Collision-Induced Rotational Excitation of CO2 by N(4S) Atoms: A New Ab Initio Potential Energy Surface and Scattering Calculations.

Abstract

Collisional excitations of CO2 molecules are significant to fully understand the physical and chemical processes of astrophysical and atmospheric environments. Rotational excitations of CO2 molecules induced by N(4S) atoms have been studied for the first time. First, we have computed a new highly accurate ab initio potential energy surface (PES) of a CO2-N(4S) van der Waals complex. The PES has been obtained by employing the partially spin-restricted coupled cluster with open-shell single, double, and perturbative triple excitation method with aug-cc-pVQZ basis sets. The full close-coupling calculations have been performed to compute cross sections for kinetic energies up to 800 cm-1. For all of the excitations, rotational cross sections exhibit an overall decrease with the increase of the energy gaps. Rate coefficients are calculated by averaging the cross sections over a Maxwell-Boltzmann distribution for temperatures ranging from 1 to 150 K. The trends in rate coefficients are in good agreement with those of similar collision systems. The decrease in energy gaps and the increase in temperature are the key factors to enhance the rate coefficients of CO2 excitation. Our study will be useful for accurately establishing the atmospheric model of terrestrial planets and determining the abundance of CO2 and N(4S) in space.