THE INDUCED INFRARED ABSORPTION SPECTRUM OF SOLID DEUTERIUM AND SOLID HYDROGEN DEUTERIDE

Abstract

The fundamental absorption bands of deuterium and hydrogen deuteride have been observed in the solid at a temperature of 1.9 °K. Features are observed that correspond to rotation–vibration transitions in single molecules, in pairs of molecules, and to molecular transitions accompanied by the creation of phonons. Several features were observed in the HD spectrum that arise from the fact that HD is heteronuclear; one of these was a sharp absorption line due to ΔJ = 1 transitions in single molecules. In addition, an unusual split-phonon branch was observed with a minimum of zero absorption a few wave numbers below the frequency of the ΔJ = 1 transition. This split-phonon feature is apparently a result of strong interaction between the rotation of the molecule and its translational motion in the lattice. The spectrum of a solid mixture of 10% HD and 90% H2 was also studied. The phonon branch accompanying the Q1(0) line of HD and the phonon branch accompanying the Q1(0) line of H2 observed in the same crystal have a very different shape, the former exhibiting a distinct minimum as for pure HD.