Spin lattice relaxation time T₁ in KOH-doped ice was measured with the pulse NMR method between the temperature range from just below melting point to 100K(-173°C).The excitation magnetic frequencies were 13.1, 24.1, 31.4 and 47.5 MHz. Temperature and frequency dependence of T₁ was successfully analyzed using two spin systems which have different proton motion states. Comparison of the temperature dependence of the coupling constant between two spin systems and that of the dielectric relaxation showed that the rapid dielectric relaxation excited by KOH doping corresponds to the transfer motion of protons on the hydrogen bond and is stabilized below about 200K.

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A load of the cantilever type was applied to a test piece cut from a single crystal of ice. When the test piece bent, the load applied to the test piece was reversed. This cycle was repeated. Work hardening did not occur though this cycle was repeated many times. This is explained as follows. Dislocation with the Burger's vector of the a-axis was responsible for the deformation of the test piece. Dislocation with the Burger's vector of the c-axis did not occur. Therefore, the dislocations are not tangled, and work hardening does not occur.

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We demonstrated photon emission during deformation and fracture of axially loaded polycrystalline ice. Emission of visible photons(300-650nm)was confirmed in accordance with crack generation and fracture. Time-resolved photon emission signals are presented along with load changes. After the intense emission occurring at a fracture event, there were several weak emissions which lasted for a few seconds. Emission intensity, including entire spectra ranging from 300 to 650nm, roughly increased with increasing strain energy released by fracture, while scattering in the intensity data showed that emission intensity also strongly depended on the characteristics of each individual crack. Intense emission contained shorter wavelengths than 320nm, indicating that near ultraviolet light is possibly emitted. Emission intensity and spectra may be attributed to microprocesses during fracture. Experimental evidence indicates that the generated electric charge on crack surfaces and at crack tips should have higher energy than that of the electrical potential difference reported previously (Fifolt et al.1993).

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The morphology of an ice crystal changes from a thin disk, to a perturbed disk and finally to a dendrite with hexagonal symmetry. Since the thickness is very small, ice crystals have been analyzed in two dimensions. Therefore, we carried out in-situ observations of ice crystals growing in supercooled pure water using a new experimental apparatus combined with a MachZehender interferometer. Three-dimensional patterns of ice crystals were analyzed by the interference fringes obtained. The crystal growth process was found to occur in two stages, namely, disk growth and dendritic growth stages. In the first stage, we found that the trajectories of disk growth were categorized in two types, depending on the growth mechanism of basal interfaces. Furthermore we found that the critical factor of morphological instability on the ice disk is not its radius, but its thickness. We also found that the three dimensional pattern of ice is very asymmetric in the direction of the c-axis. In the second stage, the supercooling temperature dependence of growth rates at the dendrite tips is consistent with the universal law of dendritic growth, in which the effects of thermal diffusion and interfacial tension are taken into account, but that of the tip radii is not. These results mean that the effect of interfacial kinetics is intrinsically important to understand the pattern formation mechanism of ice.

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[in Japanese]

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The mechanism of temperature dependence of ice crystal habit growing from the vapor phase at low supersaturation was experimentally studied.The habit change of ice crystals with temperature can be explained by the temperature dependence of the anisotropy of the slope of growth hillocks formed on the {0001} and {1010} faces of the ice crystals.
In addition, the fomation mechanism of the side branches (secondary branches) of dendritic ice crystals growing at high supersaturation was experimentally studied. The fomation mechanism of side branches of dendritic ice crystals growing at the supersaturation near water saturation was found to be different from that above water saturation.

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