Molecular Relaxation in a Fluctuating Environment

Abstract

This paper relates the symmetric and asymmetric correlation-time distributions found in various relaxation experiments to one another, and to the single correlation time. The reorientation probabilities of the individual molecules are taken as functions of an environmental parameter, loosely termed the ``free volume,'' which is presumed to fluctuate with time. This treatment leads to a symmetric correlation-time distribution when the rate of ``free-volume'' fluctuation is much less than the various rates of molecular reorientation; an asymmetric distribution when these rates are comparable; and a single correlation time when the rate of fluctuation is much larger than the rates of reorientation.