High-resolution NMR spectroscopy of quadrupolar nuclei in solids: satellite-transition MAS with self-compensation for magic-angle misset.

Abstract

Several methods are available for obtaining high-resolution NMR spectra of half-integer spin quadrupolar nuclei, such as (11)B, (23)Na (I = (3)/(2)) and (17)O, (27)Al (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 (cos(-1)(1/ radical 3) = 54.736 degrees ) with respect to the magnetic field B(0) with an accuracy of better than +/-0.004 degrees, 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 degrees and yet retains a sensitivity comparable with MQMAS. This SCAM-STMAS experiment is demonstrated on RbNO(3) using (87)Rb (I = (3)/(2)) NMR and on kyanite (Al(2)SiO(5)) using (27)Al (I = (5)/(2)) NMR.