Interference effects in the spectrum of HD: II. The fundamental band for HD–rare gas mixtures

Abstract

The absorption spectrum of the fundamental band of HD (λ ≈ 2.7 μm) has been studied at high resolution in mixtures with the rare gases He, Ne, and Ar at low temperatures (77 and 145 K) and moderate densities (<205 amagat). Interference effects that occur between the collision-induced transitions and the dipole-allowed transitions of free HD were analyzed as a function of density and collision-partner. The R(0) and R(1)dipole transitions exhibited large changes in shape and intensity at high densities, but their behaviours were quite different from each other. Like the pure HD samples, the line shapes were well represented by series of Fano profiles, and the density dependences of the lines were well explained by the theory of Herman, Tipping, and Poll. These results should greatly improve the understanding of the physical processes underlying the interference effects.