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In solid-state NMR spectroscopy, magic-angle spinning is a technique routinely used to produce better resolution NMR spectra. MAS NMR consists in spinning the sample at the magic angle θm with respect to the direction of the magnetic field.
Three main interactions responsible in solid state NMR often lead to very broad and featureless NMR lines. However, these three interactions in solids are orientation-dependent and can be averaged to some extent by MAS:
In solution-state NMR, most of these interactions are averaged out because of the rapid time-averaged molecular motion that occurs due to the thermal energy.
The physical spinning of the sample is achieved via an impulse air turbine mechanism, where the sample tube is lifted with a bearing compressed gas to remove friction, and then spun with a drive gas. Sample tubes are hollow cylinders coming in a variety of outer diameters ranging from 0.70 to 7 mm, mounted with a turbine cap. The rotors are typically made from zirconium oxide, although other ceramic materials or polymers , polyoxymethylene ] can be found. Removable caps close the ends of the sample tube. The are made from a range of materials typically Kel-F, Vespel, or zirconia and boron nitride for an extended temperature range.