A wavepacket - Path integral method for curve-crossing problems: Application to resonance Raman spectra and photodissociation cross sections

A multidimensional Gaussian wavepacket dynamics - path integral method (GWD-PI) is utilized to study time evolution on two nonadiabatically coupled anharmonic potential energy surfaces. The proposed technique relies on single surface propagations in which the nuclear coordinate wavepacket hops from one potential surface to the other at selected times. Appropriate sequences of hopping times are considered and the output wavepackets associated with each sequence are summed coherently. Good agreement is obtained between GWD-PI and exact quantum dynamics for a two-dimensional model of photodissociation, even in the case of strong and spatially dependent nonadiabatic coupling.