ABSTRACT
Nuclear Magnetic Resonance (NMR) has long been a useful tool for physicists and chemists of all types. Until about 1970, NMR in solids was characterized by broad lines and poor sensitivity with the consequence that most studies involved the analysis of relaxation times and second moments to obtain essentially physical information. The advent of commercial spectrometers capable of routine high resolution solid state NMR has resulted in a proliferation of publications in the field. Hahn and Maxwell first used NMR to measure chemical exchange processes in liquids. Molecular motion may affect MAS spectra through interactions with the chemical shift anisotropy. Qualitatively, magic angle sample spinning is a coherent means of averaging the chemical shift tensor to its isotropic value and incoherent molecular motions serve to destroy that averaging.
