Full-dimensional quantum scattering calculations of rovibrationally excited HD+HD collisions

TL;DR

This paper presents detailed quantum scattering calculations for HD+HD collisions, revealing resonant features and providing rate coefficients across a wide temperature range, aligning well with experimental data.

Contribution

It introduces full-dimensional quantum scattering calculations for HD+HD, identifying key resonances and anisotropic effects, and provides comprehensive rate coefficients from 0.1 K to 200 K.

Findings

Resonant features in low-energy cross sections linked to specific partial waves.

Agreement with experimental total cross sections and resonant behaviors.

Identification of a shape resonance around 2.5 K affecting rate coefficients.

Abstract

Full-dimensional quantum scattering calculations are reported for ro-vibrational transitions in HD+HD collisions using a highly accurate interaction potential for the H$_2$-H$_2$ system. Several near-resonant ro-vibrational transitions are identified that conserve the overall rotational angular momentum and nearly conserve the internal energy of the collision partners. Key anisotropic terms that drive the rotational transitions and angular momentum partial waves that contribute to low energy resonant features in the energy dependence of the cross sections are identified. The computed results are in agreement with total cross sections reported in previous experimental results, including resonant features in the energy dependence of the cross section. In particular, low-energy cross sections show a strong resonant feature associated with an $l=3$ partial wave in the incident channel. Rate coefficients for several inelastic rotational and ro-vibrational transitions are reported for temperatures ranging from $0.1$ K to $200$ K and they display a maximum between $1$ K-$10$ K reflecting the important contributions from the $l=3$ shape resonance that occurs around 2.5 K.