Over his long and illustrious career, Bill Hase was always fascinated by gas-condensed phase collisions under highly non-equilibrium conditions, in particular how/if the essential dynamics could captured by detailed molecular dynamics calculations. This talk will address progress in quantum state resolved molecular collision and chemical reaction dynamics at the gas-liquid, gas-self assembled monolayer (SAM), and gas-liquid microjet interface, specifically highlighting the comparison between molecular dynamics theory and experiment that Bill loved so well. As one of several examples (time permitting), supersonically cooled deuterium chloride (10K, DCl (J = 0,1)) has been scattered from gas-liquid interfaces under thermal (Einc = 1.5(1) kcal/mol) and hyperthermal (Einc = 11.5(5) kcal/mol) conditions for prototypical liquids (PFPE, squalane and glycerol), with the final DCl quantum state probed via narrowband IR laser absorption methods to achieve rotational (J) and transverse Doppler (vy) resolution. We interpret our results in terms of a simple kinematic “lever arm” collision model, by which the angle of the DCl striking the surface influences the torque delivered by changing the effective lever arm and thereby enhancing or diminishing rotational excitation. We extend this simple model to more realistic gas-liquid interfaces with surface roughness due to thermally activated capillary waves, which predicts a surprisingly Boltzmann-like distribution of final quantum states characteristic of a rotational “temperature” and in agreement with many previous gas-liquid scattering studies with internal quantum state resolution.

Quantum-state-resolved molecular dynamics at gas-liquid, gas-SAM, and gas-liquid microjet interfaces: A “bipartisan” opportunity for theory and experiment

ACS Spring Meeting 2021

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