An experimental study of interaction-induced effects in the IR spectra of HI–Xe gas mixtures

Significant interaction-induced perturbation of the dipole moment function for the hydrogen iodide molecule is demonstrated in the absorption spectra of gas mixtures with xenon at elevated pressures. The integrated IR intensity of the (00 0 1) (00 0 0) HI fundamental stretch mode is found to increase by about 50% and the intensity of the first vibrational overtone (00 0 2) (00 0 0) mode to decrease by an order of magnitude in the spectra of binary Xe:HI van der Waals dimers, compared to the absorption intensities of free HI. Strong m-dependent variation with the perturber gas densities of the spectral line intensities for unbound molecules renders the Herman–Wallis analysis of the vibration–rotation coupling effect on the dipole moment function invalid for the high-density gas systems.