Phenomenological model for reaction kinetics coupled to a relaxing environment

Reasoning from the correlation between the height of the reaction barrier and the energy depth of substates attributed to different configurations of the reactant surroundings, the phenomenological approach to the rate processes in complex media has been proposed. The approach allows the formulation of the model based exclusively on the energetic consideration of the rate process rather than on the introduction of a particular configurational coordinate. This enables us to make conclusions concerning the most general features of rate processes in complex systems. In particular, we have identified three kinetic phases typical for chemical reactions proceeding in the complex molecular environment, including polychromatic (inhomogeneous), dispersive, and homogeneous phases. The expressions for the temporal behavior of the survival probability in each of these phases have been derived and compared with the empirical stretched exponential law. The temperature and scaling properties of survival probability has also been discussed. (C) 1997 Elsevier Science B.V.