Infrared band shape and intensity studies on molecular motions and interactions in condensed phases. Part 2.—Effects of vibrational relaxation and collisional broadening on the spectra of ICl and IBr in benzene and cyclohexane

Abstract

The infrared spectra of ICl and IBr have been obtained as a function of concentration and temperature (200–350 K) over the range 20–500 cm^–1 in benzene and cyclohexane. The results have been interpreted in terms of the molecular dynamic processes and interactions occurring in the different solvents. It is shown that the ν(IBr) band profile is predominantly controlled by non-reorientational processes and that a collisional broadening model with some vibrational relaxation will satisfactorily explain the experimental correlation times in the liquid and solid phases. For ν(ICl) rotational diffusion probably also contributes to the band profile and this may be used to rationalise the difference in behaviour of these two molecules.