Reaction rates when barriers fluctuate: A singular perturbation approach

We study the thermally activated surmounting of a potential barrier with a randomly fluctuating shape. For weak thermal and potential fluctuations analytical approximations based on path integral techniques are compared with accurate numerical results. Particular emphasis is put on the dependence of the potential fluctuation statistics upon their characteristic time scale (constant intensity versus constant variance). While many qualitative features are satisfactorily captured by the exponentially leading Arrhenius-type contribution to the rate, prefactor effects must be included for reliable quantitative predictions. (C) 1998 Elsevier Science B.V. All rights reserved.