Spin diffusion in resolved solid-state NMR spectra

Spectral spin diffusion in resolved solid-state NMR spectra is analyzed for various types of systems, including dipolar coupled spin-(1/2) systems in the presence of extraneous spins, and systems of quadrupolar spins with and without an additional dipolar reservoir. Diffusion of Zeeman and quadrupolar order via single-quantum and double-quantum spin-diffusion mechanisms is considered. Special attention is paid to the frequency offset dependence of the spin-diffusion rate. The theoretical predictions are verified by spin-diffusion measurements using two-dimensional spectroscopy techniques for ¹³C deuterium, and ¹⁴N resonance in single crystals.