HYDROGEN TUNNELING IN CONDENSED MEDIA

A microscopic description for reactions in condensed media involving hydrogen tunneling, valid over a large temperature range, is presented. The tunneling system, represented by a pseudospin (S = 1/2), reaches equilibrium when coupled to its environment, modeled by a collection of harmonic oscillators that behave like a heat bath. The environment includes both modes of the lattice (or solvent) and those molecular vibrations which play an active role in the tunneling process. Analytical expressions for the reaction rate are given in various regimes.