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The amplitude of the orientational dielectric dispersion of impure polycrystalline ice Ih has been measured at temperatures down to 133 K in an attempt to find evidence for an ordering transition. The Curie–Weiss temperature is 6.2±1.7 K and so, within the experimental precision, there is no significant evidence that the molecular orientations become more correlated than the ice rules require. From the most recent results on polycrystalline ice, the Curie–Weiss temperature is 15±∼11 K. As this temperature is far below the lowest experimental temperatures, the evidence for an ordering temperature is not firm. The activation energy for dielectric relaxation in the impure ice is 25.5 kJ mol−1 at high temperature and increases at low temperatures. The low activation energy is caused by impurities that generate orientational defects in about the maximum number physically possible, and is mainly the activation energy for diffusion of the defects. At lower temperatures, the impurities produce fewer defects and the activation energy rises because the energy required to produce the defects begins to contribute to it. The low-temperature region in D2O ice with unknown dopants, which has been well studied by Johari and Jones and by Kawada, is due to this effect. An analysis suggests that the low-temperature region would be well worth studying for a sample with known dopants.

Articles you may be interested inThe infrared spectrum of ice IV in the range 4000-400 cm−1 J. Chem. Phys. 71, 4050 (1979); 10.1063/1.438173Optical spectra of orientationally disordered crystal. V. Raman spectrum of ice Ih in the range 4000-350 cm−1 P 0 SIT RON I U M C HEM 1ST R YIN A QUE 0 U S K M n 0 4 SOL UTI 0 N S 4501 identification card and a control card. The control card contains the value of the intercept (A) at point P, the decay constant >' 2, the background counts, and the number X whose value is relative to the point P=O. The program now reads data points from point B to (X-1) and performs background subtraction. THE JOURNAL OF CHEMICAL PHYSICSThe data points from the least-squares curve XD are now read in and compared point by point with curve PD until the point D is determined. The program now proceeds to find Area 1, Area 2, Area 3, and the intensity 12• The results are printed out and the program proceeds to the next data set.The absorbance of several samples of ice Ih has been measured in the range 4000-30 em-I, and scaled to that of a particular film of unknown thickness. The thickness of the film has been calculated by two methods, first from the known absorptivity at 4940 em-I, and second by equating the appropriate Kramers-Kronig integral to the known infrared contribution to the microwave refractive index. The two thicknesses agreed well and allowed the absorptivity to be obtained in the range 4000-30 em-I. The complex refractive index and permittivity and the normal incidence reflectivity have been calculated from the absorptivity. About three-quarters of the infrared contribution to the microwave refractive index is caused by the translational lattice vibrations and about 15% by the rotational vibrations; the o-H stretching bands which absorb very strongly contribute relatively little. The maximum of the density of states in the transverse acoustic branch is at 65 em-I rather than below 50 em-I as reported earlier. Below 50 cm-I the absorptivity is roughly proportional to the fourth power of the frequency. This arises because the vibrations here are short-wavelength sound waves with a density approximately proportional to the square of the frequency, and the integrated intensity of absorption by one vibration is proportional to the square of the frequency. A theory of the contribution of the translational lattice vibrations to the microwave permittivity is given based on the theory of the absorption by orientationally disordered crystals given in an earlier paper. From the theory and the experimental measurements reported in this paper the dipole-moment derivative for the relative displacement of two water molecules in ice along their line of centers (or equivalently the effective charge of a water molecule) is about 0.3 electronic charges.

The infrared spectra of CH3OH, CH3OD, CD3OH, and CD3OD in the five phases gas, liquid, vitreous solid, α-crystal, and (except perhaps for CD3OH and CD3OD for which the solid-solid transitions have not been studied) β-crystal have been recorded in the range 4000 to 300 cm−1. The Raman spectrum of liquid CD3OH has been recorded. A complete assignment of the internal modes is given, which differs somewhat from previous assignments for the CH3 bending and rocking vibrations. No significant difference in spectrum occurred between the α-crystal and β-crystal phases. Under the full symmetry of the β-phase determined by x-ray diffraction only one OH out-of-plane bending band should occur. Two bands are observed, and it is concluded that the carbon and oxygen atoms in one chain are not coplanar, as is required by the symmetry determined by x-ray diffraction [K. J. Tauer and W. N. Lipscomb, Acta Cryst. 5, 606 (1952)], but that the chains are puckered and the x-ray symmetry arises because the puckered chains are irregularly distributed, a structure that had been previously suggested by Tauer and Lipscomb tentatively on the basis of high apparent thermal amplitudes. Bands occur in the crystal spectra near 500 cm−1 and 340 cm−1 at −180°C. These are interpreted as lattice modes, probably the two infrared-active modes that involve translations of the molecules.