SEMICLASSICAL THEORY OF ACTIVATED DIFFUSION

A semiclassical theory for the diffusion of a particle moving on a per iodic potential, coupled to a dissipative heat bath, is presented. The resulting expressions for the diffusion coefficient, mean squared pat h length, and hopping length distribution are valid for memory frictio n and provide a theory which goes uniformly from the underdamped to th e strongly damped limit. In the underdamped damped limit, quantum tunn eling and reflection cause the quantum diffusion coefficient to be low er than the classical, leading to an inverse isotope effect; the diffu sion of D atoms should be faster than the diffusion of H atoms.