Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session M26: Nonadiabatic Dynamics in Cold and Ultracold Collisions and Reactions IIFocus Live
|
Hide Abstracts |
Sponsoring Units: DCP Chair: Brian Kendrick, Los Alamos Natl Lab |
Wednesday, March 17, 2021 11:30AM - 11:42AM Live |
M26.00001: On the stereodynamics of cold and ultracold H + D2 and D + HD chemical reactions Humberto da Silva Jr, Balakrishnan Naduvalath, Brian Kendrick Stereodynamic control of rotational quenching of vibrationally excited HD molecules, by means of cold inelastic collisions with H2, D2 and He, has recently been demonstrated by combining intra-beam technologies with Stark-induced adiabatic Raman passage techniques for the preparation of molecular states [1-2]. Control of the angular distribution of the scattered molecules in these processes has also been addressed in recent theoretical studies [3-5]. In this work we examine the stereodynamics of H + D2↔ D + HD chemical reactions in the cold and ultracold regimes with vibrational excitation of the molecules to the v=4 level. The trend in stereodynamic preference is analyzed in terms of polarization of the initial and final rotational angular momenta of the reactant and product molecules. |
Wednesday, March 17, 2021 11:42AM - 11:54AM Live |
M26.00002: Isotope effects in ultracold 3D non-adiabatic scattering of Ar–NO Alexander Teplukhin, Brian Kendrick The quantum scattering of Ar and NO in a 2Π electronic state involves two potential energy surfaces (PESs) accessed simultaneously during the collision. This non-adiabatic process is inherently quantum-mechanical and requires a full quantum description that includes the two coupled electronic states. Previously, we developed new three-dimensional potential energy surfaces (A′ and A″) and calculated the bound spectrum of the Ar–NO van der Waals complex. The surfaces were computed using the coupled-cluster CCSD(T) method in the complete basis set limit and were coupled by the spin-orbit interaction. In the present work, we model the “downhill” (exoergic) 2Π3/2 → 2Π1/2 inelastic collision of Ar and NO using these two new surfaces. The non-adiabatic process is modeled in the ultracold regime, which is the focus of recent experimental studies. The choice of exoergic pathway and ultracold regime is also computationally favorable. The inelastic cross sections are calculated and analyzed for different values of total angular momentum J and different isotope combinations of N and O. |
Wednesday, March 17, 2021 11:54AM - 12:06PM Live |
M26.00003: Differential cross sections for spin-orbit changing collisions of highly vibrationally excited NO near 1 K. Chandika Amarasinghe, Hongwei Li, Chatura Perera, Matthieu Besemer, Junxiang Zuo, Changjian Xie, Ad van der Avoird, Gerrit Groenenboom, Hua Guo, Jacek Klos, Arthur G Suits We have employed a “near-copropagating” beam configuration with a 4° intersection angle at the interaction region for scattering experiments which allows us to control the collision energy over a very a broad range, from around 1 K to far above room temperature. We have illustrated this for collisions of highly vibrationally excited NO molecules prepared in single quantum states using simulated emission pumping coupled with velocity map imaging detection. Here we present investigations of the collision-induced spin-orbit relaxation for collisions between vibrationally excited NO molecules (v=10) with Ar near 1 K utilizing the near-copropagating beams over a collision energy range from 1.5 cm-1 to 3.5 cm-1 . The excess energy available due to electronic deexcitation which is manifested in the NO recoil energy provides the platform to study collisions near cold limit while yielding a velocity map image from which the state-to-state DCSs can be extracted. The measured DCSs were compared with predicted DCSs from 2D and 3D quantum scattering calculations involving both multireference configuration interaction and couple cluster potential energy surfaces. The experimental results are found to present a challenge to current state-of-the-art electronic structure calculations. |
Wednesday, March 17, 2021 12:06PM - 12:42PM Live |
M26.00004: Quantum Control of Molecular Collisions Near 1 K Invited Speaker: Nandini Mukherjee The purpose of a scattering experiment is to probe molecular forces that drive chemistry at the most fundamental quantum level. However, the amount of information that can be extracted is often limited by the presence of a large number of initial states that blurs details of the interaction dynamics. To clearly understand the quantum dynamics of molecular processes it’s absolutely essential to eliminate averaging over the initial states. To control collisions at the quantum level we prepare a scattering sensitive population in a single orientational m quantum sublevel of a rovibrationally excited (v, j) molecular eigenstate using a coherent optical method called Stark-induced adiabatic Raman passage (SARP). To accomplish cold collisions, we developed a molecular beam technique that reduces the relative speed of the colliding partners by co-expanding them in a single supersonic beam. Using SARP prepared (v, j, m) quantum states of HD, and D2 we studied cold inelastic collisions in a supersonic beam co-expanded with its collision partners He, H2, and D2 molecules. The co-expansion brings the collision temperature down to a few Kelvin thereby reducing the number of input orbital states to l = 0, 1, 2. The small number of orbital states and a well-defined internal state prepared by SARP in the input channel has allowed us to develop a partial wave analysis for the scattering angular distribution. The partial wave analysis of the rotationally inelastic scattering has revealed strong stereodynamic preference and existence of a collisional resonance that momentarily binds the reactant molecules in a quasi-bound state within the centrifugal barrier of an orbital state. In my talk I will give an overview of the ongoing quantum state controlled cold collision research in our laboratory. |
Wednesday, March 17, 2021 12:42PM - 12:54PM Live |
M26.00005: Real time dynamics and He-induced electronic transitions in doped helium nanodroplets at 0.4 K Patricia Vindel Zandbergen, David bonhommeau, Louis Merle, Manuel Barranco, Fausto Cargnoni, MartÍ Pi, 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, March 17, 2021 12:54PM - 1:06PM Live |
M26.00006: Understanding the ‘Odd’ Behavior in Ozone Photodissociation Carolyn Gunthardt, Megan Aardema, Simon North
|
Wednesday, March 17, 2021 1:06PM - 1:42PM Live |
M26.00007: Real-time scattering of ultracold bi-alkali molecules: trap loss studies
Svetlana Kotochigova
Department of Physics of Temple University Invited Speaker: Svetlana Kotochigova Many bi-alkali molecules in their absolute ground state are chemically “stable” with respect to molecule-molecule collisions. Then the lifetime of molecules trapped in optical traps was expected to be several seconds limited by the surrounding vacuum. Recent experimental studies with these stable molecules in optical traps, however, observed a surprisingly short lifetime comparable to that of reactive molecules. An explanation of this phenomenon, suggested by Ref. [1], relies on the fact that the excited electronic state tetramer complexes become energetically accessible to resonant absorption of photons of the trapping lasers. This leads to uncontrolled spontaneous decay and loss of molecules from the trap. The initial theoretical treatment of losses was only based on a time-independent analyses of potential energy surfaces for the optimized geometry. The logical next step requires the time-dependent study of the collisional dynamics of molecules, where the electronic character of the collisional complex can significantly change over only a few-femtoseconds in synchrony with the motion of the nuclei. In this presentation, I describe our first efforts to model time-dependent quasi-classical scattering of two ultracold 23Na87Rb molecules in the presence of trapping light including both electronic ground and excited states. The quantum nature of the initial v = 0, J = 0 ro-vibrational ground state of the ultracold NaRb molecules and their external motion is simulated through quasi-classical sampling of the NaRb probability distribution. We illustrate collisional dynamics in the presence of an external trapping light with a wavelength of 1064 nm by calculating the first 10 ps of the collision for a variety of initial relative orientations of molecules. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700