Dipolar broadening ofI=1/2 NMR spectra of solids

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 ${\mathrm{CaF}}_2$. The theory is compared with the recent NMR experiment of Lefmann et al. on ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ 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.