Cold collisions of rovibrationally excited D$_2$ molecules

TL;DR

This study presents quantum calculations of energy transfer in collisions of rovibrationally excited D$_2$ molecules, revealing resonance features that influence angular distributions, thus advancing understanding of molecular collision dynamics.

Contribution

It provides the first detailed quantum analysis of D$_2$+D$_2$ collisions involving vibrational excitation up to v=2 using a new high-accuracy potential energy surface.

Findings

Identification of key resonance features affecting angular distributions.

Quantum calculations align with experimental results by Zhou et al.

Enhanced understanding of rovibrational energy transfer mechanisms.

Abstract

The H$_2$+H$_2$ system has long been considered as a benchmark system for ro-vibrational energy transfer in bimolecular collisions. However, most studies thus far have focused on collisions involving H$_2$ molecules in the ground vibrational level or in the first excited vibrational state. While H$_2$+H$_2$/HD collisions have received wide attention due to the important role they play in astrophysics, D$_2$+D$_2$ collisions have received much less attention. Recently, Zhou et al. [Nat. Chem. 4 658 (2022)] examined stereodynamic aspects of rotational energy transfer in collisions of two aligned D$_2$ molecules prepared in the $v=2$ vibrational level and $j=2$ rotational level. Here, we report quantum calculations of rotational and vibrational energy transfer in collisions of two D$_2$ molecules prepared in vibrational levels up to $v=2$ and identify key resonance features that contribute to the angular distribution in the experimental results of Zhou et al. The quantum scattering calculations were performed in full dimensionality and using the rigid-rotor approximation using a recently-developed highly-accurate six-dimensional potential energy surface for the H$_4$ system that allows descriptions of collisions involving highly vibrationally excited H$_2$ and its isotopologues.