Recent developments in the research on the structure of chiral nematic liquid crystals are reviewed. The cholesteric liquid crystalline phase of mixtures comprised of nematic or chiral nematic liquid crystal and cholesteric liquid crystal is discussed by means of the extended Goossens theory. Change of pitch in the spiral structure of the mixtures with temperature is also discussed.
The fractions of desorption of monomolecular multilayer films consisted of cobalt-hydrogen stearate in vacuum at about 24°C and under X-ray irradiation in vacuum are measured using radioisotope tracer technique and photoelectron intensity change in an ESCA instrument. The film labeled with 14C or 60Co is deposited on gold substratum by Blodgett method. In vacuum, only a part of the stearic acid molecules in the multilayer film are lost. The fraction of desorption, ƒ, of n layer film is expressed by ƒ_??_(1-α)n. Here, α is nearly equal to the conversion ratio of stearic acid molecules to cobalt stearate. Under the X-ray irradiation in vacuum, there are “fast” desorption which is due to the desorption of stearic acid molecules and “slow” desorption mainly caused by the rupture of mol-ecules. The structure of the film after the “fast” desorption is considered to be sub-skelton.
A compact X-ray generator with high speed rotating anode (1_??_1.5×104rpm) has been constructed. The merits and limits of the high speed rotation were estimated. The rotor is. 9cm diam. and oil-cooled. The slender rotating axis supported at both ends is driven directly by a water-cooled high frequency motor. The vacuum seals are loose oil-seals helped by the centrifugal action of a flat ring attached to the axis. A special brush was used to remove any contamination of the rotor.
Thin film GaAlAs/GaAs solar cells have been fabricated by the Peeled Film Technology (PFT). The GaAlAs/GaAs solar cell structure (_??_20μm) and undoped Ga0.3Al0.7As layer (_??_5μm) are grown on the GaAs (111) substrate. The Gaos oAlo.7As layer is etched selectively by HF to obtain a thin film GaAlAs/GaAs layer. Electron mobility and diffusion length for minority carriers are measured to characterize the thin film GaAs layer. The typical energy conversion efficiency of Zn diffused GaAs solar cells fabricated by the PFT is found to be 11%, and the preliminary nGaAlAs/pGaAs solar cells showed on efficiency of up to 13% in sun light. Thus, highly efficient thin film solar cells can be formed by the PFT.
Luminescent characteristics for high-power dye lasers, whose risetime is short (_??_1μs) compared with the conventional xenon flashlamp, are investigated experimentally. Both linear and coaxial flashlamps with various sizes are examined under the same condition. The lumi-nescent efficiencies of linear flashlamps do not almost depend on the variety of gas and its pressure, because of the wall ablation. The optimum size is decided for a linear lamp. On the contrary, a remarkable dependence on gas pressure is observed in case of coaxial lamps, and the relation to the critical damping is studied. A result on the running test of various linear flashlamps is given and discussed.
The composition dependence of the helical pitch, λ0=np, was measured in ten mixtures of nematic compounds and cholesteryl propionate. The plot of 1/λ0 against composition is found to deviate considerably from a straight line in some of these mixtures. The deviation is discussed in relation to the molecular structure of nematic components, and it is shown that the lateral intermolecular interaction is of importance in determining the helical pitch of mixtures.