Absorption Spectra of Hydrogen-Halide—Rare Gas Mixtures

Abstract

The null‐gap regions of the 1–0 bands of HCl and HBr have been investigated with a grating spectrograph of very high resolution. The experiments were performed using an absorption tube of 90 cm length and a hydrogen‐halide pressure of 25 cm Hg. The hydrogen halide was pressurized with argon, krypton, or xenon of density 2 to 5 amagats. The sensitivity of the apparatus was such that absorption features 10^—4 the intensity of the P(1) line of HCl could be observed with ease. The absorption features observed are complex, relatively sharp, and totally different when argon, krypton, or xenon is used as the pressurizing gas. It is suggested that the hydrogen‐halide molecule forms a molecular complex with the rare‐gas atoms used as pressurizing agents. The discrete induced absorption features have an intensity considerably less than 10^—3 of the intensity of the P(1) line of HCl per amagat density of pressurizing gas. In HBr the ``induced absorption features'' have approximately two to three times the relative intensity observed in HCl.