The Raman spectra of H2O and D2O ice VIII recovered at ∼100 K and zero pressure have been measured in the range 4000–50 cm−1. The three stretching, three rotational, and four translational bands expected from the symmetry of the crystal have been identified. Two bending bands are expected and have been tentatively identified among some weak bands. The relative intensity of the rotational and stretching bands is much smaller than in the vapor, and so if the intensity of the stretching bands is not greatly changed, the anisotropy of the polarizability is appreciably smaller in ice VIII than in the vapor.

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Articles you may be interested inEffect of pressure on the Raman spectrum of translational lattice vibrations in ice J. Chem. Phys. 69, 5557 (1978); 10.1063/1.436551 Optical spectra of orientationally disordered crystal. V. Raman spectrum of ice Ih in the range 4000-350 cm−1The Raman spectrum of the translational vibrations of polycrystalline ice Ih has been investigated in the range 350-20 cm -I. All the vibrations are Raman active, and there is much fine structure, presumably due to particular points in the Brillouin zone. Tentative assignments are suggested for some of the features. The theory of the Raman scattering by the translational vibrations of orientationally disordered crystals has been discussed and it is shown that the origin of the Raman intensity lies mainly in the disorder in the location of the hydrogen atoms surrounding an O-H···O bond. The intensity of scattering below ~2OO cm-I is much weaker than that above ~240 cm-I , which suggests that while the vibrations below ~2OO cm-I are disorder allowed, those above ~240 cm-I might be connected with the order-allowed A Ig , E Ig , and E2 g vibrations of the hypothetical crystal with real hexagonal symmetry. The strong Raman scattering near 310 cm -I is not caused by a splitting of the transverse and longitudinal optic vibrations, such as occurs in ionic crystals, but by significant electrostatic interactions, particularly of the transition moments of neighboring hydrogen bonds. They cause the hydrogen-bond stretching constant to depend on the relative orientation of the two water molecules, and the coupling constant for the stretching of neighboring hydrogen bonds to differ for the symmetric, O-H···O···H-O and O···H-O-H .. ·O, and asymmetric, O-H .. ·O-H .. ·O, configurations. The differing coupling constants cause significant differences in the forces restricting the motion of molecules parallel and perpendicular to their polar axes, and probably causes the peaks in the spectrum at ~31O and 228 cm-I .Many of the strong features observed have been re-

The temperature dependences of the Raman spectra of aqueous dispersions of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were monitored at different but constant pressures between 1 and 1210 bar. The changes observed in these Raman spectra are discussed in terms of the effects of high pressure on the phase state and molecular structure of lipid bilayers. It is demonstrated that the temperature of the endothermic gel to liquid-crystal phase transition, as well as the temperature of the pretransition, increases linearly with increasing hydrostatic pressure. The dTm/dP values obtained from a wide range of pressures are 20.8 degrees C X kbar-1 for DPPC and 20.1 degrees C X kbar-1 for DMPC. The dTp/dP value for DPPC is 16.2 degrees C X kbar-1. It is also shown that the volume change that occurs at the gel to liquid-crystal transition is not constant; i.e., d delta Vm/dP decreases by 6.2% (DPPC) or 6.3% (DMPC) per kilobar pressure. The volume change at the pretransition is also pressure dependent; the d delta Vp/dP value of DPPC decreases by 4.7% per kilobar pressure.