Collision-induced line shapes calculated with a hard sphere model

The induced-dipole autocorrelation functions for an exponential dipole and for a quadrupole-induced dipole are computed for a hard sphere potential. The first function is compared to collision-induced absorption results for rare gas mixtures. The shortcomings of the hard sphere model for the description of these short-ranged phenomena are considered. The second function is used to fit the experimental H₂-Xe rotational spectrum. Good agreement between the experimental and the calculated spectrum is obtained. It is concluded that the hard sphere model provides a good description of the longer ranged quadrupole-induced spectra.