Infrared absorption spectra of gaseous HD. III. Collision-induced fundamental band of HD in HD–Kr and HD–Xe mixtures at room temperature

Abstract

Spectra of the enhancement of absorption of the collision-induced infrared fundamental band of HD in HD–Kr and HD–Xe mixtures have been investigated at room temperature for different base densities of HD and a number of total gas densities up to 140 amagat. These spectra exhibit a narrow line at the R1(1) position, in addition to the well known collision-induced O, Q, and S branches. The occurrence of this new feature in the enhancement spectra, as explained recently by us elsewhere, is due to a phenomenon termed ’’intracollisional interference.’’ The binary absorption coefficients of the band derived from the measured integrated absorption coefficients are (6.3±0.1) ×10−35 and (10.1±0.3) ×10−35 cm6 s−1 for HD–Kr and HD–Xe, respectively. The characteristic half-width parameters, δd and δc of the overlap-induced transitions, and δq (and δq′) of the quadrupole-induced transitions are derived for both HD–Kr and HD–Xe from an analysis of the profiles of the enhancement of absorption. As described in Papers I and II of this series for other binary mixtures of HD, the variation of δc, the half-width of the intercollisional dip of the Q branch, with the density of the perturbing gas Kr as well as Xe has been investigated. In both HD–Kr and HD–Xe, the quadrupole-induced transitions show negative wavenumber shifts from the corresponding calculated positions for the free HD molecule. In particular, for HD–Xe, these (∼7 cm−1 at a density of 70 amagat of Xe) are found to vary linearly with the partial density of Xe.