Effect of the intensity of collisions on the orientational relaxation of spherical top molecules

The influence is investigated of the correlation of angular momenta before and after instantaneous impulsive collision on the course of the orientational relaxation of spherical top molecules. To do this, a Markovian master equation with a collision kernel by Keilson and Storer is solved semianalytically for orientational correlation functions of the first and second rank through the recursive relations. A particular case of the equation contains the J diffusion model and the rotational Fokker-Planck equation. The results of these calculations are compared with those of molecular dynamics simulations of the rough sphere fluid and good agreement is found.