Magic angle spinning (MAS) is a solid-state nuclear magnetic resonance (NMR) technique used to enhance the resolution of NMR spectra. It is used extensively in the study of both inorganic and organic materials.
The MAS technique was first developed in the early 1970s by a team of scientists at Stanford University led by Richard Ernst. Since then, MAS has become an essential tool for the characterization of a wide variety of materials.
MAS involves spinning the sample at a very high speed (usually around 20,000 rpm) while the NMR experiment is being conducted. This creates a magic angle between the direction of the spins of the nuclei in the sample and the direction of the magnetic field.
The magic angle ensures that the spins of the nuclei do not experience any net magnetic field, which would otherwise cause them to precess and dephase. This results in a much sharper NMR signal and allows for the resolution of very small details in the spectra.
MAS is usually combined with another NMR technique called cross-polarization (CP), which further enhances the signal intensity. CP involves transfer of polarization from the thermal population of the spins to the spins of the nuclei of interest.
The combined MAS-CP technique is extremely powerful and has allowed for the characterization of a wide variety of materials, ranging from catalysts to biomolecules.
MAS-CP NMR spectroscopy has become an indispensable tool in the field of materials science and is used extensively in both research and industry.