Far-Infrared Spectra of the Ices

Abstract

Over the past few years the ir spectra of six of the nine known phases of ice have been studied between 4000 and about 50 cm−1. These spectra show the influence of six different intermolecular environments upon the spectra of the same molecule. In this paper the far-ir spectra of ices 1h and 1c will be reviewed and compared with those of ices II, V, VI, and IX, which are discussed in detail for the first time. The far-ir absorptions arise from the translational lattice vibrations of the solid. The spectra of the orientationally disordered phases, 1h, 1c, V, and VI differ strikingly from those of the ordered phases, II and IX. The ordered phases have spectra that are qualitatively similar to the spectra of nonhydrogenbonded ordered molecular crystals, and agree approximately with the predictions of the Factor Group analyses. The disordered phases all shown extremely broad absorptions owing to the relaxation of the zero-wavevector selection rule.