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Thermally excited multiplet states in coal macerals

Więckowski A. B.

Bulletin of the Polish Academy of Sciences. Chemistry

2000

Vol. 48, No. 4

385-395

The measurements of line intensity for macerals: exinite, vitrinite and inertinite, separated from bituminous coal (8.5.6 wt% C), were carried out in the temperature range 100-300 K. The experimental correlation between the intensities of the EPR/ESR components and temperature were fitted by theoretical functions for paramagnetic cen-tres with thermally induced singlet-triplet (S = 0 +--+ 5 = 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 of exinite and vitrinit.e is responsible for the temperature dependence of integral 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-trjplet and doublet-quadruplet states of paramagnetic centres is com-parable with the energy kT. Paramagnetic centres related to the broad Gauss and the narrow Lorentz line in exinite and vitrinite and related to the two narrow Lorentz lines in inertinite obey the Curie law.