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 H06: Collisions and Control with Atoms and MoleculesLive
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Chair: Paul Julienne, JQI |
Wednesday, June 2, 2021 8:00AM - 8:12AM Live |
H06.00001: Loss of ultracold RbCs molecules via optical excitation of long-lived two-body collision complexes Philip Gregory, Jacob Blackmore, Sarah L Bromley, Simon L Cornish We show that the lifetime of ultracold ground-state bosonic RbCs molecules in an optical trap is limited by fast optical excitation of long-lived two-body collision complexes. We partially suppress this loss mechanism by applying square-wave modulation to the trap intensity, such that the molecules spend 75% of each modulation cycle in the dark. By varying the modulation frequency, we show that the lifetime of the collision complex is 0.53(6) ms in the dark. These results are crucial for further understanding of ultracold molecular collisions, and for benchmarking theoretical models. |
Wednesday, June 2, 2021 8:12AM - 8:24AM Live |
H06.00002: Towards an optical tweezer array of individually trapped RbCs molecules Alex Guttridge, Ralph V Brooks, Stefan J Spence, Daniel Ruttley, Jeremy Hutson, Simon L Cornish The rich internal structure and intrinsic dipolar interactions possessed by polar molecules makes them a promising system for exploring quantum chemistry, quantum computation and quantum simulation. However, to fully realise their potential in these areas, single-site control and detection of molecules is desirable. Such control is natively realised using optical tweezer arrays to confine the molecules, which enables trapping and rearrangement of the particles to create arrays in flexible geometries. |
Wednesday, June 2, 2021 8:24AM - 8:36AM Live |
H06.00003: Probing open- and closed-channel p-wave Feshbach resonances Colin J Dale, Denise Ahmed-Braun, Kenneth G Jackson, Scott Smale, Ben A Olsen, Servaas Kokkelmans, Paul Julienne, Joseph H Thywissen We study a p-wave Feshbach resonance in potassium-40 with a combination of spectroscopic binding energy measurements, coupled-channels calculations, and a two-channel model [1]. Using both resonant association and spin-flip association, the binding energy of bound and quasi-bound dimers is measured across a five-gauss range. Our scattering model incorporates the ramping closed-channel state, weak dipole-dipole interactions, and a low-lying p-wave shape resonance in the open channel. The open-channel resonance affects low energy scattering and creates nonlinearity in the binding energy near threshold, which resolves an open question [2]. We explain why in the low-energy limit a divergent contribution to the scattering volume from dipole-dipole interactions violates the p-wave threshold law, and how we isolate the contribution of the short-range potentials to scattering. Our improved understanding of p-wave scattering near this resonance enables quantitative testing of predictions for low-dimensional odd-wave gases, and lays a basis for future few- and many-body p-wave experiments. |
Wednesday, June 2, 2021 8:36AM - 8:48AM Live |
H06.00004: Complete quantum coherent control of ultracold collisions Adrien Devolder, Paul Brumer, Timur Tscherbul Most current control methods for ultracold atomic and molecular collisions are based on static (dc) and time-varying (ac) external electromagnetic fields. Unfortunately, they suffer several caveats, like the absence of magnetic (or electric) dipole moments for some molecules, the practical laboratory dc fields, or the perturbation of high-precision experiments. |
Wednesday, June 2, 2021 8:48AM - 9:00AM Live |
H06.00005: Universal stereodynamics and electric field control of cold atom-molecule collisions Timur Tscherbul, Jacek Klos We use numerically exact quantum dynamics calculations to demonstrate universal stereoselectivity of cold atom-molecule collisions in an external electric field. We show that cold collisions of Ne atoms with OH molecules in their low-field-seeking f-states, whose dipole moments are oriented against the field direction, are much more likely to lead to inelastic scattering than those of molecules oriented along the field direction, causing nearly perfect steric asymmetry in the inelastic collision cross sections [1]. We identify the universal nature of this effect as due to the threshold suppression of inelastic scattering between the degenerate Stark M-sublevels of the high-field-seeking e-state, where M is the projection of the total angular momentum of the molecule on the field axis. Above the Lambda-doublet threshold, the stereodynamics of inelastic atom-molecule collisions can be tuned via electric-field-induced resonances, which enable effective control of Ne+OH scattering over the range of collision energies achievable in current merged beam experiments. |
Wednesday, June 2, 2021 9:00AM - 9:12AM Live |
H06.00006: Magnetic Moments of Lanthanide van der Waals Dimers John L Bohn, Lucie Augustovi\v{c}ov\'{a}, Joseph McCann Loosely bound van der Waals dimers of lanthanide atoms, as might be obtained in ultracold atom experiments, are investigated. These molecules are known to exhibit a degree of quantum chaos, due to the strong anisotropic mixing of their angular spin and rotation degrees of freedom. Within a model of these molecules, we identify different realms of this anisotropic mixing, depending on whether the spin, the rotation, or both, are significantly mixed by the anisotropy. These realms are in turn generally correlated with the resulting magnetic moments of the states, providing alternate probes of the chaos in these molecules. |
Wednesday, June 2, 2021 9:12AM - 9:24AM Live |
H06.00007: Stereodynamics of cold and ultracold rotationally inelastic collisions Masato Morita, Balakrishnan Naduvalath Stereodynamics of cold collisions has become a fertile ground for sensitive probe of molecular collisions and control of the collision outcome. A benchmark system for stereodynamic control of rotational transition is He + HD. This system was recently probed experimentally by Perreault et al. [1] by examining quenching from j = 2 to j'=0 state in the v = 1 vibrational manifold of HD by preparing the initial molecular orientation as a coherent superposition of mj states. Here we report explicit quantum calculations of rotational quenching of HD within the v=1 vibrational level by collisions with He for j=2 and 3 in the cold and ultracold regimes. In the cold regime near 1 K, the stereodynamics is controlled by the l=1 and l=2 partial waves [2,3]. While stereodynamic control is generally not effective in the ultracold regime due to the dominance of the incoming s-wave (l = 0 partial wave) we show strong mj and mj' dependence for both integral and differential cross cross sections in the ultracold regime [3]. |
Wednesday, June 2, 2021 9:24AM - 9:36AM Live |
H06.00008: Real time dynamics and He-induced electronic transitions in doped helium nanodroplets at 0.4 K Patricia Vindel Zandbergen, Nadine Halberstadt Real time dynamics of photo-excited metal atoms on the surface of superfluid 4He nanodroplets has revealed the possible existence electronic transitions induced by this unusual quantum, finite size “solvent “[1,2]. The results of approximated (Zero-Point Averaged Dynamics) dynamics [3,4] for the photodissociation of Ba+ from a 4He1000 droplet presented here will show and rationalize their existence. |
Wednesday, June 2, 2021 9:36AM - 9:48AM Live |
H06.00009: On the stereodynamics of cold and ultracold H + D2 and D + HD chemical reactions Humberto da Silva Jr, Brian K Kendrick, Balakrishnan Naduvalath Stereodynamic control of rotationally inelastic scattering of ro-vibrationally excited HD molecules in cold collisions with H2, D2, and He has been demonstrated recently by combining co-expansion of the colliding species in a molecular beam and Stark-induced adiabatic Raman Passage techniques for the preparation of molecular states. Control of the angular distribution of the scattered molecules in these processes has also been addressed theoretically for HD + H2, HCl + H2 and He + HD collisions. In this work we examine the stereodynamics of H + D2 ↔ D + HD chemical reactions with vibrational and rotational excitation of the reactants to the v = 2, 4 and j = 0-4 levels at collision energies ranging from 100 mK to 10 K. |
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