Stereodynamics of rotationally inelastic scattering in cold He+HD collisions

TL;DR

This study uses quantum scattering calculations to analyze how shape resonances influence stereodynamics in cold He+HD collisions, revealing a more complex control mechanism than previously thought and identifying universal trends at low energies.

Contribution

It provides the first detailed quantum analysis showing the combined effect of multiple shape resonances on stereodynamics in He+HD collisions, challenging previous single-resonance assumptions.

Findings

Shape resonances from l=1 and l=2 partial waves control the stereodynamic outcome.

The control mechanism is more complex than the single l=2 partial wave suggested before.

A universal trend in stereodynamic preference is observed below 0.5 cm$^{-1}$.

Abstract

Stereodynamics of cold collisions has become a fertile ground for quantized studies of molecular collisions and control of the collision outcome. A benchmark process for stereodynamic control is rotational transition in He+HD collisions. This process was recently probed experimentally by Perreault et al. by examining quenching from $j=2$ to $j'=0$ state in the $v=1$ vibrational manifold. Here, through explicit quantum scattering calculations on a highly accurate ab initio interaction potential for He+H$_2$, we reveal how a combination of two shape resonances arising from $l=1$ and $l=2$ partial waves controls the stereodynamic outcome rather than a single $l=2$ partial wave attributed in the experiment. Further, for collision energies below 0.5 cm$^{-1}$, it is shown that stereodynamic preference for integral cross section follows a simple universal trend.