Reaction dynamics of S(1D)+H2/D2 on a new ab initio potential surface

Abstract

A new ab initio potential energy surface is generated for the chemical reaction, S(1D)+H2. The quantum chemistry calculations were carried out at the multi-reference configuration interaction (MRCI) level with multi-configuration self-consistent field (MCSCF) reference wave functions. The 1A′, 2A′, 3A′, 1A″, and 2A″ singlet surfaces were computed on a uniform spatial grid of over 2000 points to simulate the full reaction pathway. The results indicate a barrierless insertion pathway along the T-shaped geometry and an 8 kcal/mol barrier to abstraction along the collinear geometry. The lowest surface was fit to a smooth analytical function form based on the reproducing kernel Hilbert space approach and a Carter–Murrell-type expansion. The dynamics of the S(1D)+H2/D2 reactions were simulated using the quasi-classical trajectory method. The results are generally consistent with an insertion mechanism mediated through capture dynamics in the entrance channel followed by the statistical decay of a long-lived complex. Comparison to recent molecular beam experiments shows agreement in the broad pattern of results but also exhibits significant differences in the more finely resolved quantities.