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From the symmetry properties of spin interactions, one can design sample rotation techniques for averaging in solids. For the second-order quadmpole effect, this leads to double rotation (DOR), rotating the sample simultaneously about a specific pair of axes. Characteristics of DOR, such as spinning sidebands, are discussed, and representative applications are displayed.

An overview of dipolar-chemical shift spectroscopy is presented with emphasis on recent developments to improve sensitivity, enhance information content, and simplify the spectra. Three new experiments are examined. First, a simplified experiment which is not synchronized with the sample rotation is shown to yield the same 2D spectra as previous methods, but with higher signal intensities. Second, an experiment is demonstrated to enhance dipolar sideband intensities, allowing the measurement of weaker couplings at spinning speeds which would otherwise yield vanishingly small sidebands in the dipolar dimension. Lastly, a mechanical technique involving the changing of the spinning speed between the evolution and detection periods of the dipolar chemical shift experiment is shown to yield a dramatic compression of the information in the two-dimensional landscape. The signals obtained are calculated using a versatile formalism which comprises a basis for comparison of the results of different experiments.