OBTAINING LONG-TIME DYNAMICS IN THE SPECTROSCOPIC SPIN-BOSON MODEL VIA PATH INTEGRATION

The spectroscopic spin-boson model [J. Chem. Phys. 86, 995 (1987)] for quantum dynamics of nuclei on potential surfaces coupled by nonradiative effects is studied via path integral techniques. In particular, long time recurrence dynamics of the electronic absorption correlation function of a multimode system characterized by strong nonradiative coupling is computed by both direct enumeration of spin configurations and by a novel Monte Carlo method based on the extended adiabatic formulation of the spin-boson problem [J. Chem. Phys. 92, 4993 (1990)]. Besides providing a demonstration of the utility of path integration for studying detailed spectroscopic signatures of nuclear motion on excited electronic potential surfaces, it is argued that the basic technical procedures can be applied to a number of problems in which a quantum system is coupled to an environmental oscillator bath.