Hydrodynamic analysis of non-hard-core interactions in the rotational relaxation of molecules; ESR data

Abstract

Molecular reorientation for symmetric tops is analyzed in terms of a stickiness factor (s) which measures, in terms of a hydrodynamic model, the lag of the fluid motion relative to that of the particle surface. For s = 1 and s = 0, the hydrodynamic problem is that of ’’stick’’ and ’’slip’’ boundary conditions for symmetric tops. For truly hydrodynamic situations, 0 ? s ⩽ 1, but since molecular reorientation is nonhydrodynamic, negative values of s are possible. Reorientational data obtained from ESR spectra, for vanadyl acetylacetonate in a number of solvents, including a series of alcohols, are analyzed in terms of the s factor.