Theoretical Study for the Ground Electronic State of the Reaction OH + SO → H + SO2.

Abstract

The reaction OH + SO → H + SO2 plays an important role in the combustion of sulfur-containing fuels and environment. Its reaction profile resembles that of OH + CO → H + CO2, which presents a prototypical reaction with deep complexes forming. In this work, a new potential energy surface (PES) for the OH + SO → H + SO2 reaction is developed based on ca. 39 200 data points calculated at the level of explicitly correlated unrestricted coupled cluster method with singles, doubles, and perturbative triples excitations with the augmented correlation-consistent polarized triple zeta basis set (CCSD(T)-F12a/AVTZ). The PES is invariant with respect to the permutation of the two identical oxygen atoms, which is guaranteed by the permutation invariant polynomials as the input layer of the neural network. Using this PES, the quasi-classical trajectory method is employed to study the collision energy transfer between H and SO2 at the experimental translational energy of 59 kcal mol-1. The predicted large integral cross sections for trajectories producing SO2 with high vibrational energy, and populations of the SO2 vibrational energy are in good agreement with recent experiment and theory. Detailed analysis shows that there are two possible mechanisms, direct mechanism (without passing through HOSO or HSO2 well) and indirect one (passing through one or both wells). The latter dominates in producing SO2 with high vibrational energy.