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-echoʹ STMAS experiment that yields pure absorptive lineshapes is presented and shown to be compatible with the `split-t1ʹ technique used in multiple-quantum (MQ) MAS NMR to reduce the duration of t2 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-termʹ broadening mechanisms on linewidths in `isotropicʹ STMAS spectra are discussed.