Temperature study of resonance intermolecular interaction in the aliphatic crystals using spectra of IR-absorption

In this work, on the example of odd-numbered normal paraffins and alpha-olefins we propose a mechanism which explains the temperature dependence of the magnitude of Davydov splitting Deltav(1,2) of the bands of scissoring and rocking vibrations of methylene chains of long-chain compounds with frequencies 1465 and 720 cm-1, respectively. This mechanism is connected with damping of the intramolecular vibrational excitons in crystals due to their interaction with orientational defects of the lattice which emerge as a result of excitation of librational-rotational degrees of freedom of organic molecules in the region of the phase transition of order - orientational disorder type. Good agreement was observed between theoretical and experimental results.