Application of a classical trajectory model to vibrational excitation in high-energyH++H2collisions

Abstract

The method of distribution among quantum states of exact classical energy transfer (the DECENT model) for vibrational excitation in molecular collisions, in which three-dimensional classical trajectories are used to evaluate the quantum vibrational transition probabilities, is applied to ${\mathrm{H}}^{+}$ + ${\mathrm{H}}_2$ and ${\mathrm{D}}^{+}$ + ${\mathrm{H}}_2$ collisions at relative kinetic energies between 35 and 1000 eV. We compare the results with the experimental data of Herrero and Doering. Taking into account the scattering-angle discrimination in the experimental measurements, we find good agreement with experiment for the shapes of the energy dependence of the calculated total cross sections for individual final vibrational states and for the cross-section ratios. The absolute magnitudes of the calculated vibrational-excitation cross sections at high energies are about a factor of 2 larger than the experimental values, probably because of electronically nonadiabatic behavior ignored in the calculation, but a systematic discrepancy exists at lower energies which cannot be completely reconciled with the available experimental information.