Molecular dynamics simulation of a rare gas liquid mixture has been used to investigate the connections of the collision induced absorption spectrum and the forces acting between liquid particles. We find that the force law and induced dipole moments determined for low density gases are incapable of producing collision induced absorption spectra which are in qualitative agreement with the experimentally observed low frequency part of the spectra for Ar–Ne mixtures. Qualitative agreement is obtained if the gas phase dipole is modified so that the zero of the dipole moment roughly matches the zero of the force between unlike species. This represents a substantial change in the gas phase dipole. The implications of these results are briefly discussed.