摘要
HIGH-RESOLUTION solid state <sup>13</sup>C NMR spectroscopy has been a useful tool for the study of coalstructure.By the use of cross polarization（CP）,magic angle spinning（MAS）and protonhigh-power decoupling（HPD）techniques,high-resolution solid state <sup>13</sup>C NMR spectra ofcoals can be obtained and the coal aromaticity（f<sub>a</sub>）can be measured directly.Here aromaticityis defined as the ratio of aromatic carbon atoms to the total carbon atoms in coals.Twelve pa-
