Stochastic dynamic models of curve crossing phenomena in condensed phases

Two stochastic dynamic models are used to study several aspects of curve crossing phenomena in dissipative systems. A surface hopping model is used to test the qualitative predictions of earlier theories. The simulation results agree well with the qualitative picture. Results are obtained for an alternate semiclassical model based on a vector spin representation which is derived via a variational principle. The vector model shows some differences in behavior as compared to the hopping model. In certain regimes the vector model shows chaotic behavior.