Vibrational Quenching of CN- in Collisions with He and Ar

TL;DR

This study computes vibrational quenching cross sections and rate constants for CN- ions colliding with He and Ar, revealing very small rates relevant for astrochemistry and ion trap physics.

Contribution

It provides the first ab initio calculations of low-energy vibrationally inelastic collisions for CN- with neutral atoms using new potential energy surfaces.

Findings

Cross sections and rate constants are smaller than similar systems.

Results are relevant for molecular cooling and astrochemical models.

Implications for the dynamics of ion-neutral collisions are discussed.

Abstract

The vibrational quenching cross sections and corresponding low-temperature rate constants for the v = 1 and v = 2 states of CN- colliding with He and Ar atoms have been computed ab initio using new three dimensional potential energy surfaces. Little work has so far been carried out on low-energy vibrationally inelastic collisions for anions with neutral atoms. The cross sections and rates calculated at energies and temperatures relevant for both ion traps and astrochemical modelling, are found by the present calculations to be even smaller than those of the similar C2- /He and C2-/Ar systems which are in turn of the order of those existing for the collisions involving neutral diatom-atom systems. The implications of our finding in the present case rather small computed rate constants are discussed for their possible role in the dynamics of molecular cooling and in the evolution of astrochemical modelling networks.