Effect of nuclear spin symmetry in cold and ultracold reactions: D + para/ortho-H$_2$

TL;DR

This study investigates how nuclear spin symmetry in H$_2$ molecules affects reaction dynamics and vibrational quenching of D collisions at cold and ultracold temperatures, revealing resonance structures influenced by nuclear spin states.

Contribution

It provides the first detailed analysis of nuclear spin symmetry effects on barrier dominated and barrierless reactions in ultracold conditions.

Findings

Resonant structures depend on nuclear spin states of H$_2$.

Nuclear spin symmetry influences partial wave contributions.

Implications for ultracold chemistry benchmarks.

Abstract

We report results for reaction and vibrational quenching of the collision D with para-H$_2$($v,j=0$) and ortho-H$_2$($v,j=1$) at cold and ultracold temperatures. We investigate the effect of nuclear spin symmetry for barrier dominated processes ($0\le v\le 4$) and for one barrierless case ($v=5$). We find resonant structures for energies in the range corresponding to 0.01--10 K, which depend on the nuclear spin of H$_2$, arising from contributions of specific partial waves. We discuss the implications on the results in this benchmark system for ultracold chemistry.