Mode-Specific Quantum Dynamics Study of OH+H _2 S \rightarrow H _2 O+SH Reaction

The hydrogen abstraction reaction from H _2 S by OH is of key importance in understanding of the causes of acid rain, air pollution, and climate change. In this work, the reaction OH+H _2 S \rightarrow H _2 O+SH is investigated on a recently developed ab initio-based globally accurate potential energy surface by the time-dependent wave packet approach under a reduced-dimensional model. This reaction behaves like a barrier-less reaction at low collision energies and like an activated reaction with a well-defined barrier at high collision energies. Exciting either the symmetric or antisymmetric stretching mode of the molecule H _2 S enhances the reactivity more than exciting the bending mode, which is rationalized by the coupling strength of each normal mode with the reaction coordinate. In addition, the mode-specific rate constant shows a remarkable non-Arrhenius temperature dependence.