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 W2: Ultracold Collisions, Photoassociation, and Spectroscopy |
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Chair: Michael Lim, Rowan University Room: Gilmer Hall 130 |
Saturday, May 23, 2009 8:00AM - 8:12AM |
W2.00001: Collision and evaporation dynamics of different isotopes of Sr Y. Natali Martinez de Escobar, Pascal Mickelson, Mi Yan, Thomas Killian We study the collision and evaporation dynamics of both bosonic and fermionic isotopes of strontium (Sr) in a 1064 nm optical dipole trap. Because of the small $s$-wave scattering length for the bosonic $^{88}$Sr isotope, the elastic-scattering cross section depends strongly on collisional energies. Extending this model to other abundant isotopes and isotope mixtures allows us to determine effective collisional behavior and guides our progress toward quantum degeneracy in Sr. [Preview Abstract] |
Saturday, May 23, 2009 8:12AM - 8:24AM |
W2.00002: Collisions and atom loss in ultracold, strongly interacting Na-Li mixtures Jae H. Choi, Caleb A. Christensen, Gyu-Boong Jo, Ye-ryoung Lee, Tout Wang, Tony H. Kim, David E. Pritchard, Wolfgang Ketterle We report on our progress in the production of ultracold heteronuclear molecules and in the studies of strongly interacting Bose-Fermi mixtures. Ultracold gases of $^{6}$Li and $^{23}$Na in their lowest hyperfine states are prepared in an optical dipole trap near the heteronuclear Feshbach resonance at 796~G, where interesting phenomena such as heteronuclear molecule formation and phase separation could be explored. We present results on $^{6}$Li-$^{23}$Na collisions and atom losses in the system. [Preview Abstract] |
Saturday, May 23, 2009 8:24AM - 8:36AM |
W2.00003: The Effect of Sinusoidal Spectral Phase on Photoassociation followed by Excitation Hyounguk Jang, Marc L. Trachy, Giorgi Veshapidze, Charles W. Fehrenbach, Brett D. DePaola In recent years, the development of ultrafast lasers and quantum control techniques has enhanced the ability to control the interaction between light and matter. In this work we explore the effects of a sinusoidally varying spectral phase on photoassociation followed by excitation (PAE). The measurement consists of using a narrow bandwidth laser to excite the molecular states formed through PAE to autoionizing states, which are then measured with time-of-flight spectroscopy. We observe that the PAE process is an extremely strong function of the sinusoidal spectral phase, showing a contrast ratio in excess of 100. [Preview Abstract] |
Saturday, May 23, 2009 8:36AM - 8:48AM |
W2.00004: Theoretical studies of reaction rates for the Rb-NH system Daniel Haxton, Steven Wrathmall, Heather Lewandowski, Chris Greene We present the results of ab initio calculations on the Rb-NH system. We are interested both in ultracold collisions of Rb and NH and in higher-energy collisions more typical of chemical reactive scattering. We have constructed a set of sixteen unique two-dimensional potential energy surfaces, including the spin-orbit interaction, using the COLUMBUS quantum chemistry package. For the moment we fix the NH bond distance. The sixteen surfaces include the charge-transfer state Rb$^+$ + NH$^-$, which becomes the ground state at small Rb-NH separations, and also the channel Rb ($^2S$) + NH ($^1\Delta$), which enjoys a near degeneracy with the spin-orbit split components of Rb ($^2P$) + NH (X $^3\Sigma^-$). A property-based diabatization is employed, after which we perform reactive scattering calculations using the R-matrix propagator method. Our results indicate that transitions between the nearly degenerate channels are indeed highly favored. [Preview Abstract] |
Saturday, May 23, 2009 8:48AM - 9:00AM |
W2.00005: Technique for Rapid Raman Spectrography of Cold Alkali Vapors. Fredrik Fatemi, Matthew Terraciano, Zachary Dutton, Mark Bashkansky We demonstrate a simple technique for single-shot imaging of magnetic sublevel distributions in cold atoms. The technique relies on velocity-selective stimulated Raman transitions in a magnetic field. The Raman transitions couple sublevels between the two hyperfine manifolds so that each possible transition pathway is resonant only for a specific velocity. Cold atoms expanding from a magneto-optical trap are exposed to a brief ($\sim $1ms) counterpropagating pulse in a lin-perp-lin configuration. Ballistic expansion of the atom sample separates the atoms according to their velocities, so that the each sublevel's population is easily observed using fluorescence imaging from cycling transition light. We demonstrate this technique for a variety of optical pumping configurations in both Rb85 and Rb87. [Preview Abstract] |
Saturday, May 23, 2009 9:00AM - 9:12AM |
W2.00006: Precise multiwavelength differential light shift measurements in lattice-trapped $^{87}$Rb Nathan Lundblad, Radu Chicireanu, Karl Nelson, Malte Schlosser, William Phillips, Trey Porto There has been considerable recent interest in finding a ``magic wavelength" for hyperfine (microwave) transitions for atoms confined in optical lattices. Magic wavelength predictions exist for Al and Ga, but predictions for the alkalis (Rb and Cs) have met with some controversy, and it is likely that they do not exist in traditional optical lattices. In the interest of elucidating some of the issues, we present preliminary results of a precision multi-wavelength study of light shifts in lattice-trapped Rb, focusing particularly on the differential light shift between the ground-state hyperfine levels $F=1,2$. [Preview Abstract] |
Saturday, May 23, 2009 9:12AM - 9:24AM |
W2.00007: Mapping the composite character of magnetically trapped Rydberg atoms Peter Schmelcher, Michael Mayle, Igor Lesanovsky By investigating the quantum properties of magnetically trapped $nS_{1/2}$ Rydberg atoms, it is demonstrated that the composite nature of Rydberg atoms significantly alters their trapping properties opposed to point-like particles with identical magnetic moment. Employing an off-resonant two photon coupling scheme, a setup is proposed which allows to observe the signatures of the rydberg trapping potential using a gas of ground state atoms. In addition, such a scheme provides new possibilities for designing trapping potentials for ground state atoms. Simulated time-of-flight pictures mirroring the experimental situation are provided. [Preview Abstract] |
Saturday, May 23, 2009 9:24AM - 9:36AM |
W2.00008: Two body and multibody interaction in a cold Rydberg gas Jianing Han, Tom Gallagher Cold Rydberg atoms trapped in a Magneto Optical Trap (MOT) are not isolated and they tend to bond through dipole-dipole and multiple-multiple interactions between Rydberg atoms. The dipole-dipole interaction and van der Waals interaction between two atoms have been intensively studied. However, the fact that the dipole-dipole interaction and van der Waals interaction show the same size of broadening, studied by Raithel's group, and there is transition between two molecular states, studied by Farooqi and Overstreet, can not be explained by the two atom picture. The purpose of this paper is to show the multibody nature of a dense cold Rydberg gas by studying the molecular state microwave spectrum. Specifically, single body, two body and three body interaction regions are separated. Moreover, the multibody energy levels for selected geometries are calculated. In addition, multibody blockade will be discussed. \\[3pt] [1] A. Reinhard, K. C. Younge, T. Cubel Liebisch, B. Knuffman, P. R. Berman, and G. Raithel, Phys. Rev. Lett. {\bf 100}, 233201 (2008).\\[0pt] [2] S.M. Farooqi, D. Tong, S. Krishnan, J. Stanojevic,Y.P. Zhang, J.R. Ensher, A.S. Estrin, C. Boisseau, R. Cote, E.E. Eyler, and P.L. Gould, Phys. Rev. Lett. {\bf 91}, 183002 (2003).\\[0pt] [3] K. Richard Overstreet, Arne Schwettmann, Jonathan Tallant, and James P. Shaffer, Phys. Rev. A {\bf 76}, 011403 (2007). [Preview Abstract] |
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