Article

Polyexponential kinetics of chemical reactions in condensed media within the quasiclassical approximation

The Journal of Chemical Physics (Impact Factor: 3.12). 01/1995; 102(4):1607-1618. DOI: 10.1063/1.468893

ABSTRACT Polyexponential kinetical behavior typical for condensed phase reactions in highly viscous media is studied on a simple example of one‐dimensional diffusion equation with a sink modeling a chemical conversion of reactants. The corresponding polyexponential regime is demonstrated to have a thorough analogy with the quasiclassical approximation of one‐dimensional quantum mechanics and a relevant approximation for the Green’s function is developed. The asymptotic short‐ and long‐time kinetics are examined at the analytical level. Contrary to the frozen medium approximation according to which the slow diffusion motion of the medium is entirely ignored, the present quasiclassical model is fit for a qualitative description of the total time interval covering the reaction events from the initial moment up to the ultimate steady‐state monoexponential evolution. The range of validity of the quasiclassical approach is discussed. Numerical tests expose some peculiarities of the present treatment for equilibrium and nonequilibrium initial distributions. The work presents a qualitative development of the theory of nonexponential kinetics pioneered by papers of Agmon and Hopfield, Sumi and Marcus, and Nadler and Marcus. © 1995 American Institute of Physics.

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