Transverse Nuclear Spin Relaxation in Nematic Liquid Crystals. Angular Dependence of the Relaxation Rate in Pulsed Experiments

The theory underlying the slow-motional description of transverse relaxation in 2H-NMR pulsed experiments, sensitive to order director fluctuations in nematic liquid crystals, is outlined in a comprehensive way in order to highlight the physical parameters which enter the expressions elsewhere derived, to stress the limits of their applicability, and to address those experimental situations which may be more (or less) appealing from the point of view of the extent of information achievable from the analysis of the data. A comparison between fast-motional and slow-motional results is made here, for the first time, in relation to measures performed on samples aligned by the magnetic field.