Semiclassical wave packet dynamics in nonadiabatic processes: The conical intersection between the X̃ and à states OF C 2H 4+

Abstract

Autocorrelation and probability functions are calculated by semiclassical wave packet dynamics for the nuclear evolution of C 2H 4 + in its à state, connected with the X̃ state via conical intersection. Three distinct choices of potential energy surfaces were made: the canonic diabatic surface H 22, as defined by Köppel, the adiabatic surface E 2 and the Nikitin diabatic one H 22. The wave packet is expanded in a Gaussian basis set restricted to 40 functions. The influence of the initial Gaussian width as well as the influence of freezing this width or not is studied. Taking into account the fact that the basis set is very small, one can conclude that the results are in acceptable qualitative agreement with those obtained by Köppel. The apparent discrepancy between the canonic diabatic autocorrelation function and the exact one could be explained by the existence of a dynamical condition for the choice of the diabatic potential energy surface. In the case of C 2H 4 + (Ã), the behavior during the relaxation cannot be considered as essentially diabatic or adiabatic: it is intermediate.