Journal of the American Chemical Society, Vol.118, No.39, 9326-9332, 1996
Quantitative Multiple-Quantum Magic-Angle-Spinning NMR-Spectroscopy of Quadrupolar Nuclei in Solids
We describe a new approach for observation of multiple-quantum (MQ) NMR spectra of S=3/2 nuclei with magic-angle spinning (MAS). The new method employs the Rotation-induced Adiabatic Coherence Transfer (RIACT) that occurs between triple-quantum (3Q) and central-transition (1Q) coherences in S=3/2 systems. In contrast to currently available coherence-transfer techniques, RIACT is relatively insensitive to the magnitude of the quadrupole interaction for e(2)qQ/h less than or equal to MHz for both 3Q excitation and 3Q-to-1Q conversion. Thus, RIACT provides a means of extracting quantitative information about site populations from isotropic MQ NMR spectra. We illustrate the utility of the approach with Na-23 (S=3/2) MQ quantitative measurements of quadrupolar parameters, chemical shifts, and relative site populations for each of the crystallographically distinct sodium sites.
Keywords:HIGH-RESOLUTION NMR;MAGNETIC-RESONANCE;MAS-NMR;STATE NMR;SPIN-1/2 NUCLEI;ROTATIONAL-ECHO;DOUBLE-ROTOR;O-17 NMR;EXCITATION;TRANSITION