Exact line shapes in collision-induced absorption

Exact and simple expressions are obtained for the translational part of absorption spectra in rare gas mixtures using the following model. The induced electric dipole moment function is represented by a gaussian while for the intermolecular potential a hard core plus a soft repulsive tail is taken. The model generates nearly the same simple results as the phenomenological theory of Birnbaum and Cohen. The model is applied to the spectrum of a helium-argon mixture.