Rotational excitation of OCS by Ar: new potential energy surface, collisional cross sections and rate coefficients

Abstract

In the physical conditions of the troposphere, Carbonyl sulphide (16O12C32S) and Argon (Ar) are present. In the goal of studying the rate coefficients for rotational excitations of OCS with an abundant element in the troposphere, such as Ar, a new potential energy surface (PES) of OCS-Ar system over their ground electronic states: OCS ( $\mbox{X}^{1}\varSigma^{+}$ ) and Ar( ${}^{1}\mbox{S}_{u}$ ), has been investigated with the ab initio explicitly correlated Coupled Cluster including single, double and perturbative treatment of triple excitations (CCSD(T)-F12) level of theory, associated to the augmented correlation consistent valence triple zeta Aug-cc-pVTZ basis set. In this paper, the Coupled State approximate method “CS” was used in order to calculate inelastic cross-sections at energies up to $2000~\mbox{cm}^{-1}$ . The collisional rate coefficients derived from these rotational inelastic cross-sections were determined and discussed for kinetic temperature $T \leq 400~\mbox{K}$ and for OCS rotational levels $J \leq 20$ .