Key role of spin–orbit effects in the relaxation of CO2(010) by thermal collisions with O(3Pj)

Abstract

The quenching of CO2(010) by thermal collisions with ground-state atomic oxygen is a crucial process in determining the cooling rates of the thermospheres of Earth, Venus and Mars and then to predict changes due to the increase of this green-house gas. One of the questions raised by the experiments and aeronomical observations is with regard to the physical origin of the non-Landau–Teller and negligible temperature dependence of the vibrational relaxation rate at the temperatures existing in the thermospheres (150K≤T≥550 K). In this context, we extend our previous work on quantum scattering calculations performed on high-quality ab initio potential energy surfaces (PESs) [M. P. de Lara-Castells, Marta I. Hernández, G. Delgado-Barrio, P. Villarreal, and M. López-Puertas, J. Chem. Phys. 124, 164302 (2006)]. and report translational-energy averaged quenching probabilities for the previously reported C2 v PES as well as for additional orientational approaches of the oxygen atom. Our results reveal the spin–orbit couplings to be responsible for the temperature dependence of the quenching rate estimated from the analysis of upper atmospheric data. In addition, we analyse the effect of the PESs' anisotropy on the quenching process.