Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session K02: Cold and Ultracold MoleculesInvited Live
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Chair: Wes Campbell, UCLA |
Wednesday, June 2, 2021 10:30AM - 11:00AM Live |
K02.00001: Quantum effects in cold collisions Invited Speaker: Christiane Koch In cold collisions, where only a few partial waves contribute to the scattering dynamics, the wave nature of matter emerges, becoming observable in e.g. diffraction patterns, interference effects, or scattering resonances. The latter help build an intuitive understanding of the collision process, due to the spatial localization of the resonance wavefunctions. For resonances that are localized behind the centrifugal barrier and thus in the reaction region, sharp peaks in the reaction rates are the characteristic signature. If, however, the localization occurs outside of the reaction region, mostly the elastic scattering is modified. This may occur due to above-barrier resonances, the quantum analogue of classical orbiting. Resonances of both types are found in the example of metastable helium colliding with deuterium molecules [1]. |
Wednesday, June 2, 2021 11:00AM - 11:30AM Live |
K02.00002: Exploring the slow intracluster vibrational relaxation kinetics with two-color, IR-IR photoexcitation of cryogenically cooled water clusters Invited Speaker: Mark A Johnson Because the OH stretching quantum is close to the dissociation energy, vibrational excitation of the cold (20K) Iodide-HOD anionic complex in the OH stretching region explores the dynamics of a barely bound microscopic system. Here we examine the behavior of these levels by following the vibrational spectra of the states prepared by excitation of specific transitions in the cold complex in a two-color, IR-IR double resonance experiment. These results address the extent of IVR in the levels close to dissociation as well as the character of levels based on the OH stretching vibration that lie ~3000 wavenumbers above the onset of the dissociation continuum. Vibrational transitions from the OH(v=1) levels are observed to be quite sharp and are very long (tens of milliseconds) lived. This enables a quantitative exploration of the anharmonicities in the OH stretching degree of freedom far above the dissociation limit. We then discuss the application of these methods to follow the onset of spectral diffusion in the OH stretching spectrum of larger clusters with twenty water molecules. These clusters adopt pentagonal dodecahedron cage structures, and we find that the onset of spectral diffusion occurs at 100 K with large amplitude, rare events that occur with discrete jumps of about 300 wavenumbers. Surface melting is complete by 130 K or so. |
Wednesday, June 2, 2021 11:30AM - 12:00PM Live |
K02.00003: Molecule-molecule and atom-molecule collisions in an ultracold ensemble of bosonic 23Na39K molecules Invited Speaker: Silke Ospelkaus Understanding and controlling collisions in ultracold gases of all-ground state molecules is of great importance in particular in view of possible applications of the molecules for quantum-many-body physics and precision measurements. Here, we report the preparation of an ultracold gas of bosonic polar 23Na39K molecules in a specific hyperfine state of their rovibronic ground state. We analyze the two-body decay of a pure molecular sample and in various atom-molecule mixtures. In particular, we find an unexpectedly low two-body decay coefficient for collisions between molecules and 39K atoms in a selected hyperfine state [1]. Finally, we report about our recent studies of photoinduced-loss processes for the chemically stable 23Na39K molecules [2]. |
Wednesday, June 2, 2021 12:00PM - 12:30PM Live |
K02.00004: Universal relations for ultracold reactive molecules Invited Speaker: Qi Zhou Whereas ultracold molecules provide scientists with a powerful apparatus to study a vast range of new quantum phenomena and novel quantum states, a key issue about reaction-induced losses must be addressed. However, taking into account quantum many-body effects in chemical reactions imposes a grand challenge to physicists and chemists. In this talk, I will discuss a number of universal relations between the two-body losses of reactive molecules and quantum many-body correlations, which are valid for arbitrary particle numbers, arbitrary temperatures, and arbitrary interaction strengths. Such universal relations unfold the central role of contacts in quantum chemical reactions and open the door to an unexplored area intertwining quantum chemistry, atomic, molecular and optical physics, and condensed matter physics. |
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