The induced spectra of compressed helium–argon and neon–argon mixtures, and of compressed hydrogen, nitrogen, and oxygen have been measured in the frequency region 20 to 400 cm−1. The far-infrared spectra consist of a translational branch and a rotational branch which overlap, except in the rare-gas mixtures where only the translational component exists. The latter is a broad band which extends from zero frequency to about 500 cm−1, with a maximum near 150 cm−1 in the room-temperature gas. In the case of hydrogen the translational branch is readily distinguished from the rotational branch because it lies at a lower frequency than the latter. In the case of oxygen and nitrogen the spacing between the rotational lines is small and the translational and rotational branches overlap completely.
