Bulletin of the American Physical Society
39th Annual Meeting of the APS Division of Atomic, Molecular, and Optical Physics
Volume 53, Number 7
Tuesday–Saturday, May 27–31, 2008; State College, Pennsylvania
Session U1: Creating and Manipulating Ultracold Heteronuclear Molecules |
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Chair: Laurence Pruvost, Lab Aime Cotton Room: Nittany Lion Inn Ballroom CDE |
Saturday, May 31, 2008 8:00AM - 8:36AM |
U1.00001: Rovibrational Dynamics and Photoassociation of Cold Heteronuclear Dimers in Electric Fields Invited Speaker: We investigate the effects of a strong static electric field on the rovibrational spectra of diatomic heteronuclear molecules in their electronic ground state. A full rovibrational approach is developed and applied including the coupling of the vibrational and rotational motions and taking into account the dependence of the electric dipole moment on the internuclear distance. For several alkali dimers, LiCs, LiRb, NaCs, KRb and RbCs [1,2], a detailed analysis of the impact of the electric field is performed: the orientation, the hybridization of the angular momenta and the squeezing of the vibrational motion of the highly excited levels close to the dissociation threshold are anaylzed. In addition, we discuss the formation of ultracold molecules via stimulated emission followed by a radiative deexcitation cascade in the presence of a static electric field [3,4]. By analyzing the corresponding cross sections for the LiCs molecule, we show the possibility to populate the lowest rotational excitations via photoassociation. The modification of the radiative cascade due to the electric field leads to narrow rotational state distributions in the vibrational ground state. External fields might therefore represent an additional valuable tool towards the ultimate goal of quantum state preparation of molecules. \newline \newline [1] R. Gonzalez-Ferez, M. Mayle, \& P. Schmelcher, Chem. Phys. {\bf 329} 203 (2006) \newline [2] R. Gonzalez-Ferez et al, preprint (2008) \newline [3] R. Gonzalez-Ferez, M. Mayle, \& P. Schmelcher, Europhys. Lett. {\bf 78}, 53001 (2007) \newline [4] R. Gonzalez-Ferez, M. Weidem\"uller, \& P Schmelcher, Phys. Rev. A {\bf 76}, 023402 (2007) [Preview Abstract] |
Saturday, May 31, 2008 8:36AM - 9:12AM |
U1.00002: Heteronuclear K-Rb mixtures with tunable interactions Invited Speaker: Quantum degenerate atomic mixtures with tunable interactions are promising for the production of quantum gases of polar molecules. These compound particles would enrich the physics of ultracold systems, since they have many more degrees of freedom than atoms and a controllable anisotropic, long range interaction. In this context, K-Rb mixtures are appealing, since both fermion-boson and boson-boson pairs are available, the main isotopic combinations present several Feshbach resonances, and the ground state dimer has a relatively large electric dipole moment. We have exhaustively characterized the scattering properties of different K-Rb systems by means of Feshbach spectroscopy. This has allowed us to construct an accurate near-threshold model for scattering and bound-state calculations able to determine precisely near threshold parameters for all K-Rb pairs. The model can be used to predict with high precision the behavior of still unexplored mixtures and, combining it with information about the short range part of the interaction potential, to develop schemes for efficient transfer of Feshbach molecules to their ground state. This work was carried out in collaboration with G. Modugno, C. D'Errico, M. Fattori, G. Roati, A. Simoni and M. Inguscio. [Preview Abstract] |
Saturday, May 31, 2008 9:12AM - 9:48AM |
U1.00003: Creation of heteronuclear Feshbach molecules with $^{85}$Rb and $^{87}$Rb Invited Speaker: We will report on the creation of ultracold heteronuclear Feshbach molecules. Heteronuclear molecules in low-lying vibrational states are particularly interesting since they are predicted to exhibit a permanent dipole moment due to the unequal distribution of electrons. Although no significant permanent dipole moment is expected to exist in a $^{85}$Rb -- $^{87}$Rb molecule, our work demonstrates a first step toward the efficient production of ground-state ultracold heteronuclear molecules. Starting with a $^{87}$Rb BEC and a cold thermal gas of $^{85}$Rb, we utilize previously unobserved interspecies Feshbach resonances to create up to 25,000 molecules. The presence of two species with different quantum degeneracy provides a rich system for testing our understanding of the conversion efficiency from atoms to molecules. We can also create a simultaneously Bose-condensed sample of $^{85}$Rb and $^{87}$Rb. The effects of immiscibility in this two-component quantum fluid on the creation of heteronuclear molecules will be discussed. [Preview Abstract] |
Saturday, May 31, 2008 9:48AM - 10:24AM |
U1.00004: Cold Controlled Chemistry Invited Speaker: The development of experimental techniques for controlling chemical reactions externally has long been a major research goal in chemical physics. Many ground-breaking experiments demonstrated the possibility of controlling uni-molecular reactions by laser fields. External field control of bi-molecular chemical reactions, however, remains a significant challenge. External control of bi-molecular reactions is complicated by thermal motion of molecules that randomizes molecular encounters and diminishes the effects of external fields on molecular collisions. The effects of the thermal motion can be reduced by cooling molecular gases to low temperatures. Electromagnetic fields may influence molecular collisions significantly only when the translational energy of the molecules is smaller than the perturbations due to interactions with external fields. Static magnetic and electric fields as well as off-resonant laser fields readily available in the laboratory shift molecular energy levels by up to a few Kelvin so external field control of gas-phase molecular dynamics can be most easily achieved at temperatures near or less than one Kelvin. The purpose of this talk is to demonstrate that molecular collisions at low temperatures can be effectively controlled with static and laser electromagnetic fields and discuss possible applications of external field control of molecular collisions in cold gases. I will discuss molecular collisions at both cold ($\sim 1$ Kelvin) and ultracold ($< 1$ milliKelvin) temperatures. I will demonstrate that static electric fields can be used to tune scattering resonances in ultracold gases and modify chemical reactions of cold and ultracold molecules. I will show that superimposed electric and magnetic fields may dramatically alter collision dynamics of cold molecules in a magnetic trap and describe interactions of molecules in a microwave laser cavity. Finally, I will argue that confining the motion of ultracold molecules by laser fields to two dimensions may suppress inelastic collisions and chemical reactions at ultracold temperatures and present results indicating that inelastic collisions of confined atoms or molecules in weak electromagnetic fields may be controlled by varying the orientation of the external field axis with respect to the plane of confinement. [Preview Abstract] |
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