Molecular Reorientation in Liquids and Gases

Abstract

In this paper two simple criteria for guessing the time‐dependent orientational distribution function from the experimentally measured dipolar autocorrelation function $〈{u}\text{(0)·}{u}\mathrm{(t)\; 〉}$ are examined. The first maximizes the information entropy of the distribution under the constraint imposed by the known $〈{u}\text{(0)·}{u}\mathrm{(t)\; 〉}$ , and the second minimizes the mean‐square difference between the distribution function and the equilibrium $\mathrm{(t\hspace{0.17em}\to \hspace{0.17em}\infty )}$ distribution under the same constraint. The accuracy of these criteria is tested on the results of computer studies of the rotational relaxation of diatomic liquids. The same general method is applied to the Van Hove self‐correlation function, and to the center‐of‐mass velocity transition probability.