SINGLE-RESONANCE AND DOUBLE-RESONANCE EXPERIMENTS OF QUADRUPOLAR NUCLEI IN SOLIDS USING SENSITIVITY ENHANCEMENT OF THE CENTRAL TRANSITION

Population enhancement for NMR of the central transition of quadrupolar nuclei in solids is performed by using adiabatic radiofrequency sweeps of the satellite transitions. Single-resonance experiments are reported for O-17, Na-23, Al-27, and Nb-93 nuclei in powders of Al-2,O-3, NaNbO3, and LiNbO3, and in Pyrex glass. Experimental techniques using single-coil probe circuits capable of both wideband frequency sweeps and narrowband detection are presented. The combination of population enhancement with cross polarization from Al-27 to O-17 in alpha-Al2O3 (corundum) powder is demonstrated. The sensitivity-enhancement technique is robust, with no critical parameters. (C) 1994 Academic Press, Inc.