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 theoretically. 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 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-degrees followed by 63.43-degrees) provides both the highest resolution and the greatest sensitivity under normal conditions.