NMR Theory of Gaseous CX3Y Molecules: High Frequency Effects of CF3H

Abstract

A general theory of nuclear spin relaxation is applied to gaseous CX3Y molecules and the effects of high frequency terms studied theoretically. Although there is experimental disagreement as to what the correct high density dependence is for CF3H, it is demonstrated that rotational high frequency contributions can have a dramatic effect on the density dependence of T1. Moreover, for 'reasonable' values of the linewidth, shift, and collisional overlap parameters, the density dependence is limited in variation when the parameters are changed, making it impossible to fit Courtney's initial large 'step'. A reasonable fit to Waugh's data and the higher density dependence of Courtney can be obtained with a low density T1/n value of 0.8 s/amagat. Only a dipolar intramolecular mechanism is considered for the high frequency contributions.