Raman spectra of the O–H and O–D stretching vibrations of ices II and IX to 25 °K at atmospheric pressure

The Raman scattering by the stretching modes of H2O and D2O in the ordered phases ice II and ice IX is reported for temperatures between 100 and 25 °K. The observed features are assigned to k=0 modes with the aid of polarization data from oriented crystals of D2O ice II and the normal coordinate calculations which have previously explained the infrared spectra [J. E. Bertie and F. E. Bates, J. Chem. Phys. 67, 1511 (1977)]. It is shown that normal coordinate, bond moment, and bond polarizability, calculations satisfactorily explain the frequencies and relative intensities in both the infrared and Raman bands due to the D2O stretching modes in these phases. These Raman bands are nearly insensitive to the order or disorder of the water molecules in phases of ice. The O–D stretching modes of ice IX that have large infrared intensities have weak Raman intensities, and no longitudinal optic modes can be clearly identified in the Raman spectra. The frequencies of the LO modes have been estimated for ices II and IX. The magnitudes of the LO–TO splittings suggest that the infrared transmission spectra may be broadened by reflection effects resulting from the dispersion of the refractive index, and the sharpness of the Raman bands suggests that the breadth of the infrared bands is not primarily due to Fermi resonance with high-order overtone and combination levels, as was previously proposed.