CROSS-POLARIZATION DYNAMIC-ANGLE SPINNING NUCLEAR-MAGNETIC-RESONANCE OF QUADRUPOLAR NUCLEI

The use of variable-angle spinning (VAS) with cross-polarization (CP) for quadrupolar nuclei has been evaluated both experimentally and theo retically. It is known that under normal spinning speeds the best VAS angle for performing CP is 0-degrees (parallel to the magnetic field). We show that, with the use of dynamic-angle spinning (DAS) probes, CP may be done at 0-degrees and detection in a one-dimensional VAS exper iment may be performed at any angle in a zero-polarized VAS (ZPVAS) ex periment. Finally, the combination of CP with k = 5 DAS (where the sam ple is spun first at 0-degrees followed by 63.43-degrees) provides bot h the highest resolution and the greatest sensitivity under normal con ditions.