Modeling of band shapes in the low-temperature molecular liquid spectra affected by resonance dipole-dipole interaction

The band shape theory of the vibrational transitions accompanied by an excitation of a strongly IR-active fundamental is elaborated for low-temperature molecular liquids with an account for strong intermolecular resonance dipole-dipole interactions. The developed model of a liquid uses the regular (fcc structure) crystal whose structure is then destroyed by introducing random, normally distributed displacements of particle positions, by assigning arbitrary molecular orientations as well as a varied number of randomly distributed vacancies. This model was applied to several molecular liquids (CF4,SiF4,SF6,CF3Cl,andCF3Br), those having triply degenerate modes were studied more in detail.