Far-infrared absorption by ices Ih and Ic at 4.3 °K and the powder diffraction pattern of ice Ic

Abstract

The far‐infrared spectra of H₂O and D₂O ices Ih and Ic at 4.3 °K are reported. Many weak features are observed and for ice Ih are shown to correspond well with features in the published Raman spectra. Differences between the spectra of ices Ih and Ic are reported for the first time; they are due to the different crystal structures and can be understood in more detail from published calculations of dispersion curves and densities of translational vibrational states. These results and the Raman spectra provide much information with which to test calculations of the translational vibrations in ice I. Extra lines in powder diffraction patterns of ice Ic have generally been attributed to ice Ih impurity. From the measurements reported in this work it is suggested that this may not be the case.