Abstract

Several methods are available for obtaining high-resolution NMR spectra of half-integer spin quadrupolar nuclei, such as ¹¹B, ²³Na (I = 3/2) and ¹⁷O, ²⁷Al (I = 5/2), in powdered solids. Satellite-transition magic-angle spinning (STMAS) uses only conventional magic-angle spinning (MAS) hardware and, it has been claimed, improves significantly upon the signal-to-noise ratio obtained with the widely adopted multiple-quantum MAS (MQMAS) experiment. The STMAS technique, however, requires that the sample rotation axis be set to the magic angle (54.736°) with respect to the magnetic field B₀ with an accuracy of better than ±0.004° and this stringent requirement has severely limited the use of the method. Here, we propose a novel version of STMAS that self-compensates for magic-angle missets of up to ±1.0° and yet retains a sensitivity comparable with MQMAS. This SCAM-STMAS experiment is demonstrated on RbNO₃ using ⁸⁷Rb (I = 3/2) NMR and on kyanite (Al₂SiO₅) using ²⁷Al (I = 5/2) NMR.