Formation mechanism of color centers in alkali halide crystals have been reviewed through experimental results by pulsed electron beam (30 MeV, 0.8 A, 10 ns or 0.5 MeV, 7000 A, 3 ns). Negative ion vacancies had been considered to be main products due to radiation effects in alkali halide crystals. According to the results by pulsed electron beam, however, it is rather plausible to suggest that Frenkel pair consisting of a negagtive ion vacancy with an electron (F center) and an interstitial halogen atom (H center) is the primary main product due to the radiation. Excitons play important role for the production of such an Frenkel pair. The characteristics of color centers, absorption and emission bands due to color centers and defects being related to the color center production in all crystals investigated up to date are summarized in Tables.
Positron annihilation including the author and his collaborators' experiments is reviewed. The studies of lattice defects by means of positron annihilation which are recently rapidly developing are emphasized.
Quenched compounds (Bi1-xSbx)2 (Te1-ySey)3 were given heat treatment for 10hr. at 400C., and Hall coefficient R and electrical conductivity σ were measured over a temperature range of 80-300K. It was found that composition of compounds with vanishing Hall coefficient is approximately given by x=(y-0.25)2+0.35 at 100K. Hall coefficient hardly changes with temperature but does change with composition. Composition dependence of electrical conductivity is approximately expressed by σ∝[ax(1-x)+by(1-y)+c]-1, where a, b and c are constants Temperature dependence of electrical conductivity is more gradual than T-1.5. The following conclusions are obtained from a discussion of the experimental results; (1) Impurity and alloy scattering are as important factors of scattering mechanism as acoustical lattice scattering in many compounds. (2) Carriers of these compounds are almost invariably the lattice defects themselves. (3) Composition dependence of electrical conductivity is given by the factor (m*5/2ED2), where m* is the effective mass of a charged carrier and ED is the deformation potential. (4) Conduction and valence bands both consist of two bands.
A method is proposed for analysing the fluorescence pulse by means of a graphical calculation to deduce its lifetime, when the decay of the exciting light pulse is approximately exponential. Using this method, the lifetime of a glass filter (Toshiba V-Y43) has been measured to be 0.25±0.03μsec.
The refractive indices nx, ny, nz of nonlinear optical crystal HIO3 were determined in the wavelength range between 0.35 and 1.6μm by use of two prisms made of the crystal. The crystal was grown by means of a water solution method. We also evaluated the constants in the single-term Sellmeier dispersion relation from the measured indices. It is found that this relation is valid in the wavelength region from approximately 0.4μm to 1.2μm.