XE-131 NMR IN PROBING ELECTRIC-FIELD GRADIENTS IN THERMOTROPIC NEMATOGENS

131Xe NMR spectra of natural xenon gas dissolved in three nematic liquid crystals were recorded at various temperatures. The spectra in the nematic phases of the liquid crystals display quadrupole couplings of 162 to 495 kHz depending upon liquid crystal and temperature. The coupling arises from the interaction of the 131Xe nuclear quadrupole moment with the average electric field gradient at the nucleus. The external electric field gradient introduced earlier in the literature to explain the orientation and solvent dependence of the deuteron quadrupole couplings in methane and molecular hydrogen in liquid crystals does not alone explain the observed results, but at least two, and most probably more, different contributions must be considered. © 1990.