On nonadiabatic effects in H−+H2 collisions

Nonadiabatic couplings between the low-lying singlet states of H3− are calculated by means of the diatomics-in-molecule method. The couplings between the ground state and the first excited singlet state are described in detail as being the most important for H−+H2 collisional processes. The nonadiabatic regions, including the simultaneously intersecting four seams of conical intersection, are specified in the three-dimensional space. It is shown that the nonadiabatic couplings influence remarkably the dynamics of all collisional processes in H−+H2 collisions. In particular, it is shown that the nonadiabatic transition mechanism dominates over the direct one for the electron detachment process. The electron detachment probabilities in collinear H−+H2(v) collisions are calculated by means of the classical trajectory method combined with the Landau–Zener model for nonadiabatic transitions for different initial vibrational quantum numbers v.