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Proceedings Paper

Spectral effects of intermolecular interaction and phase transitions in pure n-paraffin crystals
Author(s): Galyna O. Puchkovska; V. D. Danchuk; A. P. Kravchuk; Jan I. Kukielski
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Paper Abstract

In JR spectra for region of phase transition "order-orientation disorder" is observed the temperature dependence of the Davydov splitting value for in-phase CH2 rocking vibrations of pure crystalline n-paraffins CnH2n+2(n=19, 21, 23, 30, 32). Within the frameworks of crystal thermal expansion model the Davydov splitting value of vibration frequencies for pure n-paraffins weakly depends on temperature in all temperature range of crystalline phase existence. A statistic and dynamic model is proposed, which provides adequate description of the observed effect. Jn the framework of this model, the damping of vibrational excitons on orientational defects of different nature takes place. Genesis of such defects is connected with excitation of librational and rotational molecular degrees of freedom at the crystal transitions into high-temperature orthorhombic and hexagonal crystalline states. Theoretical analysis of the effect of resonance dynamical intermolecular interaction on the spectra of intramolecular vibrations of the crystals was performed in terms of stochastic equations with account of phase transitions. Computer simulation of such dependence was performed for pure n-paraffin compounds. Good agreement between the experimental and computer simulation results was obtained.

Paper Details

Date Published: 20 July 2004
PDF: 7 pages
Proc. SPIE 5507, XVI International Conference on Spectroscopy of Molecules and Crystals, (20 July 2004); doi: 10.1117/12.569835
Show Author Affiliations
Galyna O. Puchkovska, Institute of Physics (Ukraine)
V. D. Danchuk, National Transport Univ. (Ukraine)
A. P. Kravchuk, National Transport Univ. (Ukraine)
Jan I. Kukielski, Univ. of Gdansk (Poland)

Published in SPIE Proceedings Vol. 5507:
XVI International Conference on Spectroscopy of Molecules and Crystals
Galyna O. Puchkovska; Tatiana A. Gavrilko; Olexandr I. Lizengevich, Editor(s)

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