Electric field gradient correlations in the quadrupolar relaxation rate in liquids

Publisher Website
Google Scholar
Abstract
A theory of the quadrupolar relaxation rate, RQ, in liquids is developed. In the process, the time dependence of the electric field gradient correlation function is investigated, and a formally exact result is obtained for the leading term in an expansion about t=0. An earlier theory, which has serious defects in this limit, is corrected, and the authors derive an expression for the correlation function which displays the correct physical behaviour. By means of this result, it is shown that when the field gradient is short-ranged, the quadrupolar relaxation rate is determined by rapid adjustments in the positions of the nearest neighbours of a relaxing nucleus. Calculations of RQ in liquid neon are in good agreement with experiment. When applied to liquid rubidium near the melting point, the relaxation rate obtained lies within the (wide) range of experimental uncertainty.