2000 Volume 79 Issue 3 Pages 222-230
In high-field NMR experiments of carbonaceous solids such as coal and pitch, the high-speed magic-angle spinning (MAS) method is a powerful technique for reducing the intensity of the spinning sidebands that disturbs the precise interpretation of the spectrum. However, the high-speed MAS produces two unfavorable problems. One is the decline in the rate of polarization transfer from 1H to 13C during the cross-polarization (CP), and another is the NMR signal intensity fluctuation in the dipolar-dephasing (DD) experiments. Therefore, the availability of high-speed MAS, variable amplitude (VA)-CP pulse sequence, and DD experiments with the delay times synchronized with sample spinning were examined in the high-field NMR of a carbonaceous sample. Consequently, it was confirmed that the high-field NMR spectroscopy is a useful technique for the structural characterization of carbonaceous solids as well as the low-field NMR.