Modelling of vibrational Davydov splittings in alpha-T6 single crystal

The polarized infrared absorption spectra of alpha -sexithienyl single crystal show the Davydov splitting of some intramolecular ungerade phonons. They are analyzed into details considering the perturbation on the molecular force constants due to the solid state interactions within the unit cell. The proposed model allows to identify the effects of the pertubation within the molecular crystal and to estimate the new force constants of the unit cell.