EPR Evidence for Thermally Excited Triplet States in Exinite, Vitrinite and Inertinite Separated from Bituminous Coal

• Authors: G. Słowik , W. Wojtowicz , A. Więckowski
• Languages of publication: EN

Abstracts

EN

In this work we have made an electron spin resonance (EPR) study of macerals obtained from the lithotype clarain separated from Polish medium-rank coal (85.6 wt.% C). For three macerals:~exinite, vitrinite, and inertinite, the temperature dependence of intensity of EPR spectra in the temperature range of 100-373 K was investigated. The experimentally obtained EPR spectra of macerals were fitted by curves of the derivatives of the Gaussian and Lorentzian functions. The best fitting was obtained, when the experimental EPR spectra were assumed to be a superposition of three lines, for exinite and vitrinite - a broad Gaussian (G), a broad Lorentzian (L1) and a narrow Lorentzian (L3) line, but for inertinite of two lines - a narrow Lorentzian (L2) and a narrow Lorentzian (L3) line. The computer-assisted fitting has shown that each individual component line has similar values of resonance field, but different linewidths and amplitudes. The temperature dependence of line intensity I of the broad Gaussian (G) and narrow Lorentzian (L2 and L3) lines fulfils the Curie law in the form I=C/T or IT=C, whereas the broad Lorentzian (L1) line does not fulfil the Curie law. In the last case the temperature dependence of the Lorentzian (L1) component was fitted by the relation I=C/T+B/[T(3+exp(J/kT))] or IT=C+B/[3+exp(J/kT))], valid for thermally excited triplet states (S=1). For exinite and vitrinite the curves presenting the temperature dependence of the product IT versus temperature T were resolved into two curves, one for paramagnetic centres in the doublet state (S=1/2), and the other for paramagnetic centres in the thermally excited triplet state (S=1).

Keywords

EN

61.66.Hq; 76.30.Rn; 87.64.Hd

Discipline

• 76.30.Rn: Free radicals
• 61.66.Hq: Organic compounds

• Publisher: Institute of Physics, Polish Academy of Sciences
• Journal: Acta Physica Polonica A
• Year: 2005
• Volume: 108
• Issue: 1
• Pages: 171-176

Dates

published

2005-07

received

2005-04-24

Contributors

author

G. Słowik

• Institute of Physics, University of Zielona Góra, Prof. Z. Szafrana 4a, 65-516 Zielona Góra, Poland

author

W. Wojtowicz

• Institute of Physics, University of Zielona Góra, Prof. Z. Szafrana 4a, 65-516 Zielona Góra, Poland

author

A. Więckowski

• Institute of Physics, University of Zielona Góra, Prof. Z. Szafrana 4a, 65-516 Zielona Góra, Poland

References

• 1. S. Duber, A.B. Wieckowski, Fuel, 63, 1474, 1984
• 2. K.S. Rothenberger, R.F. Sprecher, S.M. Castellano, H.L. Retcofsky, in: Magnetic Resonance of Carbonaceous Solids, Eds. R.E. Botto, Y. Sanada, Advances in Chemistry Series, Vol. 229, American Chemical Society, Washington (DC) 1993, p. 581
• 3. R.B. Clarkson, Wei Wang, D.R. Brown, H.C. Crookham, R.L. Belford, in: Magnetic Resonance of Carbonaceous Solids, Eds. R.E. Botto, Y. Sanada, Advances in Chemistry Series, Vol. 229, American Chemical Society, Washington 1993, p. 507
• 4. B. Pilawa, A.B. Wieckowski, B. Trzebicka, Radiat. Phys. Chem., 45, 899, 1995
• 5. A.B. Wieckowski, B. Pilawa, L. Światkowska, W. Wojtowicz, G.P. Slowik, M. Lewandowski, J. Magn. Reson., 145, 62, 2000
• 6. A.B. Wieckowski, B. Pilawa, W. Wojtowicz, G.P. Slowik, H. Wachowska, Fuel, 80, 451, 2001
• 7. T.I. Smirnowa, A.I. Smirnow, R.B. Clarkson, R.L. Belford, J. Phys. Chem., 98, 2464, 1994
• 8. G.P. Slowik, A.B. Wieckowski, Appl. Magn. Reson., 24, 437, 2003
• 9. S. Schlick, M. Narayana, L. Kevan, Fuel, 62, 1250, 1983
• 10. W.E. Hatfield, in: Theory and Applications of Molecular Paramagnetism, Wiley, Boudreaux/Mulay 1976, ch. 7

Identifiers

DOI

10.12693/APhysPolA.108.171