Harmonic and anharmonic rate constants and transmission coefficients obtained from ab initio data

Recent ab initio information of Kraka and Dunning on the reaction OH+H-2-->H2O+H is used to construct a potential energy surface in the vicinity of the reaction path. The resultant energy surface reproduces the ab initio reactant and product properties and provides a good fit to the nb initio data in the interaction region. Anharmonic vibrational energy levels involving the bound degrees of freedom orthogonal to the reaction coordinate are obtained using perturbation theory through second order for cubic terms and first order for quartic terms, with resonance effects removed. These energy levels are used in the calculation of transmission coefficients and thermal rate constants over the temperature range from 200 to 2400 It. The results are compared with those obtained from harmonic vibrational energy levels. (C) 1997 American Institute of Physics.