Goro Kuwabara

Restitution coefficient in a collision between two spheres

On the basis of elastic theory the restitution coefficient e was derived as a function of the elastic constants, radii, masses and colliding velocities of two spheres by taking the visco-elastic property into consideration. For a coefficient close to one, the value of (1-e) was found to be proportional to (velocity)1/5. This result was compared with a treatment based on the plastic property of solids.

E.S.R. Investigation of 3d9 Ions in Alkali-Halides

Cu 2+ in NaCl, LiCl and NaF, and Ni + in NaCl, most of which were produced from Cu + and Ni 2+ by X-ray irradiation were studied by the e.s.r. All of Cu 2+ had elongated tetragonal surroundings, while Ni + had compressed ones. In NaCl: Cu 2+ , the optical dichroism along a cube edge was detected at 5 K corresponding to the Jahn-Teller distortion. From the observed super hyperfine structure of surrounding nuclei the amounts of covalency, f s and f σ were estimated as 0.77 to 0.89% and 7.9 to 12% in the chlorides, respectively. In the case of NaCl: Cu 2+ doped as divalent states, sharp anisotropic spectra without the hyperfine structure due to Cu nucleus were observed, which are presumably due to coagulated ions.

The Optical and Electrical Properties of Cadmium Sulphide Films

The optical and electrical properties of evaporated CdS film were measured. The optical properties are similar to those of the single crystal, that is, the absorption edge lies at 2.4 eV; the photosensitivity peaks near the edge; with temperature decrease, the absorption edge and photosensitivity maximum shift towards shorter wave length; while the electrical properties show wide variation from sample to sample and by heat treatment. The photoresponse shows large dependence on the temperature and is closely related with the dark conductivity. By baking in the air, the conductivity at room temperature decreases by a great deal and the activation energy increases. By baking in the reduced atmosphere, the conductivity, the activation energy and photoresponse almost restore their initial values. In this process, the adsorption or desorption of oxygen on the surfaces of microcrystals plays an important role. The bimolecular recombination argument for the interpretation of spectral sensitivity curves seems inad...

Paramagnetic Resonance of Mn2+ in CsBr

The paramagnetic resonance spectra of Mn 2+ ions in single crystals of CsBr were studied at 9 and 35 GHz. Two different kinds of spectra were observed, which arise from Mn 2+ ions in two different environments; one is a Mn 2+ ion in an aggregated state, and another is a Mn 2+ , which substituted Cs + and is accompanied with a positive ion vacancy in a nearest neighbor cation site. The spin Hamiltonian constants of the spectrum corresponding to the latter were found as g // =1.95±0.02, g ⊥ =2.00±0.02, D =0.390±0.02 cm -1 , A =(90+2)×10 -4 cm -1 .

On the Flare of Lenses

The flare or the stray light in optical systems reduces the image contrast in photography and causes serious errors in photometry. The amount of the flare for small luminous objects was measured by an improved photographic photometry. Generally, the flare originates in two ways, that is, reflections at air-glass interfaces and scatterings by dusts or scratches on glass surfaces. The flare by reflection increases with the area of the illuminated object and attains a saturated value for a large field angle: on the other hand, the flare by scattering slightly depends upon the area. When plotted versus the area or the square of the subtended angle of the target, the amounts of the flare lie on a straight line with several kink points, and the flare by scattering can be determined by extrapolating this line to zero field angle. For a small luminous target, the effect of the flare by reflection is less at a higher relative aperture than at a lower, and the anti-reflection coating greatly reduces the reflected light but slightly enhances the scattered light.

Piezo-optical study of excitons in KI

Abstract The effects of a uniaxial stress along 〈001〉 or 〈110〉 direction on the excitonic structures of KI are studied between 5.5 and 7.5 eV at room temperature by a piezo-modulation technique. Stress dichroism leads to the conclusion that either the second or the third peak corresponds to a transition at the Γ point in the Brillouin zone forming a spin-orbit pair with the first exciton and the other to a transition at the L point. The fourth peak is ascribed to a transition at the L point with an overlaping one at the X point.

Paramagnetic Resonance of Ni2+ Ions in CdCl2

The ESR spectra of Ni 2+ ions in single crystals of CdCl 2 were studied at 9 as well as 35 GHz. A single line was observed at 9 GHz, which was assigned to a forbidden transition between two spin levels M s =±1. The constants in the spin-Hamiltonian were determined as g // =2.25±0.02, g ⊥ =2.22±0.02, | D |=1.35±0.02 cm -1 .

Optical Constants of ZnS Films

The optical constants of the evaporated ZnS film were determined by the photometric and interferometric methods for the wave-length between 400 mµ and 1000 mµ. The results obtained by both methods agree within the experimental error, and the density of the film calculated by Lorenz-Lorenz formula is ca. 0.98 of that of the bulk ZnS .

Phonon Structures in Reflection Spectrum of Red Mercury Iodide

Optical spectrum of red HgI 2 in the A exciton region was studied by means of wavelength modulated reflectance and magnetic circular dichroism. Many fine structures are observed, some of which shift diamagnetically parallel to each other with an LO phonon energy interval. They are assigned as phonon replicas of the 2 s exciton.

Raman spectra of K2CuF4

Abstract The crystal structure of K 2 CuF 4 has been studied by means of Raman scattering. The structure is found to belong to the space group D 4 h 5 rather than D 4 h 17 of K 2 NiF 4 between 2 and 800 K because of the distortion arising from the “orbital ordering effect”.