DYNAMICS ON POTENTIAL-ENERGY SURFACES WITH A CONICAL INTERSECTION - ADIABATIC, INTERMEDIATE, AND DIABATIC BEHAVIOR

The nuclear dynamics on potential energy surfaces which are strongly vibronically coupled through a conical intersection is investigated by exact (numerical) integration of the time-dependent Schrödinger equation. Results for realistic model systems including three nuclear degrees of freedom are presented: C2H4+, pyrazine and NO2. It was found previously for C2H4+ that the wave packet moves after an initial decay mainly on the lower adiabatic surface. This observation could be confirmed also for pyrazine and NO2. By varying the coupling strength λ also other types of behavior could be identified. A transition from adiabatic via intermediate to a diabatic nature of the system dynamics is found upon decreasing λ. Population of diabatic and adiabatic states in the long time limit are calculated by classical phase-space statistics. Analytic relations between the population of the diabatic states and the dynamical observables, coordinates and momenta, are derived. They allow for a deeper understanding of their long time limits. © 1990 American Institute of Physics.