レーザー光による多結晶氷の光学的構造の解析

概要

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Several specimens of polycrystalline ice were optically analysed using a polarization apparatus equipped with a gas laser light source (6, 328 Å in wave length, 1mmφ in beam width). Placing a disk-type ice crystal at a right angle to the light beam axis, the optically characteristic parameters of polarization analysis, the retardation phase difference between ordinary and extraordinary lights and the angle of inclination of polarization ellipsoid in the specimen were measured. To form the ice crystal disk, distilled and boiled water drops (ca. 0.5 cm in diameter) were frozen in the temperature range of -8 to -13°C on a glass substrate and were cut into thin disks (0.016cm in thickness) adhering at the glass. The laser light beam was projected and the optical parameters were measured in a 1 mm square mesh pattern which was regarded as a single crystal grain for convenience. Quartz and mica disks were used for reference. The analysis revealed that the correlation coefficients for the orientation of main axis between adjacent crystal grains were quite small and in spite of this the mean orientation was estimated to be rather parallel to the light beam axis (i. e., perpendicular to the ice disk plane). The effect of NaCl contamination in the optical parameters was not noticed so far as the observation of six specimens is concerned.