Multi-Component EPR Spectra of Coals with Different Carbon Content
B. Pilawaa, A.B. Więckowskib, R. Pietrzakc and H. Wachowskac
aInstitute of Coal Chemistry, Polish Academy of Sciences, Sowińskiego 5, 44-121 Gliwice, Poland
bDivision of Magnetic Resonance Spectroscopy, Institute of Physics, Faculty of Physics& Astronomy, University of Zielona Góra, Szafrana 4a, 65-516 Zielona Góra, Poland
cLaboratory of Coal Chemistry and Technology, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland
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Received: 24 04 2005;
EPR spectra of lignite“Mequinenza” (Spain) (62.3 wt% C) and Polish orthocoking coal (87.8 wt% C) were compared. The spectra were superpositions of broad Gaussian, broad Lorentzian 1, and narrow Lorentzian 3 lines. Concentration of paramagnetic centers - mainly delocalizedπ electrons - responsible for narrow Lorentzian 3 lines increases with increase in carbon content in coal. Coal units with slow and fast spin-lattice relaxation processes exist in the two studied samples. Slow spin-lattice interactions occur in simple aromatic coal units with broad Gaussian and Lorentzian 1 lines. Fast spin-lattice relaxation processes are characteristic of large aromatic units with narrow Lorentzian 3 lines.
DOI: 10.12693/APhysPolA.108.403
PACS numbers:61.66.Hq, 76.30.Rn