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 Q1: Ultracold Molecules I |
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Chair: Nick Bigelow, University of Rochester Room: Chemistry Building 402 |
Friday, May 22, 2009 8:00AM - 8:30AM |
Q1.00001: Ultracold Polar Molecules Invited Speaker: Ultracold polar molecules are new model quantum systems that promise study of quantum phase transitions, quantum simulations of condensed matter spin systems, and new schemes for quantum information. These proposals require a high phase-space-density gas of polar molecules where the electric dipole-dipole interaction is significant. We have recently created a gas of absolute ground-state polar molecules from a near quantum~degenerate gas of KRb Feshbach molecules using a single step of STImulated Raman Adiabatic Passage (STIRAP) state transfer. With no measurable heating in the transfer process, we created 4x10$^4$ ultracold polar molecules trapped in an optical dipole trap. The polar molecular gas has a peak density of 10$^{12}$ per cubic~centimeter~at a temperature of 350 nanoKelvin. The KRb molecules in the absolute ground state possess a permanent electric dipole~moment~that we measure to be 0.566(17) Debye. Currently, we are investigating the collisional stability of these molecules and seeing evidence for ultracold chemical reactions. This ability to create a quantum gas of ground-state molecules paves the way for future studies of dipolar Fermi gases and dipolar Bose-Einstein condensates. [Preview Abstract] |
Friday, May 22, 2009 8:30AM - 9:00AM |
Q1.00002: Ultracold triplet Rb$_{2}$ molecules in the rovibrational ground state Invited Speaker: The field of ultracold atoms has led to many interesting and fascinating developments in recent years. This success has also generated a quest for ultracold quantum degenerate ensembles of molecules. However, molecules have a complex inner structure and cannot be laser cooled. One pathway to cold molecules is to start with ultracold atoms and associate them via controlled collisions in molecular bonds. These molecules are typically weakly bound and quite fragile. We have developed a method to coherently change the molecular bond strength by efficiently transferring weakly bound Rb$_{2}$ molecules to their rovibrational ground state via a stimulated Raman transition. As a consequence, a nearly quantum degenerate gas of tightly bound Rb molecules is generated with new exciting perspectives for future experiments. [Preview Abstract] |
Friday, May 22, 2009 9:00AM - 9:30AM |
Q1.00003: Photoassociation of ultracold polar molecules in the rovibrational ground state Invited Speaker: Ultracold LiCs molecules in the absolute ground state X$^{1}\Sigma ^{+}$, v$\prime \prime $=0, J$\prime \prime $=0 are formed via a single photo-association step starting from laser-cooled atoms. The selective production of v$\prime \prime $=0, J$\prime \prime $=2 molecules with a 50-fold higher rate is also demonstrated. The rotational and vibrational state of the ground state molecules is determined in a setup combining depletion spectroscopy with resonant- enhanced multi-photon ionization time-of-flight spectroscopy. Using the determined production rate of up to 5 $\times $ 10$^{3}$ molecules/s, we describe a simple scheme which can provide large samples of externally and internally cold dipolar molecules. We analyze the formation of ultracold LiCs molecules in the rovibrational ground state through photoassociation into the B$^{1} \quad \Pi $ state. Absolute rate constants for photoassociation at large detunings from the atomic asymptote are determined and are found to be surprisingly large. The photoassociation process is modeled using a full coupled-channel calculation for the continuum state, taking all relevant hyperfine states into account. The enhancement of the photoassociation rate is found to be caused by an increased amplitude of the singlet scattering wave function at the inner turning point of the lowest triplet state a$^{3}\Sigma ^{+}$. This perturbation can be ascribed to the existence of a broad Feshbach resonance at low scattering energies. Our results elucidate the important role of couplings in the scattering wavefunction for the formation of deeply bound ground state molecules via photoassociation. [Preview Abstract] |
Friday, May 22, 2009 9:30AM - 10:00AM |
Q1.00004: Ultracold Heteronuclear Fermi-Fermi Molecules Invited Speaker: Spin mixtures of quantum-degenerate fermionic gases exhibit long lifetimes in the strongly-interacting regime near a Feshbach resonance. This has opened the door for numerous key experiments like the creation of Fermi-Fermi molecules, the realization of molecular BEC, the observation of a pairing gap and of superfluidity in a fermionic gas in the BEC-BCS cross-over region near a Feshbach resonance. We present the production of ${}^{6}\textrm{Li}$-${}^{40}\textrm{K}$ heteronuclear molecules based on our experimental platform for the production of a two-species mixture of quantum-degenerate Fermi gases [1]. We studied two s-wave Feshbach resonances between lithium and potassium at $155\,\mathrm{G}$ and $168\,\mathrm{G}$. By magnetic field sweeps we created about $4\times 10^{4}$ ${}^{6}\textrm{Li}$-${}^{40}\textrm{K}$ molecules at conversion efficiencies of up to $50\,\%$ [2]. With a Stern-Gerlach purification technique we are able to image molecules and atoms spatially separated from each other. We show an increased molecule lifetime close to resonance of more than 100 ms in the molecule-atom mixture.\newline [1] {M.~Taglieber \emph{et al.}, Phys. Rev. Lett. {\bf 100}, 010401 (2008).}\newline [2] {A.-C.~Voigt \emph{et al.}, Phys. Rev. Lett. {\bf 102}, 020405 (2009).} [Preview Abstract] |
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