Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session M3: Focus: Cold and Ultracold MoleculesFocus
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Chair: Brian Odom, Northwestern University Room: Ballroom D |
Thursday, May 26, 2016 8:00AM - 8:30AM |
M3.00001: Cold molecules, collisions and reactions Invited Speaker: Johannes Hecker Denschlag I will report on recent experiments of my group where we have been studying the formation of ultracold diatomic molecules and their subsequent inelastic/ reactive collisions. For example, in one of these experiments we investigate collisions of triplet Rb$_2$ molecules in the rovibrational ground state. We observe fast molecular loss and compare the measured loss rates to predictions based on universality. In another set of experiments we investigate the formation of (BaRb)$^+$ molecules after three-body recombination of a single Ba$^+$ ion with two Rb atoms in an ultracold gas of Rb atoms \footnote{ Energy scaling of cold atom-atom-ion three-body recombination, A. Kr\"{u}kow, A. Mohammadi, A. H\"{a}rter, J. Hecker Denschlag, J. Perez-Rios, and C. H. Greene arXiv:1510.04938 (2015).}. Our investigations indicate that the formed (BaRb)$^+$ molecules are weakly bound and that several secondary processes take place ranging from photodissociation of the (BaRb)$^+$ molecule to reactive collisions with Rb atoms. I will explain how we can experimentally distinguish these processes and what the typical reaction rates are. [Preview Abstract] |
Thursday, May 26, 2016 8:30AM - 9:00AM |
M3.00002: Probabilistic rotational state preparation of a single molecular ion though consecutive partial projection measurements Invited Speaker: Michael Drewsen Fully quantum state prepared molecular ions are of interest for a wide range of research fields, including ultra-cold chemistry, ultra-high resolution spectroscopy for test of fundamental physics, and quantum information science. Cooling of the translational degrees of freedom of trapped molecular ions into the millikelvin range has become routine through Coulomb interactions with simultaneously trapped and Doppler laser-cooled atomic ions [1], and recently it has even become possible to prepare a single molecular ion in its absolute ground state with respect to its quantized motion in the external trapping potential [2-4]. With respect to the internal rovibrational degrees of freedom, significant progress towards single quantum state preparation has as well recently been realized by a series of complementary methods [5-10]. In the talk, a novel method for probabilistic rotational state preparation of polar molecular ions based on consecutive partial projection measurements will be discussed. Results of state preparation of vibrational cold single MgH$^{+}$ ions in the rotational ground or first excited state with maximum likelihood estimated populations of 0.98 and 0.95, respectively, will be presented. [1] M{\o}lhave, K. and Drewsen, M. Phys. Rev. \textbf{A 62}, 011401 (2000). [2] Poulsen G., PhD thesis: ``Sideband Cooling of Atomic and Molecular Ions", Department of Physics and Astronomy, Aarhus University, 2011. [3] Wan Y. \textit{et al}., Phys. Rev. A \textbf{91}, 043425 (2015). [4] Rugango R. \textit{et al}., New J. Phys. \textbf{17}, 03009 (2015). [5] Staanum, P. F. \textit{et al}., Nat. Phys. \textbf{6}, 271 (2010). [6] Schneider, T. \textit{et al}., Nat. Phys. \textbf{6}, 275 (2010). [7] Tong, X., Winney, A. H., and Willitsch, S., Phys. Rev. Lett. \textbf{105}, 143001 (2010). [8] Rellergert, W. G. \textit{et al}., Nature \textbf{495}, 490 (2013). [9] Hansen A. K. \textit{et al}., Nature \textbf{508}, 76 (2014). [10] Lien, C.-Y. \textit{et al}., Nat. Commun.\textbf{ 5}, 4783 (2014). [Preview Abstract] |
Thursday, May 26, 2016 9:00AM - 9:12AM |
M3.00003: Long Hyperfine Coherence Time of Ultracold Fermionic $^{23}$Na$^{40}$K Molecules Jee Woo Park, Zoe Yan, Huanqian Loh, Sebastian Will, Martin Zwierlein Ultracold molecules created and trapped at sub uK temperatures allow the full control of the molecule’s external and internal degrees of freedom down to a single hyperfine state. In particular, an ensemble of molecules all initialized in a single rotational and hyperfine state can be prepared and be coherently addressed using microwave fields. In this talk, we report on the observation of long coherence time between two hyperfine states of fermionic $^{23}$Na$^{40}$K molecules in the ro-vibronic ground state ($v{=}0$, $J{=}0$). A direct two-photon microwave transition via the $J{=}1$ state is used to prepare a superposition of two lowest hyperfine states of $J{=}0$, and we perform Ramsey spectroscopy as a direct probe of phase coherence between these states. The fermionic nature of the molecules and the lack of electronic angular momentum in the ro-vibronic ground state heavily suppress the decoherence from collisions and external fields, respectively, and we observe long coherence times upto 0.5 sec for this hyperfine superposition state. The observed long coherence time is a crucial step for applications of trapped dipolar molecules in quantum information processing schemes. [Preview Abstract] |
Thursday, May 26, 2016 9:12AM - 9:24AM |
M3.00004: Photodissociation of quantum state-selected diatomic molecules yields new insight into ultracold chemistry Mickey McDonald, Bart H. McGuyer, Chih-Hsi Lee, Florian Apfelbeck, Tanya Zelevinsky When a molecule is subjected to a sufficiently energetic photon it can break apart into fragments through a process called ``photodissociation’’. For over 70 years this simple chemical reaction has served as a vital experimental tool for acquiring information about molecular structure, since the character of the photodissociative transition can be inferred by measuring the 3D photofragment angular distribution (PAD). While theoretical understanding of this process has gradually evolved from classical considerations to a fully quantum approach, experiments to date have not yet revealed the full quantum nature of this process. In my talk I will describe recent experiments involving the photodissociation of ultracold, optical lattice-trapped, and fully quantum state-resolved $^{88}Sr_2$ molecules. Optical absorption images of the PADs produced in these experiments reveal features which are inherently quantum mechanical in nature, such as matter-wave interference between output channels, and are sensitive to the quantum statistics of the molecular wavefunctions. The results of these experiments cannot be predicted using quasiclassical methods. Instead, we describe our results with a fully quantum mechanical model yielding new intuition about ultracold chemistry. [Preview Abstract] |
Thursday, May 26, 2016 9:24AM - 9:36AM |
M3.00005: Laser cooling and slowing of CaF molecules Stefan Truppe, Hannah Williams, Moritz Hambach, Ben Sauer, Ed Hinds, Mike Tarbutt We have developed a cold and bright source for CaF molecules and use laser radiation pressure to slow the molecules to within the capture velocity of a magneto-optical trap (MOT). Using laser ablation of Ca into a continuous flow of cryogenic Helium buffer gas mixed with SF$_6$ we produce up to 10$^{11}$ molecules per steradian per pulse in a single rotational state. The molecules move with a mean forward velocity of 160m/s and have a velocity spread of 80m/s. We then apply laser radiation pressure to the molecular beam to slow and cool the molecules. We form a quasi-closed laser-cooling cycle by using a main cooling laser to drive the $B^2\Sigma^+(v'=0)$ - $X^2\Sigma^+(v''=0)$ transition and a single repump laser to address the $A^2\Pi_{1/2}(v'=0)$-$X^2\Sigma^+(v''=1)$ transition. Radio-frequency sidebands applied to both lasers address the hyperfine structure. By chirping the frequencies of both lasers to keep the decelerating molecules resonant with the light, we scatter more than 10000 photons and reduce the speed to below 50 m/s. We achieve a similar effect by broadening the linewidth of the laser to several hundred MHz. This "white-light'' slowing is compared to the chirped slowing technique. We also present progress towards a MOT of CaF molecules. [Preview Abstract] |
Thursday, May 26, 2016 9:36AM - 9:48AM |
M3.00006: Radiation Pressure Force from Optical Cycling on a Polyatomic Molecule SrOH Ivan Kozyryev, Louis Baum, Kyle Matsuda, Alex Sedlack, Boerge Hemmerling, John Doyle Polyatomic molecules hold promise for many applications in physics and chemistry due to their rotational and vibrational degrees of freedom. The starting point for our approach to the production of ultracold strontium monohydroxide (SrOH) is buffer-gas cooling [1] followed by laser manipulation. Linear geometry, diagonal Franck-Condon factors, short radiative lifetimes and unresolved hyperfine splittings make SrOH a particularly attractive candidate for direct laser cooling. We report deflection of the SrOH beam through radiative force from optical cycling on the $\tilde{X}^{2}\Sigma^{+}\leftrightarrow\tilde{A}^{2}\Pi_{1/2}$ transition. We observe $\times12$ fluorescence enhancement with closed spin-rotation splitting and demonstrate cycling between different vibrational levels with the ${\rm Sr}\leftrightarrow{\rm O}$ mode repumping laser. Observed deflection and detection signals correspond to the scattering of $\sim100$ photons. Additional repumping laser for the bending mode would lead to scattering of $\sim1,000$ photons allowing for transverse laser cooling of the SrOH beam. We will also describe our experimental efforts towards laser slowing and trapping of SrOH. [1] I. Kozyryev, L. Baum, K. Matsuda, P. Olson, B. Hemmerling and J. M. Doyle, New J. Phys. 17 (2015) 045003. [Preview Abstract] |
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