Dipolar-broadening of I=1/2-NMR spectra of solids

Abstract

The equations of motion of dipolar-coupled spins of I=1/2 placed on a rigid lattice are solved approximately in the high-temperature and high-field limit. The NMR-spectra predicted by this theory are in close agreement with both the theoretical spectral moments, up to the eighth in the case of a simple cubic lattice, and the extremely accurate experimental results which have been obtained in the case of CaF_2. The theory is compared with the recent NMR-experiment of Lefmann et al. on C-13 diamond. It predicts a double-peak splitting of the NMR-spectrum when the field is applied along [111], in accordance with the experiment, though the widths of the calculated resonance lines are smaller than observed.