AN APPROXIMATE SOLUTION OF THE FOKKER-PLANCK EQUATION FOR REACTIONS IN CONDENSED PHASES

The phase-space distribution function for reactive collisions in a condensed phase can be described by a Kramers-like Fokker-Planck equation. For the physical range of the relevant parameters we propose a realistic analytical approximation to the time-dependent distribution. The proposed solution can be motivated by physical consideration and/or by a variational principle and/or by the procedure of maximum entropy. A further useful approximation is to linearize the deterministic force about the mean trajectory. This limit which is not essential but very practical is similar to Heller's use of Gaussian wave-packets for the solution of the time-dependent Schrodinger equation.