LINE-SHAPES IN CP/MAS NMR-SPECTRA OF HALF-INTEGER QUADRUPOLAR NUCLEI

Cross polarization (CP) from H-1 to quadrupolar nuclei with S = 3/2 has been carried out under magic-angle-spinning (MAS) conditions for powder samples of Na2B4O7.10H2O and H3BO3. The line shapes in the CP/MAS NMR spectra are different from those in the spectra measured with the single pulse sequence combined with H-1 dipolar decoupling. Furthermore, the line shapes are found to be dependent on the measuring conditions such as the pulse amplitude for the quadrupolar nuclei. The spin-locking experiments demonstrate that line shapes in CP/MAS NMR spectra are largely dependent on the spin-locking efficiency.