Shift-independent nuclear spin diffusion by slow magic-angle sample spinning for the exploration of solids

An improved spin-diffusion experiment for the exploration of local order in solids is described. By slow magic-angle sample spinning, it is possible to remove the dependence of the spin diffusion rate on the chemical shift difference between two interacting nuclear spins, while the informative chemical shielding anisotropy is fully retained. Slow magic-angle spinning shortens the time necessary for the spin system to reach the quasi-equilibrium state, and it allows for rapid spin diffusion also in the absence of heteronuclear dipolar interactions in contrast to static or rapidly spinning samples. The feasibility of the experiment is demonstrated for a sample of carbon-13 labelled amorphous atactic polystyrene.