Cross-polarization dynamic-angle spinning nuclear magnetic resonance of quadrupolar nuclei

Abstract

The use of variable-angle spinning (VAS) with cross-polarization (CP) for quadrupolar nuclei has been evaluated both experimentally and theoretically. It is known that under normal spinning speeds the best VAS angle for performing CP is 0° (parallel to the magnetic field). We show that, with the use of dynamic-angle spinning (DAS) probes, CP may be done at 0° and detection in a one-dimensional VAS experiment may be performed at any angle in a zero-polarized VAS (ZPVAS) experiment. Finally, the combination of CP with k = 5 DAS (where the sample is spun first at 0° followed by 63·43°) provides both the highest resolution and the greatest sensitivity under normal conditions.