Nuclear magnetic resonance spectra of rapidly-rotated solids containing reorienting molecular groups

The effect is considered of macroscopic rotation of a solid about the magic axis on its nmr spectrum in those cases where the spectrum is already partially narrowed by microscopic nuclear motion within the solid. Two cases are distinguished; (a) in which rapid but restricted microscopic motion reduces the spectral width to a smaller plateau value, and (b) in which isotropic motion incompletely narrows the spectral width because it is insufficiently fast. In case (a) it is shown that macroscopic rotation can accomplish further substantial narrowing, and the limitations on the ultimate linewidth are discussed; in case (b) it is shown that macroscopic rotation at attainable speeds often has little effect.