MULTIDIMENSIONAL GENERALIZATION OF THE POLLAK-GRABERT-HANGGI TURNOVERTHEORY FOR ACTIVATED RATE-PROCESSES

The turnover theory for activated rate processes, is extended to multi dimensional systems. The theory derived in this paper accounts for the competition between intramolecular and intermolecular relaxation. The extent of chaotic motion of the system modes directly affects the rat e of energy diffusion in the system. The more chaos, the faster the en ergy diffusion and the larger the rate. The dependence of the rate on the intramolecular coupling strength is well accounted for. The theory is applied to a model two-dimensional system studied previously by St raub and Berne [J. Chem. Phys. 85, 2999 (1986)]. The theory, which is the multidimensional generalization of the one-dimensional Pollak, Gra bert, and Hanggi (PGH) turnover theory [J. Chem. Phys. 91, 4073 (1989) ] accounts well for the rate even in the case of extreme anisotropic f riction. The theory is cast in terms of the collective normal modes of the system and the bath and is thus applicable also to memory frictio n. (C) 1997 American Institute of Physics.