Studies in Molecular Dynamics by Collision-Induced Infrared Absorption in H2–Rare Gas Mixtures. I. Profile Analysis and the Intercollisional Interference Effect

Abstract

The pressure-induced infrared fundamental band of hydrogen in H2–rare gas mixtures was recorded over a wide range of temperatures (77–300 K) and densities (5–1200 amagat) using pressures up to 2000 atm. By assuming appropriate line shapes for overlap- and quadrupole-induced transitions the band profiles could be computer analyzed in terms of essentially three parameters, δd, δc, and δq. The value of δd, the half-width of overlap-induced transitions, was found to be density independent, thus indicating the very short range of this induction process. The half-width, δc, of the intercollisional interference dip for overlap-induced transitions increases with the density, ρ, according to the equation, [Formula: see text]. The collision cross section for overlap induction, calculated from the linear coefficient a, is ~10% greater than the Lennard–Jones σ12. The relation of δc to the diffusion coefficient D12 of H2 molecules in the rare gas is discussed. Data on the half-width δq of quadrupole-induced transitions will be analyzed in paper II of this series.