Rotational Correlation Times for Quadrupolar Relaxation in Liquids

Abstract

The nuclear spin relaxation rate via quadrupolar interaction in liquids is related to the correlation time for rotational Brownian motion. Experimentally obtained values of the Cl35 relaxation times at various temperatures in chlorine-containing molecules are used to calculate the correlation times for these molecules. The values so obtained are an order of magnitude shorter than predicted by the familiar Stokes—Einstein relation. An expression for the rotational correlation time is derived using the liquid ``quasilattice'' model, assuming that relaxation takes place only when the molecule undergoes a ``jump'' to the top of the barrier at the cell boundary. Using this theory the correlation time for CCl4 is calculated and is in good agreement with the experimental value.