Electronically nonadiabatic transitions in a collinear H-2+H+ system: Quantum mechanical understanding and comparison with a trajectory surface hopping method

Electronically nonadiabatic transitions in a collinear H-2 + H+ system have been studied both quantum mechanically and with classical mechanics using a diatomics-in-molecules type potential energy surface fitted to recent ab initio data. The quantum dynamical calculations are carried out by employing a standard close-coupling method in hyperspherical coordinates and the quasiclassical trajectory calculations were carried out with a basic surface hopping method. Special emphasis is placed on qualitative analysis of the physical mechanisms of the electronically nonadiabatic transitions. To make such an analysis, the basic idea proposed by Nobusada et al. (K. Nobusada, O. I. Tolstikhin and H. Nakamura, J. Chem. Phys., 1998, 108, 8922) in the study of vibrationally nonadiabatic transitions is applied, and also the reaction dynamics is visualized in detail by using classical trajectories. It is found that the electronically nonadiabatic transition occurs in a rather narrow configuration space and its reactivity depends strongly on the initial vibrational state of H-2.