Journal of Physical Chemistry B, Vol.101, No.16, 3240-3249, 1997
Cross-Polarization from Quadrupolar Nuclei to Silicon Using Low-Radio-Frequency Amplitudes During Magic-Angle-Spinning
The dynamics of cross-polarization from the central transition of a quadrupolar nucleus (Al-27 or Na-23) to a spin-1/2 nucleus (Si-29) during magic-angle spinning and using low-radio-frequency Geld strengths are analyzed for the mineral low albite. Under these conditions additional complications in the spin-lock behavior of the quadrupolar nucleus and in the cross-polarization process were found experimentally and are examined in detail. A step-by-step procedure for optimizing cross-polarization from the central transition of a quadrupolar nucleus to a spin-1/2 nucleus is described. Significant enhancement of Si-29 NMR sensitivity and several applications are demonstrated.
Keywords:PROTON-ENHANCED NMR;SOLID-STATE NMR;MAGNETIC-RESONANCE;CORRELATION SPECTROSCOPY;COHERENCE TRANSFER;ROTATING SOLIDS;LOW ALBITE;MAS;SILICATES;LOCKING