Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session M1: Cold Chemistry |
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Chair: Kaden Hazzard, JILA Room: Grand Ballroom BCD |
Thursday, June 7, 2012 8:00AM - 8:12AM |
M1.00001: Systematic analysis of long-range interactions between vibrating polar bialkali molecules Olivier Dulieu, Romain Vexiau, Maxence Lepers, Mireille Aymar, Nadia Bouloufa The determination of the long-range anisotropic interactions between polar bialkali molecules is of crucial importance for the achievement of a quantum gas of ultracold polar molecules. In particular, the dispersion coefficient C$_6$ of the van der Waals interaction depends on the dynamic polarizability of the molecule evaluated at imaginary frequencies, expressed as a sum over all possible radiative transitions of electronic dipole moments. Using a mixture of up-to-date spectroscopic data and accurate ab initio data for potential energy curves, and permanent and transition dipole moments, we have obtained the values of the dispersion coefficients between identical polar molecules (LiNa, LiK, LiRb, LiCs, NaK, NaRb, NaCs, KRb, KCs, RbCs) in an arbitrary vibrational level of their electronic ground state. A careful analysis of the importance of the various kinds of transitions contributing to the sum has been performed. The C$_6$ values significantly decrease with increasing vibrational levels towards the sum of the C$_6$ coefficients between the four involved atomic pairs. For the lowest vibrational levels the C$_6$ parameter varies from about 10$^4$ atomic units for KRb up to 10$^7$ atomic units for NaCs, which will lead to different collisional regimes at ultracold temperature. [Preview Abstract] |
Thursday, June 7, 2012 8:12AM - 8:24AM |
M1.00002: \"Uber-Resonant Scattering of Ultracold Molecules Michael Mayle, Brandon P. Ruzic, John L. Bohn Compared to purely atomic collisions, ultracold collisions involving molecules have the potential to support a much larger number of Fano-Feshbach resonances due to the huge amount of ro-vibrational states available. For example, for Rb+KRb collisions we expect tens to hundreds resonances within one Gauss of magnetic field, depending on the partial wave of the collision. In order to handle such ultracold atom-molecule collisions, we formulate a theory that incorporates the ro-vibrational Fano-Feshbach resonances in a statistical manner while treating the physics of the long-range scattering, which is sensitive to such things as hyperfine states, collision energy and any applied electromagnetic fields, exactly within multichannel quantum defect theory. Uniting these two techniques, we can assess the influence of ``\"uber-resonant'' scattering in the threshold regime, and in particular its dependence on the hyperfine state selected for the collision. This allows us to explore effects such as the onset of so-called Ericson fluctuations, which are well-known in nuclear physics but completely new in the ultracold domain. [Preview Abstract] |
Thursday, June 7, 2012 8:24AM - 8:36AM |
M1.00003: Dynamics of strongly reactive molecules Michael Foss-Feig, Ana Maria Rey As degenerate gases of ground-state polar molecules approach realization [1], it is increasingly important to understand the effects of lossy interactions on quantum simulations. We explore the dynamics of strongly reactive molecules in a variety of lattice geometries, and point out ways in which losses can be used as ideal probes of these systems. We further explore the use of losses as projective measurements onto entangled subspaces [2], and discuss realistic implementations of these ideas with ground-state molecules. \\[4pt] [1] A. Chotia et al., arXiv:1110.4420[physics.atom-ph] (2011)\\[0pt] [2] B. Kraus et al., Phys. Rev. A 78, 042307 (2008) [Preview Abstract] |
Thursday, June 7, 2012 8:36AM - 8:48AM |
M1.00004: Frenkel biexcitons in optical lattices with polar molecules Marina Litinskaya, Ping Xiang, Roman Krems Rotational excitation of ultracold polar molecules trapped on an optical lattice produces rotational Frenkel excitons (collective rotational excitations) [1]. We show that non-linear interactions between these excitons can be tuned by applying a dc electric field. We show that, at electric fields greater than a critical value, rotational Frenkel excitons form bound pairs -- biexcitons [2]. Frenkel biexcitons are strongly correlated states of two collective excitations in a molecular crystal, which are exceedingly hard to create and observe in solid-state crystals. We demonstrate that the binding energy of the rotational biexcitons can be controlled by tuning the angle between the applied field and the molecular array. Frenkel biexcitons can be used for many applications ranging from the controlled preparation of entanglement between quasi-particles to the study of bipolarons. \\[4pt] [1] ``Frenkel biexcitons in optical lattices with polar molecules,'' Ping Xiang, M. Litinskaya, R. V. Krems; cond-mat/1112.3942. \\[0pt] [2] ``Tunable disorder in a crystal of cold polar molecules,'' F. Herrera, M. Litinskaya, R. V. Krems, Phys. Rev. A 82, 033428 (2010). [Preview Abstract] |
Thursday, June 7, 2012 8:48AM - 9:00AM |
M1.00005: Spectroscopy of $^{39}$K$^{85}$Rb electronic states in the predicted region of resonantly coupled excited states for the direct formation of the $X$(0,0) state Jayita Banerjee, David Rahmlow, Ryan Carollo, Michael Bellos, Matthew Bermudez, Edward Eyler, Philip Gould, William Stwalley The 2$^{1}\Pi $(v$\prime $=17) and 1$^{1}\Pi $(v$\prime $=60) vibrational levels of KRb are predicted to be resonantly coupled, based on extrapolation from high rotational levels reported in [1] to \textit{J$\prime $ }=1 [2], and on tentative assignments of photoassociation spectra in the region near 12535cm$^{-1}$ [3]. Access to the 2$^{1}\Pi $ levels is desirable for formation of ultracold KRb molecules in their ground $X^{1}\Sigma ^{+}$, v=0, J=0 level because of strong Franck-Condon overlap [3]. The 1$^{1}\Pi $ component of these two mixed states provides PA access to short range region where 2$^{1}\Pi $ emission to the $X$(0,0) level can occur. Experiments are being carried out to better understand the spectra and perturbations in the region near 12535cm$^{-1}$, which should include 3(0$^{+})$, 2(1), 4(1), 5(1) and possibly other states. The 4(1) and 5(1) long-range states correlate with 1$^{1}\Pi $ and 2$^{1}\Pi $ short-range states. These studies have also produced new information on efficient formation of specific vibrational levels in a$^{3}\Sigma ^{+}$ state and new data on 3$^{3}\Sigma ^{+ }$and 3$^{3}\Pi $ states. \\[4pt] [1] Kasahara et al., JCP 111, 19 (1999)\\[0pt] [2] Wang et al, EPJD 31, 165 (2004)\\[0pt] [3] Stwalley et al., JPCA 114, 81 (2010) [Preview Abstract] |
Thursday, June 7, 2012 9:00AM - 9:12AM |
M1.00006: Rovibrational Optical Pumping of NaCs Marek Haruza, Patrick Zabawa, Amy Wakim, Nicholas Bigelow We demonstrate efficient cooling of the rotational degree of freedom of ultracold NaCs molecules through narrow line optical pumping. Molecules in v''=0, N''=2 and 4 are excited to the lowest vibrational level of the $A^1\Sigma^+-b^3\Pi$ complex from which they decay to v''=0, N''=0. We achieve cooling of both rotational and vibrational degrees of freedom by applying this technique in conjunction with broadband optical pumping [1]. This technique also allows transfer of population between any of the lowest vibrational states (v''=0-2) at kHz rates.\\[4pt] [1] D. Sofikitis, R. Horchani, X. Li, M. Pichler, M. Allegrini, A. Fioretti, D. Comparat, and P. Pillet, Phys. Rev. A 80, 051401(R) (2009) [Preview Abstract] |
Thursday, June 7, 2012 9:12AM - 9:24AM |
M1.00007: Threshold resonances in ultracold chemical reactions Robin C\^ot\'e, Ionel Simbotin, Subhas Ghosal We analyze the effects of near threshold resonances on the low energy behavior of cross sections for reactive scattering systems with reaction a barrier ({\em e.g.} Cl + H$_2$, D + H$_2$). We find an anomalous behavior when a resonance pole is very close to the threshold of the entrance channel. For inelastic processes, including reactive ones, the anomalous energy dependence of the cross sections is given by $\sigma\sim E^{-3/2}$. However, at vanishingly low energies, the standard Wigner's threshold behavior ($\sigma\sim E^{-1/2}$) is eventually recovered, but limiting to much narrower range of energies. When the cross sections are averaged to obtain rate coefficients, the anomalous behavior persists; indeed, we find an intermediate regime of ultralow temperatures, where the inelastic rate coefficients behave as $K\sim 1/T$. [Preview Abstract] |
Thursday, June 7, 2012 9:24AM - 9:36AM |
M1.00008: Photoassociation of alkali tetramers into high vibrational states Jason Byrd, Subhas Ghosal, John Montgomery, Jr, Robin C\^ot\'e he formation of alkali tetramers in high vibrational states from two polar molecules, XY$+$XY$\rightarrow$X${}_2$Y${}_2$, using photoassociation has been investigated for various species. Diatom-diatom interaction surfaces have been calculated using {\it ab initio} equation of motion coupled cluster and time dependent density functional van der Waals methods. Using an external electric field to improve the associated Franck Condon factors, we propose a two color time dependent wavepacket scheme to probe the high vibrational level states of various alkali tetramers. [Preview Abstract] |
Thursday, June 7, 2012 9:36AM - 9:48AM |
M1.00009: Molecule-molecule hyperfine Feshbach resonances Alisdair Wallis, Roman Krems Magnetic Feshbach scattering resonances play a central role in experimental research of atomic gases at ultracold temperatures. A major thrust of current research is to create an ultracold gas of diatomic alkali-metal molecules in the ground rovibrational state of the ground electronic $^1\Sigma$ state. Can ultracold $^1\Sigma$ molecules be controlled by means of magnetic Feshbach resonances? Unlike alkali metal atoms, $^1\Sigma$ diatomic molecules have no unpaired electrons. The response of $^1\Sigma$ molecules to an external magnetic field is determined entirely by the spin structure of the atomic nuclei. We present the first calculations of molecule-molecule collisions for $^1\Sigma$ molecules in a magnetic field. In particular, we calculate the rates of hyperfine relaxation in molecule - molecule collisions and explore the possibility of tuning magnetic Feshbach resonances in an ultracold gas of $^{87}$Rb$^{133}$Cs(X$^1\Sigma^+$) molecules. [Preview Abstract] |
Thursday, June 7, 2012 9:48AM - 10:00AM |
M1.00010: Cold dipolar collisions in magnetically trapped OH Benjamin Stuhl, Mark Yeo, Matt Hummon, Jun Ye A major open question in cold molecular physics is the universality of dipole-dipole scattering in real molecules. So far, the relationship between dipole strength and scattering cross-section has been investigated in only one system, ultracold KRb in its absolute ground state. We now report evidence for inelastic dipole-dipole scattering in magnetically trapped metastable OH molecules under a polarizing electric field, with an apparent $d^2$ dependence rather than the $d^6$ law observed in optically trapped KRb. [Preview Abstract] |
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