General kinetic models of activated processes in condensed phases

We continue our study of chemical relaxation processes J. Chem. Phys. 69, 2143 (1978) in considering a classical particle in a one-dimensional bistable potential coupled to a heat bath environment. We introduce a class of kinetic models which subsumes the special cases of the Rayleigh–Fokker–Planck, BGK, and Lorentz models. Using both analytical and numerical techniques we calculate the chemical relaxation rate of this system for different kinetic models and coupling strengths. We find that except in the Rayleigh limit, for a small range of couplings, transition state theory is quantitatively a poor approximation. Transition state theory is particularly inaccurate in the Lorentz limit, where it overestimates the rate by a factor of ten or more for all values of the coupling.