High-Resolution NMR Spectroscopy in Solids by Truly Magic-Angle Spinning

Right angles: In solid‐state magic‐angle spinning (MAS) NMR spectra, the line widths of carbonyl carbon atoms in polycrystalline cholesteryl acetate are found to be as narrow as 0.039 ppm if the magic angle is adjusted very accurately, that is, within ±0.004° (see picture). The line broadening observed for slightly miss‐set angles is mostly due to residual chemical shift anisotropy (CSA) interactions. Long spin‐echo life times up to ${{{\rm T}{{\prime \hfill \atop 2\hfill}}}$=3.6 s open the way to sophisticated NMR methods.