A review is made on studies of high-frequency sound near the ferroelectric transition temperature. Observed quantities are the sound velocity and the attenuation coefficient in ultrasonic measurements, and the Brillouin shift and the line width in Brillouin scattering experiments. Anomalies of these quantities are recently interested in as static and dynamical critical phenomena. Since precise reliable data of temperature dependence are indispensable for this purpose, recent developments of experimental techniques are shortly reviewed. A unified phenomenological treatment is tried to demonstrate the relation of these quantities with complex diectric constant, the specific heat and the energy relaxation time which become anomalous near the transition temperature. Typical experimental results are shown in parallel to this discussion, respectively. Studies of the energy relaxation time, the depolarization effect and the central mode are discussed as characteristic applications of present methods.
Present status of mode-locked pico-second pulse lasers and their applications to quantum physics of matters is extensively reviewed. It is pointed out that the features of pico-second light pulses exist in their ultra high peak powers and ultra short durations. Emphasis is placed on the nonlinear and transient responces of matters caused by such features. First, recent progresses on nonlinear optical phenomena, ultra fast relaxation phenomena and dynamical behaviour of highly excited materials, made by means of pico-second spectroscopy, are extensively reviewed. Second, coherent mixed states of light and matter and nonlinear resonant phenomena in the pico-second regions are suggested as future problems. Finally pico-second lasers to be developed, including X-ray lasers, and their applications to nuclear fusions are briefly mentioned.
A comparative quartz dilatometer is described which uses a differential transformer and a lock-in amplifier. The instrument can be operated at temperature from -196°C (liq. N2) to ca. 350°C with a sensitivity of Δl_??_5×10-5mm. Thermal expansion measurements are presented for Ni metal and some antiferroelectric ceramics such as PbZrO3, Pb(MgW)1/2O3, and Pb(Fe2/3U1/3)O3.
When a KCl single crystal is grown by rapid cooling of the melt, the crystal cleaves naturally into fragments. In the natural or artifical cleavage of the crystal various step lines appear on the cleaved surfaces. In the present paper we observed that the shape of a line is straight along the 100-axis and a wavy confusion or zigzag along the 110-axis. Such a confusion of the shape may be described by introducing two confusion factors: G a visual one (G=0 for a straight line) and b defined from the orientation (b=0 along the 100-axis). On the other hand, a sinusoidal approximation of the line gives the wavelength λ. Then we have G_??_b and λ is a function of b. The confusion of the shape of the lines is also related to the macroscopic defects.
A new method for determining the dew point by injecting water into a sample gas of constant volume is investigated. A sample gas and a dry gas are contained in two vessels of equal volume which are connected to a U-tube manometer between them. Firstly, both the gases are at the same temperature T1 K and equal pressure. Secondly, the temperature of both the gases are changed to a suitable temperature T2(T2_??_T1) K, and then a difinite amount of water is injected into the sample gas. The dew point, if the volumes of the gases are kept unchanged, is determined theoretically from the three measured quantities, namely, T1 K, T2 K and the pressure difference between the gases. When the volume of the gases are not kept strictly constant, the correction due to volume change by the injecting water and the pressure of the manometer is discussed. Experimental data measured with the air passed through the saturator are presented. The experimental results show that the dew point can be accurately determined by the above mentioned method.
Temperature-gradient liquid-phase-epitaxial growth technique for Gal-xA1xAs thick layers with almost uniform composition is reported. In this technique, using a relatively small amount of the Ga solution, the Gal-xA1xAs source was prepared by adding excess amounts of GaAs and Al source materials to the Ga solution and by using a temperature-overshoot method. GaAs substrates were made contact with the solutions by a slide method for obtaining identical layers with high reproducibility. It has been clarified that the composition of the grown layers depends on the amounts of the excess materials, overshoot temperature and growth temperature. Under the optimun condition, 300 to 500μm thick Gal-xA1xAs layers with almost uniform composition were grown. Under certain other conditions, layers whose AlAs composition increased along the growth direction were obtained. These thick layers have been used for dome-shaped Gal-xA1xAs LEDs, which have a maximum of 53 mW output and 18.3% external quantum efficiency.
Liquid scintillation methods with coincidence techniques have been applied to the low-level radon measurement in order to reduce background. The methods are based on the principle of either coincidence or pile-up effect between β- rays from RaC and α rays from RaC' with a very short half-life of 162μsec. Pair pulses of RaC-C', which correlate with the time duration selected by the pulse shaping, can be discriminated from other single pulses, including background. The counting efficiency calculated from the time duration agreed well with the experimental results, and adsorption of radon daughters in the walls of the counting vial was observed. The background of the methods caused by the statistical random coincidence or pile-up depends on the total counting rate of the sample and the time duration. A background counting rate of less than 0.01 cpm is attained without any serious decrease in counting efficiency.