Bulletin of the American Physical Society
38th Annual Meeting of the Division of Atomic, Molecular, and Optical Physics
Volume 52, Number 7
Tuesday–Saturday, June 5–9, 2007; Calgary, Alberta, Canada
Session C1: Cold Molecules |
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Sponsoring Units: DAMOP TGPMFC Chair: T. Bergeman, SUNY-Stony Brook Room: TELUS Convention Centre Macleod BC |
Wednesday, June 6, 2007 1:30PM - 2:06PM |
C1.00001: Molecular collision studies with Stark-decelerated beams Invited Speaker: Molecular scattering behavior has generally proven difficult to study at low collision energies. We formed a molecular beam of OH radicals with a narrow velocity distribution and a tunable absolute velocity by passing the beam through a Stark decelerator. The transition probabilities for inelastic scattering of the OH radiacls with Xe atoms were measured as a function of the collision energy in the range of 50 to 400 wavenumbers, with a high intrinsic energy resolution. The behavior of the cross-sections for inelastic scattering near the energetic thresholds was accurately measured, and excellent agreement was obtained with cross-sections derived from coupled- channels calculations on ab initio computed potential energy surfaces [Science 313 (2006) 1617-1620]. The possibilities to perform collision studies using either two Stark-decelerated beams in a crossed beam configuration or counter-propagating packets of molecules in a molecular synchrotron [Nature Physics, published online January 21, 2007; doi:10.1038/nphys513] will be discussed. Our experimental approach to the sympathetic cooling of polar molecules with ultra-cold Rb atoms will be presented as well. Time-permitting, measurements on the optical pumping of trapped polar molecules by black-body radiation [arXiv:physics/061221v] as well as our latest results on the electrodynamic (AC) trapping of, both, ground-state atoms and molecules [PRA 74 (2006) 063403] will be shown. [Preview Abstract] |
Wednesday, June 6, 2007 2:06PM - 2:42PM |
C1.00002: Experiments with Ultracold KRb and Rb$_{2}$ Molecules Invited Speaker: Ultracold molecules are of interest for a number of applications including ultracold chemistry, novel quantum degenerate systems, precision spectroscopy, and quantum computation. Photoassociation (PA) of ultracold atoms is a useful means of producing various diatomic molecular species at sub-mK temperatures. Heteronuclear systems have garnered particular attention because of their permanent electric dipole moments. We use PA to form both KRb and Rb$_{2}$, typically in high vibrational levels of either the singlet ground state ($X \quad ^{1}\Sigma ^{+})$ or lowest-lying triplet state ($a \quad ^{3}\Sigma ^{+})$. In KRb, a novel depletion spectroscopy is used to detect the molecules with both vibrational ($v)$ and rotational ($J)$ resolution. Monitoring the population of a specific $X$-state vibrational level $v''$ with pulsed two-photon ionization, we observe depletion when a cw laser drives a bound-bound transition from ($v''$, $J'')$ to an excited rovibrational level. This high-resolution spectroscopy is helping to guide Raman schemes to transfer ultracold molecules from high-$v''$ levels, produced by PA, to the absolute ground state, which is stable against inelastic collisions. We also use this depletion spectroscopy to precisely measure the ground-state dissociation energy of KRb. In Rb$_{2}$, we observe the effects of resonant coupling between excited 0$_{u}^{+}$ states on ground-state molecule formation. We photoassociate to 0$_{u}^{+}$ levels below the 5$S$ + 5$P_{1/2}$ limit and state-selectively detect the resulting ground-state molecules by two-photon ionization. In the absence of resonant coupling between the two 0$_{u}^{+}$ potentials (converging to the 5$S$ + 5$P_{1/2}$ and 5$S$ + 5$P_{3/2}$ limits), the excited molecules would spontaneously decay overwhelmingly to the highest $v''$ levels, bound by $<$ 1 cm$^{-1}$. The effect of resonant coupling is to provide selected 0$_{u}^{+}$ wavefunctions with increased short-range amplitude, which enhances their decay to more deeply bound levels. Progress towards optical trapping and collisional studies of Rb$_{2}$ will also be reported. [Preview Abstract] |
Wednesday, June 6, 2007 2:42PM - 3:18PM |
C1.00003: New theoretical findings on cold molecules in optical lattices Invited Speaker: There are great expectations for the application of ultra-cold molecules in simulating many-body states and performing high-precision measurements. All these applications are based on optical lattices to hold molecules in fixed spatial locations. Optical lattices are constructed from the interference patterns of counter-propagating laser beams. They provide a periodic potential for ultracold particles. The parameters of the lattice can be externally controlled by tuning the frequency and intensity of the lasers. In addition, the interaction strength between polar molecules can be tuned by external DC electric or magnetic fields. There are many things that have to be found about polar molecules in optical lattices before these goals are reached. In particular, I have focused on determining the most efficient ways to produce molecules from ultra-cold atoms in optical lattices. I will discuss conditions for strong confinement of molecules in a lattice, suppression of undesired perturbations that cause loss of atoms and molecules from the lattice, and control interactions between neighboring molecules. In addition, I will show our results on the differential AC Stark shift of various ro-vibrational levels of the ground-state molecules caused by the optical lattice. The analysis of Stark shifts are essential for selection of vibrational levels with matched polarizabilities as necessary for high-precision frequency measurements. I acknowledge support of this work from a grant of the Army Research Office. [Preview Abstract] |
Wednesday, June 6, 2007 3:18PM - 3:54PM |
C1.00004: Creating and confining ultracold polar molecules Invited Speaker: We describe our work on the creation of ultracold (T$\sim $ 200 $\mu $K) NaCs molecules. Our experiments start with electronic ground-state NaCs molecules created by photoassociation of laser cooled and trapped Na and Cs atomic vapors held in a two-species magneto-optical trap. Using state-resolved photoassociation followed by resonantly enhanced multi-photon ionization we have carried out a detailed spectroscopic study of this system and show that a significant number of deeply bound singlet-state molecules can be created. We then describe our recent success in trapping the singlet molecules. Finally, we discuss approaches to manipulate the state of these molecules using a laser-controlled state transfer scheme. [Preview Abstract] |
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