Studies in Molecular Dynamics by Collision Induced Infrared Absorption in H2–Rare Gas Mixtures. III. H2–He Mixtures at Low Temperatures and Densities

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Abstract
The collision induced fundamental band of H2 has been studied in H2–He mixtures with absorption paths of 110 and 165 m in a low temperature multiple traversal cell. Spectra were obtained at 18 and 61.5 K with densities in the range of 9 to 60 amagat. Under these conditions the structure of the band is particularly simple and amenable to analysis; the results of a profile analysis of the present spectra are compared with the higher temperature and density results in paper I (Mactaggart and Welsh) of this series. The long observed splitting of the Q branch of the H2 fundamental is manifested here as very sharp dips in the absorption profile at the Q1(0) and Q1(1) molecular frequencies and these provide a striking confirmation of Van Kranendonk's explanation of the 'splitting' as due to an intercollisional interference effect.