On the Landau–Zener approach to nonadiabatic transitions for a vertical conical intersection

A Landau–Zener approach for nonadiabatic transitions in a vertical double cone conical intersection (CI) system due to Alijah and Nikitin [A. Alijah, E.E. Nikitin, Mol. Phys. 96 (1999) 1399] is pursued in terms of a rate constant perspective. Comparison of model results with those of surface hopping trajectory calculations shows that an approximate rate description for the upper cone population decay gives a reasonable global account of the nonadiabatic dynamics, especially when averages over a distribution of initial conditions is considered. Some limited results are also presented for the more general case of a tilted CI, and it is shown that concepts useful for the vertical CI also prove useful for this more complex situation.