Translational Spectra Due to Collision-Induced Overlap Moments in Mixtures of He with CO₂, N₂, CH₄, and C₂H₆

Enhancement of the absorption, upon addition of He to CO₂, N₂, CH₄, and C₂H₆, has been observed in the frequency region 200–450 cm⁻¹. It is shown that in this frequency region absorption due to multipole moment induction is weak and particularly so because of the very low polarizability of He. The observed spectra are thus due to induction by overlap forces and similar in origin to spectra observed for rare gas mixtures. The observed spectra are indeed found to resemble those for mixtures of He with rare gases in position and shape as well as in intensity. The spectra are analyzed in terms of a hard sphere potential and an overlap moment varying exponentially with intermolecular separation.