On the origin of the dynamical differences on the diatomics-in-molecules and spline-fitted a b i n i t i o surfaces for the He+H2+ reaction

The dynamic behavior of the He→H+2→HeH++H reaction has been examined on a DIM and a cubic spline fit to the ab initio surface values of Brown and Hayes. Examination of the total integrated reaction probability and the variation of vibration–translation energy transfer as a function of initial H+2 vibration phase on these two surfaces, as well as on two composite spline-fitted surfaces, indicates that the origin of the dynamical differences on the DIM and SAI surfaces for the He+H+2 reaction resides primarily in differences in shape of the inner repulsive wall. For this reaction, this region is shown to be the most important topological feature of the surface. Vibrational excitation probabilities on the two surfaces at energies below reaction threshold are also presented and compared with the results of Chapman and Hayes on the DIM surface. In spite of the influence of a well, the trajectories are, on the average, direct and short-lived on the SAI surface. In contrast, they are indirect and long-lived on the DIM surface.