Thermally excited multiplet states in coal macerals

The measurements of line intensity for macerals: exinite, vitrinite and ine rtinite, separated from bituminous coal (85.6 wt% C), were carried out in t he temperature range 100-300 K. The experimental correlation between the in tensities of the EPR/ESR components and temperature were fitted by theoreti cal functions for paramagnetic centres with thermally induced singlet-tripl et (S = 0 <-> = 1) and doublet-quadruplet (S = 1/2 <-> S = 3/2) excitations . It was found that the broad Lorentz line present in the EPR/ESR spectra o f exinite and vitrinite is responsible for the temperature dependence of in tegral line intensity which does not fulfil the Curie law. This proves the existence of thermally excited multiplet (triplet or quadruplet) states in coal. The energy of excitation J of both singlet-triplet and doublet-quadru plet states of paramagnetic centres is comparable with the energy kT. Param agnetic centres related to the broad Gauss and the narrow Lorentz line in e xinite and vitrinite and related to the two narrow Lorentz lines in inertin ite obey the Curie law.