Fine structure of Raman spectra in coals of different rank

• Fine structure of G and D bands in Raman spectra of various coals and anthracites is studied.
• Raman spectra of bituminous coals, subbituminous coals, and anthracites consist of five, four, and two or three Lorentzian subcomponents, respectively.
• The D2 subcomponent, probably responsible for imperfections in graphitic clusters, shows nearly linear Raman shift in the whole metamorphism range and can play role of the coal type indicator.
• Raman spectra of fat coal reveal one odd subcomponent just before underground outburst near 1190 cm− 1, which probably can serve as the outburst indicator.

Fine structure of G and D bands in Raman spectra of various coals is studied. It is shown that the spectra of all subbituminous and bituminous coals can be decomposed into 5 subcomponents while the spectra of anthracites are best fitted using 2, 3 or 4 subcomponents depending on coal rank. The analysis enabled to separate one subcomponent of D band, probably responsible for imperfections in graphitic clusters, which shows nearly linear shift in the whole metamorphism range and can play role of the coal type indicator. We have found that Raman spectra of the same fat coal reveal one more subcomponent just before underground outburst and only two subcomponents after the outburst. This subcomponent near 1190 cm− 1 is assignable to oscillations of methyl group bonds and probably can serve as the outburst indicator.