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

TL;DR

This paper develops an approximate theoretical model for I=1/2 NMR spectra in solids considering dipolar interactions, successfully matching spectral moments and experimental data, and predicting spectral features under specific field orientations.

Contribution

It introduces an approximate solution to the equations of motion for dipolar-coupled spins in solids, accurately predicting NMR spectral moments and experimental spectra, including specific field orientation effects.

Findings

Spectra match spectral moments up to eighth order for simple cubic lattice.

The theory agrees with experimental spectra of CaF2.

Predicts double-peak splitting in C-13 diamond under [111] field orientation.

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.