EAs for La and the open d- and f- sub-shell Ce atoms agree excellently with the measured data [3, 4] while for Nd and Eu the agreement with calculated values [5] is outstanding. [1] D. Sokolovski et al, Phys. Rev. A76, 012705 (2007) [2] Z. Felfli et al, Phys. Rev. A 79, At Press (2009) [3] A. M. Covington et al, J. Phys. B 31, L855 (1998) [4] C.W. Walter et al, Phys. Rev. A 76, 052702 (2007) [5] S.M. O'Malley and D.R. Beck, Phys. Rev. A78, 012510 (2008) Supported by U.S. DOE, Division of Chemical Sciences. [Preview Abstract] |
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T1.00041: Complex $q$ parameters for helium $L=0,1,2$ autoionizing levels N.L.S. Martin, B.A. deHarak, K. Bartschat We recently reported\footnote{B.A. deHarak, K. Bartschat, and N.L.S. Martin, {\em Phys. Rev. Lett.}, {\bf 100}, 063201 (2008).} out-of-plane \ee\ experiments on He autoionization. The data were presented as angular distributions of ejected electrons from the three autoionizing levels $^1S_0$, $^1D_2$, and $^1P_1$ and exhibited two well known features, the binary and recoil peaks. It was found that the recoil peak (relative to the binary peak) could be accurately reproduced by a second order distorted wave Born calculation using the $R$-matrix with pseudo-states approach, but not by the equivalent {\it first order} calculation, which underestimated the size of the recoil peak. It was also found that a plane wave Born approximation calculation could reproduce the results, but only if anomalously large values of Fano $q$-parameters were assumed. We will present an analysis of the first and second order calculations in terms of Fano $q$ parameters. We find that for the first order calculations the $q$ parameters are essentially real, but for the second order calculations they are complex, quantities. The $^1D_2$ parameters are particularly striking in this respect. [Preview Abstract] |
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T1.00042: Hybrid theory for P-wave scattering of electrons from helium ions A.K. Bhatia The hybrid theory has been applied to the S-wave scattering of electrons from H atoms,\footnote{A.K.Bhatia, Phys. Rev. A 75, 032713 (2007)} and He$^+$ and Li$^{++}$ ions.\footnote{A.K.Bhatia, Phys. Rev. A 77, 052707 (2008)} In this method, both the short-range and long-range correlations are included in the Scrodinger equation at the same time. Phase shifts obtained in this method have rigorous lower bounds to the exact phase shifts. Now this method is being extended to the P-wave scattering of electrons from helium ions. At lower energies, the phase shifts obtained are very close to those obtained using the Feshbach projection operator formalism.\footnote{A.K.Bhatia, Phys. Rev. A 73, 012705 (2006)} But at higher energies, there is disagreement which is not understood. [Preview Abstract] |
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T1.00043: Fully relativistic B-spline R-matrix calculations for electron collisions with mercury Oleg Zatsarinny, Klaus Bartschat We have applied our recently developed fully relativistic Dirac $B$-spline $R$-matrix (DBSR) code~[1] to calculate electron scattering from mercury atoms. Results from a \hbox{36-state} close-coupling calculation are compared with numerous experimental benchmark data for angle-integrated and angle-differential cross sections, as well as spin-asymmetry, spin-polarization, and electron-impact coherence parameters. We generally obtain significant improvement in the agreement between experiment and theory compared to previous distorted-wave and close-coupling attempts. [1] O.~Zatsarinny and K.~Bartschat, Phys. Rev. A {\bf 77}, 062701 (2008). [Preview Abstract] |
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T1.00044: COLLISIONS INVOLVING ANTIMATTER |
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T1.00045: Positron-molecule binding energies C.M. Surko, J.R. Danielson, J.A. Young Positron annihilation on many molecular species occurs via vibrational Feshbach resonances thus indicating that positrons bind to these molecules\footnote{J. A. Young and C. M. Surko, {\it Phys. Rev. A} {\bf 77}, 052704 and {\bf 78}, 032702 (2008).}. The downshifts in these resonances from the energies of the molecular vibrational modes provide a measure of the positron-molecule binding energy, $\epsilon_b$. To date, binding energies for thirty molecular species have been measured using this technique$^2$. This paper describes a regression analysis of the dependence of $\epsilon_b$ on molecular parameters. A reasonably accurate model can be constructed using a weighted, linear combination of the dipole polarizability, permanent dipole moment, and the number of $\pi$ bonds for the molecule. The resulting expression is used to compare with existing theoretical predictions of $\epsilon_b$. In some cases the predictions are within a factor of two, while in others, they are off by as much as an order of magnitude. Tests of the model to predict molecules that do not bind positrons, interesting molecules for future study, and other possible parameterizations of $\epsilon_b$ will also be discussed. [Preview Abstract] |
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T1.00046: High-lying P-wave resonances in PS-H scattering below the p+Ps$^-$ threshold Zong-Chao Yan Yan, Y.K. Ho Here, we present a calculation of P-wave resonances lying below the p + Ps$^-$ threshold by using the method of complex- coordinate rotation [1]. The present work is a continuation of our recent investigation of high-lying S-wave resonances in Ps- H scattering below the same p+Ps$^-$ threshold [2]. Using elaborate Hylleraas wave functions in which all the six inter- particle coordinates are included [3], resonance energies and widths for several lower members of a Rydberg series are calculated. At the meeting, we will compare our results with those of an earlier calculation [4].\\[4pt] [1] Y. K. Ho, Phys. Rept. 99, 1 (1983), and references therein.\\[0pt] [2] Z.-C. Yan and Y. K. Ho, Phys. Rev. A 77, 030701 (2008).\\[0pt] [3] Z.-C. Yan and G. W. F. Drake, J. Phys. B. 30, 4723 (1997). \\[0pt] [4] J. Di Rienzi and R. J. Drachman, Phys. Rev. A 76, 032705 (2007). [Preview Abstract] |
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T1.00047: Progress Towards a Positronium Beam Kay Pelletier, Jason Engbrecht To date, work with positronium (Ps) has required either indirect statistical measurements or analysis done with high ($>$10 eV) kinetic energy beams. Here we propose a low energy Ps beam that will allow for investigation of fundamental questions concerning Ps, such as gas scattering cross-sections and condensed matter surface interactions.~ These results may also improve material science analysis techniques by providing a better theoretical basis for pore analysis of materials.~ Using a new nanotube material we predict that positrons incident on the tubes will form positronium and be emitted at thermal energies in a well-collimated beam. In order to produce this beam we require a low noise, time tagged, and focused positron beam. To achieve a low background rate we use a bent magnetic field to filter out fast unmoderated positrons from the beam. A bunching circuit provides a timing signal for incidence on the nanotubes. Due to parasitic capacitances, significant transformations to the input waveform were required to achieve the ideal bunching waveform. Finally a neodymium magnet was used to focus the positrons onto a small spot on the nanotubes. [Preview Abstract] |
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T1.00048: Monte Carlo simulation of thermalziation of positronium in helium and water vapour Srdjan Marjanovic, Zoran Petrovic Thermalization of positronium in helium and water vapour is modeled by a Monte Carlo simulation. Recently, positron transport was modeled by modern Monte Carlo codes since the data for binary collisions became available. Those studies are the basis for calculations for distributions of emitted gamma rays in living tissue and materials that are subject to positron emission diagnostics. Similar collisional data would be needed to follow the positronium which is formed in the last stage of positron interaction with gases and liquids. Measurements of positrinium thermalization yielded data that were analyzed to produce the scattering cross sections in helium [1] by using energy Balance equations with an assumption of Maxwell Boltzmann distribution (MBD) function for positronium. We have used a Monte Carlo code and tested cross sections without any assumptions for the energy distribution function. The thermalization of the initial distribution is rapid which supports the choice of MBD. Spatial ranges of penetration as well as diffusion coefficients were also determined. Similar calculations were made for water vapour based on the cross sections presented in [2]. [1] J J Engbrecht et al. Phys. Rev. A 77, 012711 (2008) [2] F A Gianturco et al. Phys. Rev. A 64 032715 (2001) [Preview Abstract] |
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T1.00049: AMO REALIZATIONS OF CONDENSED MATTER MODELS |
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T1.00050: Interacting Bosonic and Fermionic Atoms in 3D Optical Lattice Potentials Sebastian Will, Thorsten Best, Simon Braun, Ulrich Schneider, Lucia Hackerm\"{u}ller, Immanuel Bloch Mixtures of ultracold gases form novel quantum many-body systems offering unique experimental controllability. Depending on interaction strength, number of particles and temperature, these systems can display rich phase diagrams with close analogies to condensed matter physics. Particularly in the presence of a periodic potential, such mixtures are expected to show the formation of anti-ferromagnetic ordering, charge-density waves, polaron-like quasi-particles or even supersolid-ordering. In our 3D optical lattice setup we investigate both Fermi-Fermi mixtures formed by two distinct spin states of ${}^{40}$K as well as Bose-Fermi mixtures consisting of ${}^{87}$Rb and ${}^{40}$K atoms. In the case of Fermi-Fermi mixtures we have directly measured the compressibility of the quantum many-body system. This allowed us to identify metallic, Fermi liquid and insulating phases. For strong interactions, evidence for an emergent incompressible Mott-insulating phase was found. On the side of Bose-Fermi mixtures we could elucidate effects of interspecies interactions by analysing long-range phase coherence properties and performing absolute measurements of interaction energies using quantum phase diffusion. The current status of our projects will be presented. [Preview Abstract] |
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T1.00051: 2D Surface Trap for Quantum Simulation Jonathon Gillen, Waseem Bakr, Amy Peng, Simon F\"olling, Markus Greiner We present a novel optical trapping scheme for low dimensional quantum gases. Using a combination of evanescent waves, standing waves, and magnetic potentials we create a 2D Bose-Einstein condensate at a distance of only a few microns away from a glass surface. The trapping potentials near the surface are smooth and allow for a highly anisotropic confinement with an aspect ratio of 300:1:1 as well as long lifetimes of the 2D quantum gas. We are able to directly detect phase fluctuations and vortices. The setup is especially suitable for many body quantum simulations and applications such as high precision measurements close to surfaces. [Preview Abstract] |
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T1.00052: Quantum pumping with ultra-cold atoms Seth Aubin, Kunal K. Das We propose an experimental scheme for implementing quantum pumps with ultra-cold atoms in an atom chip micro-magnetic trap. Quantum pumping has been the subject of considerable research in mesoscopic solid state systems, since it holds the promise of precise and reversible transport at the single electron level without the application of a bias potential. However, despite significant efforts, it has yet to be observed experimentally due to technical complications. A quantum pump can be simulated experimentally with ultra-cold atoms in a micro-magnetic potential consisting of two magnetic traps connected by a narrow quasi one-dimensional magnetic guide. The pumping potential is generated by a time-dependent optical dipole potential from one or more far off-resonance lasers focused onto the magnetic guide. An atomic system also offers the possibility of studying quantum pumping with bosons and fermions, and we present theoretical predictions for both types of atoms. [Preview Abstract] |
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T1.00053: Quantum Phase Transitions with Spin Frustration in a Trapped Ion System Kihwan Kim, Ming-Shien Chang, Simcha Korenblit, Kazi Rajibul Islam, Christopher Monroe We discuss the use of a linear array of trapped ions for quantum simulations of spin chains with long range interactions [1,2]. In particular, we study interesting phase diagrams with only a few ions that involve multiple normal modes of motion and can feature spin frustration. With trapped ions, there is a potential to directly study the entanglement structure in such exotic ground state spin phases. \newline \newline This work is supported by the DARPA OLE Program under ARO contract, IARPA under ARO contract, ~the NSF PIF Program, and the NSF Physics Frontier Center at JQI. \newline \newline [1] D. Porras and J. I. Cirac, PRL \textbf{92}, 207901 (2004); X.-L. Deng, D. Porras, and J. I. Cirac, PRA \textbf{72}, 063407 (2005). \newline [2] A. Friedenauer, H. Schmitz, J. T. Glueckert, D. Porras {\&} T. Schaetz, Nature Physics \textbf{4}, 757 (2008). [Preview Abstract] |
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T1.00054: Quantum control approach to creating and detecting fractional quantum Hall puddles Stefan Baur, Kaden Hazzard, Erich Mueller We theoretically explore a novel approach to generating few-body analogs of bosonic fractional quantum Hall states [1]. We consider an array of identical few-atom clusters (n = 2, 3, 4), each cluster trapped at the node of an optical lattice. By temporally varying the amplitude and phase of the trapping lasers, one can introduce a rotating deformation at each site. This allows for coherently transferring atoms into highly correlated states. We study target state fidelities and experimental signatures by exactly solving the many-body time dependent Schr\"{o}dinger equation within a truncated basis. In addition to bosonic quantum hall states our method provides a path to create fermionic quantum hall states and other exotic states. [1] SKB, KRAH, and EJM, Phys. Rev. A 78, 061608(R) (2008) [Preview Abstract] |
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T1.00055: Simulating Thermopower in Mott-Hubbard Materials Stanimir Kondov, William McGehee, Brian DeMarco We report progress on a new project to simulate and understand thermopower in Mott-Hubbard materials. Ultra-cold $^{40}$K atoms will be confined in an optical lattice. A temperature gradient applied across the lattice will induce mass transport, which can be resolved using time-of-flight imaging and employed to determine the Seebeck coefficient. The impact of Hubbard parameters, disorder, and lattice geometry on thermopower will be investigated. [Preview Abstract] |
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T1.00056: Luttinger liquids in trapped ultracold atomic Fermi gases C.J. Bolech, Paata Kakashvili, Satyan Bhongale, Han Pu Recent success in manipulating ultracold atomic systems allows to probe different strongly correlated regimes in one dimension. Experimentally, 1D tubes are defined by turning on a 2D optical lattice. Regimes such as the spin-coherent Luttinger liquid and the spin-incoherent Luttinger liquid can be realized by tuning the repulsive inter-atomic interaction strength and trap parameters. Due to the trap potential the density decreases near the edges of the tubes and the spin-incoherent regime is inevitably realized. In general, the spin-coherent Luttinger liquid regime in the center of the tube crosses over to its spin-incoherent counterpart at the edges. We identify the noise correlations of density fluctuations as a robust observable (uniquely suited in the context of trapped atomic gases) to discriminate between these two regimes. On the other hand, the inter-atomic interaction can also be made attractive in order to access Luttinger states that support paired-state ground states that are robust against population imbalance (FFLO-like states) and do not phase separate in the trap as in the case of three dimensional clouds. We explore the finite temperature properties of the attractive regime using the tools of integrability. Finally, we address the concrete prospects of realizing and probing these phenomena experimentally using optical lattices. [Preview Abstract] |
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T1.00057: QUANTUM INFORMATION |
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T1.00058: Scalable Quantum Computation using Two Atomic Species in Independent Optical Lattices Arjun Sharma, Kara Lamb, Peter Scherpelz, Andreas Klinger, Skyler Degenkolb, Kathy-Anne Brickman, Nathan Gemelke, Cheng Chin We confine bosonic $^{133}$Cs and fermionic $^{6}$Li atoms in a dipole trap to evaporatively cool and study the interspecies collision properties as a first step toward quantum information processing. Ultimately, each species will be confined by an independent optical lattice. Cooling the Li atoms into a degenerate band-insulator will allow uniform loading of 1atom/site. These Li atoms will act as quantum bits (qubits). Cs atoms will have a lower filling ratio of 1atom/100sites and will act as messengers to carry entanglement among the qubits. We present a novel technique to create commensurate lattices at 680nm for Li and 1064nm for Cs. One laser beam at each color is split into multiple beams by a diffractive optical element and recombined at the atoms to create independent triangular optical lattices. By relatively translating the two lattices using electro-optic modulators, the Cs messenger atoms can be translated to any Li qubit to perform entangling operations. [Preview Abstract] |
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T1.00059: Quantum Information Processing with Atoms in Arrays of Dipole Potentials Malte Schlosser, Jens Kruse, Christian Gierl, Christoph Ewen, Peter Schauss, Gerhard Birkl Quantum information processing with neutral atoms represents an important experimental approach complementing systems based on trapped ions. By using ultra-cold atoms in two-dimensional dipole trap arrays, one can realize highly controllable and scalable systems with long coherence times. In our experiment, we use sets of optical micro-potentials created by micro-fabricated lens arrays as the architecture for a scalable quantum processor. Due to the large lateral separation of neighboring potential wells, each trap is individually addressable. For flexible architectures, we implement a liquid crystal display in front of a microlens array as a pixel-addressable intensity modulator. By this we are able to control each potential well separately and produce arbitrary trap configurations. We demonstrate the flexible site-specific initialization and coherent manipulation of separated small ensembles of $^{85}$Rb atoms in two-dimensional trap arrays by applying coherent Raman coupling between hyperfine ground states, representing the qubit states. Advanced schemes for scalable atom observation allow us to detect single atoms in two-dimensional sets of dipole traps with high efficiency and reliability. [Preview Abstract] |
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T1.00060: Pulse sequences for dynamical decoupling in an optical lattice broadened by temporal frequency drift Christopher R. Paul, Chao Zhuang, Luciano S. Cruz, Samansa Maneshi, Aephraim M. Steinberg Despite the very long internal coherence time, transverse drift through an inhomogeneously broadened lattice leads to a rapid decay of a pulse-echo signal. We use higher-order echoes, or dynamical decoupling, to probe and subsequently eliminate the effects of this drift. We study the optimal structure of these pulse sequences for simultaneously canceling out different orders of the effect. [Preview Abstract] |
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T1.00061: Simulation of Quantum Operations in a Three-Level System Jason Lee, Mahmoud Lababidi, Mingzhen Tian Lambda-type three-level systems have been studied as potential qubits for quantum computation and quantum memory. Quantum state manipulation through optically controlled quantum operation plays an important role in these settings. In order to understand the physical processes involved and to analyze the state and operation fidelity we developed a theoretical model based on semi-classical theory, which describes the state evolution of the three-level atom driven by the laser pulses. We investigated the fidelity of the quantum operations, which is controlled by laser and atomic parameters in the process, including atomic coherence time, initial state, frequency detuning, amplitude, and phase of the laser control pulses. The simulation encompasses realistic parameters to gauge optimal operation conditions, by optimizing parameters of the laser and atom. We will present the simulation results in comparison to the experiment data. The theoretical model can also be applied to a broader range of processes in three-level systems. [Preview Abstract] |
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T1.00062: Production of Atomic Number States: a Bethe Ansatz Analysis Shou-Pu Wan, Mark Raizen, Qian Niu We analyze the conditions for producing atomic number states in a one-dimensional optical box by the method of laser culling. We solve the problem using the Bethe Ansatz, and justify the use of that method for the present problem. Our approach provides a general theoretical framework that spans a wide range of interaction strength. The limit of strong interactions, so-called Tonks-Girardeau regime, is equivalent to non-interacting fermions. We discuss the relative merits of laser culling of fermions as compared with bosons in terms of possible experimental realization as well as projected fidelity. [Preview Abstract] |
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T1.00063: Optimization of Dynamical Decoupling Using Measurement Feedback Hermann Uys, Michael Biercuk, Aaron VanDevender, Nobuyasu Shiga, Wayne Itano, John Bollinger We study the optimization of dynamical decoupling sequences using $^9$Be$^+$ ions in a Penning ion trap. We artificially synthesize the noise environment the ions see to emulate a variety of physical systems. By incorporating measurement feedback with a Nelder-Mead search algorithm, our locally optimized dynamical decoupling sequences (LODD) attain an order of magnitude improved error suppression compared to known sequences in noise environments with power spectra that have sharp, high-frequency cutoffs. The technique requires no prior knowledge of the noise spectrum. This work shows that optimized dynamical decoupling will be a useful tool in suppressing qubit errors below the fault-tolerant threshold for quantum computation. [Preview Abstract] |
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T1.00064: Fidelity Comparison of Geometric Rotation and Dynamic Rotation Mahmoud Lababidi, Jason Lee, Mingzhen Tian In a two-dimensional Hilbert space,the qubit state can be controlled in the Bloch sphere by rotating the Bloch vector about two perpendicular axes of the Bloch sphere. In a two-level atomic system, these basic rotations can be performed through laser-driven quantum state evolutions, which can be dynamic or geometric. Dynamic rotations are usually realized by control Hamiltonians made of a simple laser pulse driving the quantum system through dynamic evolution. Geometric rotations based on the quantum geometric phase are usually designed using multiple pulse sequences. They rely on the global geometry of the evolution which are immune from certain types of local disturbances on the driving Hamiltonian caused by phase and amplitude noise on the control laser pulse. Through theoretical analysis we compare the dynamic rotation fidelity and geometric rotation fidelity. We optimize the parameters of each rotation, to determine the range of high-fidelity in each type of the geometric rotation. [Preview Abstract] |
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T1.00065: Interaction- and Measurement-Free Quantum Zeno Gates for Single-Atom and Single-Photon Qubits Yuping Huang, Michael Moore By extending the Elitzur Vaidman concept of interaction-free imaging to the few-atom level, we show that on-demand interaction- and measurement-free quantum logic gates can be realized for both single-atom and single-photon qubits [1]. We present a general theory of quantum Zeno phase gates, and describe physical implementations of several useful quantum gates for universal quantum information processing with individual atomic and photonic qubits in a high-Q ring cavity. [1] Y. P. Huang and M. G. Moore, Phys. Rev. A 77, 062332 (2008). [Preview Abstract] |
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T1.00066: LOW TEMPERATURE PLASMAS |
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T1.00067: Calculations and measurements of laser-induced fluorescence in ultracold neutral plasma Scott Bergeson, Francis Robicheaux We compare calculations of laser-induced fluorescence from ultracold plasmas with recent measurements. The calculations are made by integrating the optical Bloch equations for moving ions and following the excited state population as a function of time. In both the calculations and the measurements we clearly see initial rotation of the Bloch vector, disorder induced heating, and plasma expansion. The time at which disorder induced heating is overwhelmed by plasma expansion is studied as a function of initial electron temperature and plasma density. This should provide a measure of electron shielding, including recombination and rescattering effects, in these systems. [Preview Abstract] |
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T1.00068: Ultracold Plasma Expansion Dynamics in High Magnetic Field Kevin Twedt, Xianli Zhang, Steven Rolston We study the expansion dynamics of an ultracold plasma in uniform magnetic fields up to 500 G. We use a time-of-flight projection imaging method to extract the ion distribution at varying times during the plasma evolution. Our previous study showed the transverse expansion velocity in a uniform longitudinal magnetic field scales as B$^{-1/2}$ for fields up to 70 G, explained by a nonlinear ambipolar diffusion model that involves anisotropic diffusion in two directions. Preliminary results show above 100 G and up to 500 G, the expansion velocity does not continue to decrease, but levels off at $\sim $10m/s. This limit corresponds to the ion thermal velocity at an ion temperature of 1 K. We also observe a flat top in the ion images that we attribute to the formation of a shockwave at the edge of the ion cloud during the time of flight to the detector. This work is a preliminary step in pursuing 3D magnetic confinement of the ultracold plasma. This work is partially supported by the NSF. [Preview Abstract] |
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T1.00069: Rydberg three-body recombination experiments in a Penning trap Eric Paradis, Cornelius Hempel, Mallory Traxler, Georg Raithel In this poster, we present work towards observing three-body recombination in a Penning trap (B $\sim$ 3 T). Recombination is an important mechanism in anti-hydrogen formation. The rate of recombination of Rydberg atoms is strongly dependent on the electron temperature ($\sim n_e^2 T^{-9/2}$), and has been numerically calculated for various magnetic fields and electron energies [1]. In our experiment, Rubidium atoms are ionized at the center of the trap, using a narrow-band ($<\sim 5$MHz linewidth) cw excitation laser. Due to the long lifetime of the Penning trap ($\tau \sim 100$s), electron accumulation leads to a high electron density, and cyclotron cooling to a low electron temperature (close to the 4 K background temperature). A field ionization ramp is applied to analyze the state distribution of Rydberg atoms formed in the ion-electron plasma. \textbf{[1]} ``Three-body recombination for protons moving in a strong magnetic field,'' F. Robicheaux and James D. Hanson, Phys. Rev. A {\bf 69}, 010701 (2004). [Preview Abstract] |
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T1.00070: Superradiance and superradiance cascade in a cold Rydberg gas Jianing Han, Haruka Maeda, Tom Gallagher We report the observation of superradiance in a cold $^{85}Rb$ Rydberg gas. Specifically, the superradiant decay from the ns state to the (n-1)p state and from the nd to the (n-2)f state are studied. The observed signal is characterized by the amount of superradiance decay as a function of the total number of atoms, the delay and the electric field dependence. Compare with the superradiance in a room temperature Rydberg gas, two new features are observed in a cold Rydberg gas. First, the superradiance signal decays very fast, the lifetime of the 21f state decayed from the 23d state is 4us at density: $1.5X10^9 cm^{-3}$. Second, the $5p_{3/2}$ state to the nf state transition happens at high density with the assistance of one superradiance photon. These new features lead to more interesting phenomena in a cold Rydberg gas, such as plasma. Moreover, the van der Waals interaction effect and the stark effect induced by free ions will be discussed. Furthermore, superradiance cascade will be presented. Another aspect of this study is that a threshold behavior in a cold plasma formation process suggests the existence of a coherent process. However, little research focuses on this phenomenon. The purpose of this paper is to show that superradiant decay is responsible for this threshold behavior and suprerradiant cascade decay and subsequent multibody collisions lead to the fast plasma formation process. [Preview Abstract] |
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T1.00071: Temporal relaxation of the electron transport properties in magnetized plasma discharges Sasa Dujko, Ronald White, Zoran Petrovic The progress and further improvements of modern technology associated with the non-equilibrium magnetized plasma discharges require the most accurate modeling of charged particle transport under the influence of electric (E) and magnetic (B) fields in neutral gases. In this work, the temporal relaxation of electrons in gases under the influence of dc E and B fields crossed at arbitrary angle is studied via a multi term solution of the Boltzmann equation and Monte Carlo simulation technique. We systematically investigate the explicit effects associated with the E and B fields and field orientations. In particular, we highlight the explicit modification of transport coefficients about by non-conservative collisional processes of attachment and ionization. Among many interesting kinetic phenomena observed for the first time in this work, we note the existence of the transiently negative diffusivity. We systematically study the origin and mechanisms for such phenomena, their sometimes paradoxical manifestation and possible physical implications which arise from their explicit inclusion into plasma models. [Preview Abstract] |
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T1.00072: NEW THEORETICAL METHODS |
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T1.00073: Electron transport dynamics of molecular devices: A time-dependent density functional theoretical study in momentum space Zhongyuan Zhou, Shih-I Chu We propose a first-principles time-dependent density functional theoretical (TDDFT) approach in momentum (P) space for the quantitative study of electron transport dynamics in molecular devices. This approach is free of self-energy function and memory term and beyond the wide-band limit (WBL). It is computationally considerably more efficient than the conventional TDDFT approach in spatial coordinate (R) space. In this approach, the basic equation of motion is a time-dependent integro-differential equation obtained by Fourier transform of the R-space time-dependent Kohn-Sham (TDKS) equation. It is formally exact and includes all the effects and information of the electron transport in the molecular devices. The electron wavefunction is calculated by solving this equation in a finite P-space volume. This approach has been used to calculate the currents through several one-dimensional systems. The results are in very good agreement with those obtained from other theoretical methods, demonstrating the efficiency and power of this approach. [Preview Abstract] |
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T1.00074: An Alternative Approach to Aharonov-Anandan Phase Pierre-Louis Giscard We derive new expressions for the Aharonov-Anandan phase (AA-phase) for time independent Hamiltonians from which we develop a new method for the calculation of the AA-phase. We compare the generic method used to calculate the AA-phase with the method proposed here through four examples; a spin-1/2 particle in a constant magnetic field, an arbitrary infinite-sized Hamiltonian with two known eigenvalues, a Fabry-Perot cavity with one movable mirror and a three mirrors cavity with a slightly transmissive movable middle mirror. We then derive a continuous spectrum operator with the geometric Berry's phase, the Aharonov-Anandan phase or the Samuel-Bhandari phase as expectation value, depending on the conditions in which it is explicitly calculated. [Preview Abstract] |
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T1.00075: Weizsacker energy of unitary Fermi gas in a harmonic trap Alexander Zubarev The universal method of construction of the rigorous lower bounds to the Weizsacker energy is presented. We study a few-fermion system at the unitarity. Upper and lower bounds to the density functional theory (DFT) ground state energy within the local density approximation (LDA) are given. The rigorous lower bounds to the accuracy of the method are derived. [Preview Abstract] |
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T1.00076: Gaussian Techniques applied to Completeness in Optical Calculations Richard Kriske An interesting interpretation of Completeness and Group Theory can be found in using classical Gaussian Calculations that have been used previously in Mapping (from Gauss and Riemann) and Relativity. A simple reinterpretation of the observer and the meaning of the completeness of the observation yields some fascinating results that may have a Theoretical Significance and seems to yield some testable Optical and Atomic Effects. The most interesting part of this interpretation is that it is not a difficult deviation from the current theory. [Preview Abstract] |
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T1.00077: Strength of electromagnetic, acoustic and Schr\"{o}dinger reflections Sergiy Mokhov, Boris Zeldovich The notion of reflection strength $S$ of a plane wave by an arbitrary non-absorbing layer is introduced, so that the intensity of reflection is $R$=tanh$^{2}S$. We have shown that the total strength of reflection by a sequence of elements is expressed through particular element strengths and mutual phases between them by a simple addition rule; in particular, its possible maximum is the sum of the absolute strengths of constituents. We show that the standard Fresnel reflection may be understood in terms of variable $S$ as a sum or difference of two separate contributions, due to an impedance step and a speed step. Strength of reflection for propagating acoustic and quantum mechanical waves is also discussed. The one-dimensional wave equation describing propagation and reflection of waves in a layered medium is transformed into an exact first-order system for the amplitudes of coupled counter-propagating waves. Any choice of such amplitudes, out of continuous multitude of them, allows one to get an accurate numerical solution of the reflection problem. We discuss relative advantages of particular choices of amplitude. [Preview Abstract] |
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T1.00078: Displacement formulas for noncommutative operators Jean-Francois Van Huele, Bailey Hsu The study of the time evolution of quantum systems leads us to the manipulation of exponentials of noncommuting observables. We present analytical expressions for displacements that involve noncommutative operators. We consider successively operators from noncommutative quantum mechanics, radial momentum operators, and spin-dependent displacement operators. The noncommutativity results in the appearance of phase factors and of staggered displacements. To obtain these results we apply Baker-Campbell-Hausdorff-like formulas. The displacement formulas can be used to construct propagators of spin and other noncommuting quantum systems. [Preview Abstract] |
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T1.00079: Analytic propagators for systems with spin-orbit-type interactions Bailey Hsu, Jean-Francois Van Huele We discuss propagators in spin-orbit-type systems. In addition to the kinetic energy, these systems exhibit potentials that mix position, momentum and spin operators. We give analytic expressions for propagators for constrained spin-orbit coupling Hamiltonians $H=\frac{\textbf{p}^2}{2m}+f(\textbf{x},\textbf{p},\sigma)+\frac{1}{2}m\eta^2 (x^2+y^2)$ for some specific functions $f$. We discuss the applicability of two propagator construction methods and we obtain the evolution of particles with spin. [Preview Abstract] |
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T1.00080: A General, Simple, Blackbox Algorithm for the Evaluation of the Exponential of a Matrix Charles Weatherford, Daniel Gebremedhin, Xingjun Zhang The evaluation of a matrix exponential function is a classic problem of computational linear algebra. Many different methods have been employed for its numerical evaluation [Moler C and van Loan C 1978 {\it SIAM Review}{\bf \ 20} 4], none of which produce a definitive algorithm which is broadly applicable and sufficiently accurate, as well as being reasonably fast. Herein, we employ a method which evaulates a matrix exponential as the solution to a first-order initial value problem in a pseudo-time variable. The new aspect of the present implementation of this method is to use finite elements in the pseudo-time variable. [Weatherford C A, Red E, and Wynn A 2002 {\it Journal of Molecular Structure}{\bf \ 592} 47] Then using an expansion in a properly chosen pseudo-time basis, we are able to make accurate calculations of the exponential of any given matrix as the solution to a set of simultaneous equations, even when the matrix is singular or rectangular. [Preview Abstract] |
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T1.00081: Kaluza-Klein-Carmeli Metric from Quaternion-Clifford Space, Lorentz' Force, and Some Observables Vic Christianto, Florentin Smarandache It was known for quite long time that a quaternion space can be generalized to a Clifford space, and vice versa; but how to find its neat link with more convenient metric form in the General Relativity theory, has not been explored extensively. We begin with a representation of group with non-zero quaternions to derive closed FLRW metric, and from there obtains Carmeli metric, which can be extended further to become 5D and 6D metric (which we propose to call Kaluza-Klein-Carmeli metric). Thereafter we discuss some plausible implications of this metric, beyond describing a galaxy's spiraling motion and redshift data as these have been done by Carmeli and Hartnett. In subsequent section we explain Podkletnov's rotating disc experiment. We also note possible implications to quantum gravity. Further observations are of course recommended in order to refute or verify this proposition. [Preview Abstract] |
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T1.00082: QUANTUM AND/OR NONLINEAR OPTICS |
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T1.00083: Quantum transport in a nonlinear optical fiber: single-photon switching, photonic bound states and more Mohammad Hafezi, Darrick E. Chang, Vladimir Gritsev, Eugene Demler, Mikhail D. Lukin We examine the quantum transport properties of a few photons inside a one-dimensional nonlinear waveguide when the evolution is determined by the quantum nonlinear Schrodinger equation. The tight transverse confinement of the photonic modes enables a large atom-field coupling strength. Therefore, by coupling light to atoms loaded in a fiber, such a system is capable of acting as a single-photon switch, where the transmission of single photons occurs with high probability while that of multiple photons is strongly suppressed. This switching behavior also manifests itself in higher-order correlation functions of the transmitted field. In particular, when the interaction between photons is effectively repulsive, the suppression of multi-photon components results in anti-bunching of the transmitted field. In the attractive case, the switch can exhibit both anti-bunching and bunching behaviors. We show that the bunching is due to the resonant excitation of bound states of photons by the input field. Finally, an experimental implementation of such a system in hollow-core fibers loaded with cold atoms is discussed. [Preview Abstract] |
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T1.00084: Use of buffer gas to reduce the decoherence of Rb atoms in hollow-core photonic bandgap fibers Amar Bhagwat, Aaron Slepkov, Vivek Venkataraman, Pablo Londero, Alexander Gaeta Rapid advances have been made recently in the generation and use of Rb vapor inside hollow-core photonic bandgap fibers (HCPBF) for performing low-light-level nonlinear optics. Using light-induced atomic desorption, we generate significant Rb-vapor densities inside the HCPBF. The strong decoherence associated with collisions of the atoms with the core walls and the large transit-time broadening represent major challenges for applications based on sensitive quantum optical phenomena. Introduction of buffer gases impedes the motion of Rb atoms across the beam resulting in a decreased rate of collisions with the walls and a reduction in transit-time broadening. We investigate the effects of Ne on the desorbed Rb atoms and demonstrate enhanced optical pumping between the Rb-87 ground states in the presence of the buffer gas. [Preview Abstract] |
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T1.00085: Efficient single photon detection with cold atoms in hollow fiber Sebastian Hofferberth, Michal Bajcsy, Thibault Peyronel, Mohammad Hafezi, Vlatko Balic, Alexander S. Zibrov, Vladan Vuletic, Mikhail Lukin Cold atoms confined inside a hollow core photonic crystal fiber are a promising medium for studying nonlinear optical interactions at extremely low light levels. For instance, we demonstrated in recent experiments how such an atomic ensemble consisting of $\sim10^3$ laser cooled $^{87}Rb$ atoms results in an optically dense medium whose transparency can be controlled with pulses containing just a few hundred photons [1]. Here, we describe how this medium can be used for high efficiency detection of single stored excitations. This in turn allows for non-destructive detection of single photons with near unity probability, which for example could greatly enhance the efficiency of the DLCZ-scheme for quantum repeaters. We also discuss recent improvements of the atom loading scheme to increase the optical depth of the atomic medium inside the hollow core fiber. [1] M.~Bajcsy, S.~Hofferberth, V.~Balic, T.~Peyronel, M.~Hafezi, A.~S.~Zibrov, V.~Vuletic, M.~D.~Lukin, Efficient all-optical switching using slow light within a hollow fiber, arXiv:0901.0336 (2009) [Preview Abstract] |
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T1.00086: Refractive Index Enhancement in an Atomic Vapor Nicholas Proite, J.P. Sheehan, Jonathan Green, Brett Unks, Deniz Yavuz We experimentally demonstrate a scheme where a laser beam experiences an index of refraction of 10$^{-5}$ with vanishing absorption in an atomic medium [1]. The essential idea is to excite two Raman resonances with appropriately chosen strong control lasers in a far-off resonant atomic system. We observe this effect by utilizing the hyperfine ground states of $^{85} $Rb and $^{87}$Rb simultaneously in a thin vapor cell heated to 150$^{\circ}$C. [1] N.~A.~Proite, \textit{et.~al.}, Phys.~Rev.~Lett.~\textbf{101}, 147401 (2008). [Preview Abstract] |
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T1.00087: Gauge potentials and relativistic effects for stationary-light polaritons Johannes Otterbach, Razmik Unanyan, Julius Ruseckas, Gediminas Juzeliunas, Michael Fleischhauer We discuss dynamic phenomena of light-matter quasi particles arising in the Raman interaction of a weak light field with a coherently driven atomic ensemble. These so called dark-state polaritons (DSP) posses an externally controllable mass and are the basis of phenomena such as slow and stationary light. First we discuss the case of stationary light at very short length scales. The dynamics is then governed by an effective Dirac equation. This behavior sets the limit for the compression of stationary light in such setups. We discuss relativistic effects, as e.g. Klein tunneling and Zitterbewegung, that can be observed in the system at hand. Second we present a setup to create effective magnetic fields for DSPs. At large pulse lengths DSPs behave as Schr\"odinger particles and a confinement to lower dimensions is easily done. These effective fields can be used to study a variety of single- and many-particle effects as e.g. Lorentz forces for neutral particles and the fractional quantum Hall effect (FQHE). [Preview Abstract] |
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T1.00088: Photon Detection of Single Atoms in an Optical Cavity with Faraday Rotation David Norris, Eric Cahoon, Luis Orozco We demonstrate a technique for rapid detection of freely-moving atoms in a Fabry-Perot cavity. We drive the cavity on-axis with linearly polarized light resonant with the D2 line in Rb 85. A cold beam of atoms from a modified magneto-optical trap intersects the cavity mode, where the atoms scatter light into the orthogonally polarized mode. We enhance the process with Faraday rotation in an applied magnetic field. Avalanche photodiodes record photon emissions from the orthogonal mode, with multiple emissions in a short time window the signature of a transiting atom. We characterize the efficiency of the detection process through a statistical analysis of the recorded photon series. We show successful detection of single atoms in 1 microsecond with greater than 99.8{\%} confidence. Work supported by NSF. [Preview Abstract] |
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T1.00089: Photon diode: performing nonunitary operations on quantum light Gor Nikoghosyan, Michael Fleischhauer We discuss the interaction of two quantized modes of light with a spectrally broadened atomic ensemble. We show that the system is analogous to a two level system interacting with a bosonic reservoir, where the photonic modes correspond to the atomic states and the atomic ensemble corresponds to the modes of the reservoir. In contrast to the photonic reservoirs, the atomic ensembles can be easily controlled which can be used to simulate the dynamics of an open two level system in a reservoir with tunable spectrum. Due to the coupling with the atoms the analog of spontaneous decay for photons is obtained. This process leads to an irreversible transfer of photons from one mode to the other. The effect can be used for large variety of applications; e.g. the creation of new quantum states, the transfer of photons of optical frequency to microwave domain and vice versa, or the construction of a diode for photons, i.e. a device where single photon pulses injected in any of the two input ports will be directed to the same output port. [Preview Abstract] |
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T1.00090: Intensity auto- and cross-correlations for a driven two-mode cavity coupled to a three-level atom Patrick Hemphill, James Clemens We calculate two-time intensity auto- and cross-correlations for light transmitted through a weakly driven optical cavity with two degenerate modes of orthogonal linear polarization coupled to a single three-level atom in the $\Lambda$ configuration. We compare the resulting autocorrelations with the two-level atom coupled to a single optical cavity mode and identify a transition from photon bunching to photon antibunching as a function of the coupling to the third atomic level. [Preview Abstract] |
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T1.00091: Atomic quantum superposition state generation via optical probing Anne E. B. Nielsen, Uffe V. Poulsen, Antonio Negretti, Klaus M{\O}lmer Light is a useful tool to probe the state of matter. Performing measurements on a light field, which has interacted with a system, changes the density operator of the system, and this back action has, e.g., been utilized to spin squeeze atoms. Here, we demonstrate that a similar measurement scheme allows preparation of N spin-1/2 atoms in a superposition of a state with most of the atoms in the spin up state and a state with most of the atoms in the spin down state [1]. The protocol exploits the strong coupling regime of cavity QED, achieved experimentally in [2], to reduce the decoherence effects of light field losses, and we use the stochastic master equation derived in [3] to analyze the performance of the setup. In addition to a continuous coherent state probe, we also investigate probing with a continuous beam of squeezed light. Probing with a slightly squeezed vacuum can improve the protocol. [1] A. E. B. Nielsen et al, arXiv:0812.4048. [2] F. Brennecke et al, Nature {\bf450}, 268 (2007); Y. Colombe et al, Nature {\bf450}, 272 (2007). [3] A. E. B. Nielsen et al, Phys. Rev. A {\bf77}, 052111 (2008). [Preview Abstract] |
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T1.00092: An Ultra-Bright Omnidirectional Atomic-Vapor Photon-Pair Source Based on Doppler-Free Four-Wave-Mixing and Collective Emission Yuping Huang, Michael Moore Four-Wave Mixing (FWM) in atomic vapors has become competitive with solid-state down-conversion as a source of entangled photon pairs. FWM schemes rely on collective enhancement to generate strong pair correlation. In general, collective enhancement is only achieved in a very narrow emission solid-angle, restricting the obtainable beam brightness of photon pairs. To substantially increase the pair production rate, we propose a novel `butterfly' level scheme for omnidirectional photon pair generation. With multi-photon Doppler-free pumping, background Rayleigh scattering is dipole-forbidden, and collective emission is permitted in all directions. A pair production rate of $10^{12}$ per second should be obtainable with an ensemble of only $\sim 10^6$ atoms. Individual pairs also exhibit near-maximum polarization entanglement over a wide solid-angle. In addition, suppressed Rayleigh scattering significantly reduces recoil-induced heating, which enables the use of atomic samples ranging from hot vapors to Bose-Einstein condensates. [Preview Abstract] |
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T1.00093: ATOMS IN OPTICAL LATTICES |
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T1.00094: Progress Towards Single-site Imaging of Fermions in an Optical Lattice Dylan Jervis, David McKay, Michael Yee, Julie Sutton, Jason McKeever, Alan Stummer, Joseph Thywissen We discuss progress towards $\emph{in-situ}$ imaging of a single plane of fermionic $^{40}$K atoms in an optical lattice. Spin-sensitive $\emph{in-situ}$ imaging will allow for local measurements of occupation, spin ordering, and domain structure of interesting many-body phases, including band insulators, Mott insulators, N\'{e}el antiferromagnets, superfluid states, and striped or other structured ordering. We are currently testing a design that collects light from the 405 nm $\mathit{4S}\rightarrow\mathit{5P}$ transition of $^{40}$K through a thin (200 micron) vacuum window in order to achieve a resolution of better than 700 nm. We have measured the optical transfer function of this system in air by imaging a test target with features as small as 50 nm and determined our resolution to be better than 500nm. We also present our work on locking to the $\mathit{4S}\rightarrow\mathit{5P}$ transition using saturation spectroscopy. [Preview Abstract] |
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T1.00095: Towards single site addressability in optical lattices Manuel Endres, Christof Weitenberg, Jacob Sherson, Immanuel Bloch, Stefan Kuhr Investigations of ultracold quantum gases in optical lattices are mostly restricted to access global information of the system. By contrasts we are developing experimental techniques revealing the local distribution of the trapped gas. Main part of the experiment will be an optical imagine system with a spatial resolution better than the lattice spacing of a near infrared optical lattice. In addition the setup will allow for manipulation of the atoms on a local scale. Collecting the fluorescence light of the trapped atoms, will enable us to observe the local dynamics of the many-body system. With an additional strongly focused laser beam single sites of the optical lattice can be addressed. Possible applications of single site addressability are e.g. single q- bit rotations via local rf-resonance or disturbance of the many- body system on a local scale. In principle the experimental setup will open new possibilities for the investigation and manipulation of strongly correlated atomic systems for the purpose of quantum simulation and quantum information processing. [Preview Abstract] |
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T1.00096: Polarization-dependent atomic dipole traps behind a pinhole for controllable manipulation of qubit locations in a quantum memory Katharina Gillen-Christandl, Bert Copsey, Glen Gillen We present computational results for the polarization-dependent trapping potentials of atom traps behind a pinhole that are suitable for a quantum memory. We previously calculated the trapping properties of localized bright and dark spots formed directly behind a pinhole for a laser beam at normal incidence [1]. In our recent computational research we found that the traps remain intact upon tilting the laser beam. Exploiting the polarization-dependence of atomic dipole traps [2], we have explored the use of tilted, circularly polarized laser beams to store Rb atoms in specific magnetic substates. We found that two laser beams of opposite circular polarization incident on a pinhole at an angle allow the storage of two atoms in two different magnetic substates in two separate locations. Further, our results show that physically tilting the laser beams allows us to bring the two atoms together and apart controllably. In this fashion, we hope to use an array of pinholes as a quantum memory with the ability of bringing pairs of qubits together and apart for 2-qubit quantum operations. [1] G. D. Gillen, et al., Phys. Rev. A 73 (2006), 013409, [2] I. Deutsch, et al., Phys. Rev. A, 57 (3), 1972-1986 (1998). [Preview Abstract] |
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T1.00097: The Quantum Gas Microscope Jonathon Gillen, Waseem Bakr, Amy Peng, Simon F\"olling, Markus Greiner Ultracold quantum gases are seen as models for studying questions of modern condensed matter physics because they provide a clean way of implementing fundamental Hamiltonians for complex many-body physics. In addition, they also provide novel ways of preparing the ensemble and of extracting information about the resulting many-body state from the system. We present an experiment to realize a 2D quantum gas with very high aspect ratio close to a dielectric surface as well as a 2D optical lattice geometry. The gas is positioned at the focus of a high numerical aperture optical microscope, providing a way for high resolution preparation, manipulation and analysis of the ensemble. Our novel trapping techniques allow us to generate a smooth trap and long trapping life times despite the vicinity of the substrate. [Preview Abstract] |
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T1.00098: Experimental Probe of Antiferromagnetic Ordering of $^6$Li in an Optical Lattice J.H. Hitchcock, P.M. Duarte, T.A. Corcovilos, R.G. Hulet We have developed an apparatus to probe magnetic ordering in $^6$Li using a spin mixture of magnetic sub-levels from the lowest hyperfine state. The degenerate Fermi gas is prepared all optically by loading and evaporative cooling in a high-power optical trap. Our primary goal is the observation of antiferromagnetic (AFM) ordering predicted for an equal spin mixture in a three dimensional lattice with one fermion per site. To identify the AFM phase we will use a near resonant laser to Bragg scatter from the (${\scriptstyle{^1\!/_2}\,{^1\!/_2}\,{^1\!/_2}}$) lattice plane. A robust control system has been established to vary parameters such as spin polarization, atomic interaction, and lattice depth to extend this system in the future to different lattice geometries. [Preview Abstract] |
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T1.00099: Probing Nagaoka ferromagnetism in optical superlattices Javier von Stecher, Eugene Demler, Mikahil Lukin , Ana Maria Rey In 1966, Nagaoka predicted that interaction-induced ferromagnetism occurs in lattices with specific geometry when there is one fewer electron than in the half-filled system (one hole). Here, we~describe a controllable method for observing Nagaoka Ferromagnetism (NF) in cold atoms by loading them in optical superlattices. First, we discuss how to probe NF in an array of isolated plaquettes (four lattice sites arranged in a square). Next, we discuss the more generic case of an array of weakly coupled plaquettes and suggest a method for creating and detecting long range ferromagnetic correlations. [Preview Abstract] |
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T1.00100: Effects of interaction on the localization of ultracold atoms in 1D quasi-periodic potentials Franco Dalfovo, Marco Larcher, Michele Modugno We study the time evolution of an atomic wave-packet in a one-dimensional sinusoidal quasi-periodic potential by numerically solving a discrete Gross-Pitaevskii equation. The results are compared with those obtained for the Anderson localization of noninteracting particles. For the shape of the initial wave-packet we use both a wavefunction completely localized in a single lattice site and a broader wavefunction having Gaussian envelope. In both cases, there are evidences of a destruction of the localization by the interaction between atoms. In particular, a repulsive interaction causes a broadening of the crossover between extended and exponentially localized states and an upward shift of the strength of the disorder needed to localize the atoms. We discuss also the connections between our results and current experiments with ultracold atoms in bichromatic lattices. [Preview Abstract] |
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T1.00101: Self-trapped dynamics in 2D optical lattice Shuming Li, Rafael Hipolito, Jean-Felix Riou, David Weiss, Anatoli Polkovnikov, Ana Rey We will discuss a mean field model to study the expansion of an array of one dimensional vertical tubes of cold bosonic atoms confined in a two dimensional optical lattice after the crossed dipole trap used for the initial loading is suddenly turned off. The method uses a Lagrangian formalism to derive Newtonian-like equations of motion that include tunneling between wells and nonlinear mean field effects due to atomic interactions. In our model, the pure mean field dynamics predicts macroscopic self-trapping manifested in accumulation of atoms at the edge of the cloud and formation of a hole at the center. When quantum fluctuations are counted for, the self-trapping is considerably suppressed, and the predictions of the model are in better agreement with the recent experiment measurements. [Preview Abstract] |
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T1.00102: Accounting for on-site correlations with a generalized Bose-Hubbard model Kaden Hazzard, Erich Mueller Near a Feshbach resonance, on-site correlations limit the applicability of the standard Bose-Hubbard model. We present a generalized Bose-Hubbard model which transcends this problem. This model accommodates arbitrary on-site correlations -- even those found in exotic situations, such as when rapid rotation of each site creates an array of coupled fractional quantum Hall puddles. One of the remarkable strengths of our model is that even a mean field approximation includes all on-site correlations. We describe how these on-site correlations modify the phase diagram, deplete the condensate, and even deep in the superfluid give rise to features characteristic of strongly interacting Bose gases. We argue that current attempt to quantitatively describe cold atom emulations of condensed matter models must include these correlations. [Preview Abstract] |
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T1.00103: Implementing the single-species two-component Bose-Hubbard model in an optical lattice Bryce Gadway, Daniel Pertot, Rene Reimann, Bartosz Bogucki, Dominik Schneble The two-component Bose-Hubbard model exhibits interesting quantum phases, and mimics an anisotropic Heisenberg model for quantum magnetism in the limit of weak hopping and unit occupancy. It can be realized by using two different hyperfine states of a single species of ultracold bosonic atoms trapped in a state-dependent optical lattice. For the production of $^{87}$Rb Bose-Einstein condensates we employ a moving-coil transporter apparatus including a TOP trap that serves as a ``funnel'' to load pre-cooled thermal atoms into a crossed optical dipole trap, where the actual condensation takes place. A three-dimensional optical lattice is then superimposed onto the optically trapped BEC. We present our current work regarding the preparation of a clean Mott insulator state, the control of hyperfine states, and the implementation of a state-dependent lattice. [Preview Abstract] |
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T1.00104: Coherent tunneling of atoms and dimers in half spaces Michael Grupp, Reinhold Walser, Wolfgang Schleich Feshbach scattering of fermions in an one-dimensional optical lattice is an intensively investigated subject [1,2]. Scattering theory in free space differs significantly from scattering in a lattice. By breaking the continuous translation symmetry the center-of-mass momentum of the two particles become a new control parameter of Feshbach scattering. We have reported numerical results of this effect in [3]. In the present contribution we study a simple analytic model of this effect by considering the coherent Feshbach scattering of atoms and dimers in half spaces.\newline [1] I.~Bloch, J.~Dalibard, W.~Zwerger, Rev. Mod. Phys. 80, 885 (2008) [2] N.~Nygaard, R.~Piil, K.~M\o lmer, Phys. Rev. A 78, 023617 (2008)\newline [3] M.~Grupp, R.~Walser, W.~Schleich, A.~Muramatsu and M.~Weitz, J. Phys. B: At. Mol. Opt. Phys. 40 (2007) 2703-2718 [Preview Abstract] |
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T1.00105: APPLICATIONS OF AMO SCIENCE |
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T1.00106: Possible Explanation For Multiple Electron Emission From Pyroelectric Crystals In Dilute Gases Stephen Shafroth, David Kaleko, James Brownridge Pyroelectric crystals such as LiNbO3 when cut perpendicular to their z axes and when heated or cooled produce strong electric fields at their surfaces. If a 4 mm dia x 10 mm crystal is immersed in a dilute gas it acts as an accelerator of electrons when the surface is negative and positive ions when the surface is positive. In both cases a focused beam results but in the electron case multiple electron peaks are observed if they are detected through a pin hole with a surface barrier detector(1). In this poster we give evidence for an explanation of this effect. (1) Brownridge, J. D., Shafroth, S. M., Trott, D. W., Stoner, B. R., and Hooke, W. M., Observation of multiple nearly monoenergetic electron production by heated pyroelectric crystals in ambient gas, Appl. Phys. Lett., 78, 1158 (2001) [Preview Abstract] |
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T1.00107: A rare-earth-magnet ion trap for confining low-Z, bare nuclei Samuel M. Brewer, Joseph N. Tan Simplifications in the theory for Rydberg states of hydrogenlike ions allow a substantial improvement in the accuracy of predicted levels, which can yield information on the values of fundamental constants and test theory if they can be compared with precision frequency measurements.[1] We consider the trapping of bare nuclei (fully-stripped) to be used in making Rydberg states of one-electron ions with atomic number 1$<$ Z $<$ 11. Numerical simulation is used here to study ion confinement in a compact, Penning-style ion trap consisting of electrodes integrated with rare-earth permanent magnets, and to model the capture of charge-state-selected ions extracted from an electron beam ion trap (EBIT). An experimental apparatus adapted to the NIST EBIT will also be discussed. Reference: [1] U.D. Jentschura, P.J. Mohr, J.N. Tan, and B.J. Wundt, ``Fundamental constants and tests of theory in Rydberg states of hydrogenlike ions,'' Phys. Rev. Lett. 100, 160404 (2008). [Preview Abstract] |
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T1.00108: High Capacity Hydrogen Absorption in Supported Isolated Molecules and Clusters Bellave Shivaram, Adam Phillips Results of recent experiments at the University of Virginia where isolated molecules and clusters of transition metal based organo metallic complexes collected on quartz substrates have shown record breaking hydrogen gas absorption at room temperature will be presented. Existing theoretical suggestions for the exotic nature of the binding of molecular hydrogen to such complexes will be discussed. [Preview Abstract] |
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T1.00109: Progress toward a Radon EDM Measurement Tim Chupp An EDM is a permanent electric dipole moment of a system, i.e. a separation of charge along the total angular momentum vector. The EDM is a time-reversal-even vector, but the angular momentum is a time-reversal-odd axial vector. Thus a non-zero EDM in a non-degenerate system violates the symmetries of time reversal (T) and parity (P). By application of the CPT theorem, the EDM is CP violating and would arise due to elementary particle interactions among the system's constituents. Searches with atoms, molecules, the neutron and elementary particles continue with the goal of discovering an EDM and clarifying the sources of CP violation. Atoms with octupole deformed nuclei are among the newest systems to be considered because the nuclear deformation gives rise to an enhanced CP violating nuclear charge distribution, the Schiff moment. This talk will describe an experimental program underway at TRIUMF in Vancouver, B.C., to search for the EDM with laser-polarized radioactive radon isotopes, which are expected to have enhancements of several hundred relative to $^{199}$Hg, which has recently improved limits on sources of the Schiff moment and other CP violating phenomena. [Preview Abstract] |
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T1.00110: A large frame gyrolaser Maria Allegrini, Jacopo Belfi, Nicol\`o Beverini, Filippo Bosi, Giorgio Carelli, Angela Di Virgilio, Enrico Maccioni, Fiodor Sorrentino A large frame ring laser gyroscope optimized for very high rotational sensitivity has been designed and built. It can be used for fine control of the interferometer mirrors alignment for the Earth based third generation gravitational antenna. Another foreseen application is geophysical monitoring of the Earth rotational motion. Presently, the ring laser optical cavity is a square with 1.60 m of side with 4 mirrors of reflectivity near 99.999{\%}. The mechanical drawing allows easy scaling of the square area from the present 2m$^{2}$ value down to 0.81 m$^{2}$. Without optimization of the isolation system from the vibration noise of the environment, preliminary recording of the power spectral noise indicates a rotational resolution near to 10$^{8}$ rad/(sHz$^{1/2})$ at 1 Hz. Exploitation for a three dimensional sensor, composed by three ~independent gyroscopes, is in progress. [Preview Abstract] |
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T1.00111: Atomic Magnetometry in the Mesospheric Sodium Layer B. Patton, S. Rochester, J. Higbie, R. Holzl\"{o}hner, D. Bonaccini Calia, D. Budker Within the Earth's mesosphere a band of free sodium atoms exists at altitudes of 90--100 km. This mesospheric sodium layer is the basis for ``laser guide stars'' employed in observational astronomy [1]. We will outline an experiment to use the $^{23}$Na atoms in this layer for high-precision atomic magnetometry; such a measurement would yield geomagnetic data on a previously unexplored length scale. A schematic of the proposed experiment will be presented, as well as some interesting challenges inherent in performing an atomic physics experiment outside the confines of the laboratory.\newline \newline [1] W.~Happer \emph{et al.}, J. Opt Soc. Am. A \textbf{11}, 263 (1994) [Preview Abstract] |
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T1.00112: Prospects for Magnetometry with Mesospheric Sodium James Higbie, Dmitry Budker, Brian Patton, Eric Corsini Atomic sodium in the mesosphere has been studied for a number of years, with particular reference to its use in artificial guide stars for adaptive-optics telescopes. In this work, we present progress toward use of mesospheric sodium for measurement of geomagnetic fields, including detailed simulation results. Such measurements would complement existing satellite magnetometry missions at a small fraction of the cost. Projections of ultimate magnetometric sensitivity will be given, and work toward experimental realization will be discussed. [Preview Abstract] |
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T1.00113: Progress towards magnetometry with nitrogen-vacancy ensembles in diamond Victor Acosta, Erik Bauch, Micah Ledbetter, Dmitry Budker Optical magnetometers based on spin-precession in alkali-vapor cells can measure magnetic felds with great precision and without cryogenics, however spin-altering collisions limit the sensitivity of small sensors [1]. Paramagnetic impurities in diamond, on the other hand, are a promising system for mm- and $\mu $m-scale magnetometers, because diamond has a high Debye temperature (T$_{D}$ =2230 K) and $^{12}$C has zero nuclear spin, which translates into long spin coherence times (approaching 1 ms [2]) at room temperature. Diamond is also optically transparent over a wide range of wavelengths and is chemically inert. Nitrogen-Vacancy (NV) centers have a spin-triplet ground state and convenient optical transitions, allowing for efficient optical pumping and magnetic detection. Recently, single NV-centers were used for nm-scale magnetometry. Here we discuss progress towards the development of a high-density NV-ensemble magnetometer. The spin-projection noise-limited sensitivity is estimated to be at or below the fT\textit{/$\surd $}Hz level for mm-scale devices [3]. [1] D. Budker and M. Romalis, Nat. Phys. \textbf{3}, 227 (2007). [2] T. Gaebel et. al., Nat. Phys. \textbf{2}, 408 (2006). [3] J. M. Taylor et. al., Nat. Phys. \textbf{4}, 810 (2008). [Preview Abstract] |
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T1.00114: Optical magnetometry with sub-wavelength spatial resolution using individual spins in diamond Jeronimo Maze, Peter Maurer, Paul Stanwix, Liang Jiang, Jonathan Hodges, Alexey Gorshkov, Alexander Zibrov, Ronald Walsworth, Mikhail Lukin The ability to map weak magnetic fields with nanometer resolution is of great importance in biological science and high precision metrology of nanoscale structures. We describe and demonstrate a new technique that combines high spatial resolution in the spirit of stimulating-emission-depletion (STED) fluorescence microscopy [1] and nanoscale magnetic sensing with individual spins in diamond [2,3]. This new magnetic sensing and nanometer resolution fluorescence microscopy approach (m-STED) will allow detection of single electronic spins at a distance of 10 nm with 5-7 folds improvement beyond the diffraction limit lateral resolution. \\[4pt] [1] Hell, S. W. and J. Wichmann, Opt. Lett. 19, 780 (1994).\newline [2] J.R. Maze, et al., Nature 455, 644 (2008).\newline [3] J.M. Taylor, et al., Nature Physics 4, 810 (2008). [Preview Abstract] |
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T1.00115: NV diamond magnetometers for bioimaging Paul Stanwix, My Linh Pham, Tsun Yeung, Daniyar Nurgaliev, Paola Capellaro, Ronald Walsworth We are applying NV-diamond magnetometry to new tools for bioimaging: (i) a wide- field-of-view magnetic field imager for mapping neuronal network dynamics; and (ii) diamond nanocrystals for imaging function in living cells. Initial progress will be reported. [Preview Abstract] |
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T1.00116: COLD ATOMS, MOLECULES, AND PLASMAS |
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T1.00117: Deceleration of continuous molecular beams Wade Rellergert, Eric Hudson A method for decelerating a continuous beam of neutral polar molecules is theoretically demonstrated. This method utilizes non-uniform, static electric fields and regions of adiabatic population transfer to generate a mechanical force that opposes the molecular beam's velocity. By coupling this method with irreversible trap-loading, molecular densities $\geq$ 10$^{11}$~cm$^{-3}$ are possible. When used in combination with forced evaporative cooling, the proposed method may represent a viable route to quantum degeneracy for a wide-class of molecular species. [Preview Abstract] |
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T1.00118: Alternating gradient guiding of strong-field seeking polar molecules Thomas Wall, Simon Armitage, Jony Hudson, Ben Sauer, Ed Hinds, Mike Tarbutt Cold molecules are useful in a wide variety of research areas, from tests of fundamental physical theories to applications in chemistry and biology. It is of great value to these experiments to cool and control molecules. Strong-field seeking molecules are attracted to maxima of electric field strength. Static maxima cannot be created in free space, but dynamic control can be achieved with a field that alternates in time. We have built an alternating gradient electric guide and have used it for transporting beams of CaF over a length of 1m. We present data showing how the guiding efficiency depends on the amplitude and switching frequency of the applied field. We compare our results with those obtained from a simple analytical model, and with those from complete numerical simulations of the experiments. [Preview Abstract] |
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T1.00119: Magnetic field modification of ultracold molecule-molecule collisions T.V. Tscherbul, Yu.V. Suleimanov, V. Aquilanti, R.V. Krems We present an accurate quantum mechanical study of elastic scattering and spin relaxation in collisions of O$_2(^3\Sigma_g^-)$ molecules at cold and ultracold temperatures in the presence of a magnetic field. Our calculations show that magnetic spin relaxation in molecule-molecule collisions is extremely efficient except at magnetic fields below 10 G. The magnetic field dependence of elastic and inelastic scattering cross sections at ultracold temperatures is dominated by a manifold of Feshbach resonances with the density of $\sim$100 resonances per Tesla for collisions of molecules in the absolute ground state. This suggests that the scattering length of ultracold molecules in the absolute ground state can be effectively tuned in a very wide range of magnetic fields. Our calculations demonstrate that the number and properties of the magnetic Feshbach resonances are dramatically different for molecules in the absolute ground and excited spin states. [Preview Abstract] |
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T1.00120: Cold collisions of OH($^2\Pi$) molecules with $^3$He atoms in combined electric and magnetic fields T.V. Tscherbul, G.C. Groenenboom, R.V. Krems, A. Dalgarno The realization of a new magneto-electrostatic trap for cold polar molecules suggests new possibilities of using combined electric and magnetic fields to manipulate molecular collisions at low temperatures. We use accurate quantum mechanical calculations to analyze the effects of parallel electric and magnetic fields on collision dynamics of OH molecules. It is demonstrated that spin relaxation in He-OH collisions at temperatures below 0.01 K can be effectively suppressed by moderate electric fields of order 10 kV/cm. We show that electric fields can be used to manipulate Feshbach resonances in collisions of cold molecules. Our theoretical results can be tested in experiments with OH molecules in Stark decelerated molecular beams and magneto-electrostatic traps. [Preview Abstract] |
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T1.00121: Resonance phenomena in ultracold dipole-dipole scattering of bosons and fermions. Vladimir Roudnev, Michael Cavagnero Elastic scattering resonances occurring in ultracold collisions of either bosonic or fermionic polar molecules are investigated. The Born-Oppenheimer adiabatic representation of the two-body dynamics provides both a qualitative classification scheme and a quantitative WKB quantization condition that predicts several sequences of resonant states. It is found that the near-threshold energy dependence of ultracold collision cross sections varies significantly with the particle exchange symmetry, with bosonic systems showing much smoother energy variations than their fermionic counterparts. Resonant variations of the angular distributions in ultracold collisions are also described. [Preview Abstract] |
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T1.00122: Dipole-dipole scattering in momentum space Vladimir Roudnev, Michael Cavagnero We consider a regularization procedure for dipole-dipole potential in momentum space. The kernel of the corresponding Lippmann-Schwinger equation can be represented in energy-independent form which reveals some universal properties both for low- and high-energy dipole-dipole scattering. [Preview Abstract] |
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T1.00123: A possible Efimov trimer in 3-component lithium 6 Pascal Naidon, Masahito Ueda We consider the Efimov trimer theory as a possible framework to explain recently observed losses by inelastic three-body collisions in a three-hyperfine-component ultracold mixture of lithium 6. Our results show that such a trimer state is indeed possible given the two-body scattering lengths in the three-component lithium mixture, and gives rise to two zero-energy resonances. The locations of these resonances appear to be consistent with observed losses. This would be the first observation of an Efimov trimer of distinguishable fermions. [Preview Abstract] |
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T1.00124: Many-Body Entangled Quantum Dynamics of Ultracold Molecules in Optical Lattices Michael Wall, Lincoln Carr Dynamical aspects of quantum phase transitions have long been restricted to mean field considerations due to lack of numerical tools. With the recent advent of Time-Evolving Block Decimation (TEBD), an entangled quantum dynamics algorithm, fully quantum studies of the dynamical aspects of many-body systems are now amenable to study. We present entangled quantum dynamics studies of the \emph{Molecular Hubbard Hamiltonian}, a novel lattice Hamiltonian which describes the essential many-body physics of closed-shell ultracold heteronuclear molecules in their absolute ground state in a quasi-one-dimensional optical lattice. This Hamiltonian is explicitly time-dependent, making a dynamic generalization of the concept of quantum phase transitions necessary. We demonstrate the presence of emergent time scales over which spatial entanglement grows, crystalline order appears, and oscillations between rotational states self-damp into an asymptotic superposition. We also demonstrate that these time scales are not, in general, monotonic functions of the parameters of the lattice. [Preview Abstract] |
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T1.00125: Spatially resolved imaging of the dipole-dipole energy exchange among ultracold Rydberg atoms Laura C. Popa, Michael W. Noel The dipole-dipole interaction allows ultracold highly-excited atoms to exchange energy over long distances. By exciting Rydberg atoms to two different states using a pair of crossed laser beams we localize the initial interaction to the region of intersection. Using a spatially sensitive ion detector, we then observe how this energy exchange evolves in time throughout the sample. [Preview Abstract] |
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