Two-dimensional satellite-transition MAS NMR of quadrupolar nuclei: shifted echoes, high-spin nuclei and resolution

Modifications to the satellite-transition magic angle spinning (STMAS) experiment for obtaining high-resolution NMR spectra of quadrupolar nuclei are discussed. A phase-modulated 'shifted-echo' STMAS experiment that yields pure absorptive lineshapes is presented and shown to be compatible with the 'split-t(1)' technique used in multiple-quantum (MQ) MAS NMR to reduce the duration of t(2) acquisition and avoid shearing the final two-dimensional spectrum. The application of STMAS to nuclei with spin greater than I = 3/2 is also considered. the dispersion of isotropic shifts achieved by STMAS and MQMAS are compared, and the effects of anisotropic 'cross-term' broadening mechanisms on linewidths in 'isotropic' STMAS spectra are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.