Yoshiki Sato

Potential Barrier for Hindered Rotation in Molecular Crystal

A method is described for determining the height of the potential barrier for hindered rotation in a molecular crystal, in which the intensity of infrared absorption band is measured for different angles of polarization as a function of temperature. The barrier height is obtained from an average value of temperatures at which the “intensity versus temperature” curves intersect. Further, an empirical relationship is given between the potential barriers and frequencies of hindered rotation in various compounds, which is well approximated by begin{aligned} V{=}0.64-0.016{cdot}10^{-2}nu+0.31{cdot}10^{-4}nu^{2}{pm}0.27, end{aligned} where V denotes the former in Kcal/mole and ν the latter in cm -1 .

Optical Study of Electronic Structure of Graphite

Reflectance spectra of pyrolytic graphite are measured in the range 0.13 to 0.006 eV. The results are analyzed by a Kramers-Kronig relation to determine the complex dielectric constant e(ω)=e 1 + i e 2 and energy loss function. Structures in e 2 are all identified with interband transitions between the doubly degenerate levels at the points K and H of the Brillouin zone split by the effect of spin-orbit interaction. From the above fact, the strength of the coupling λ and the band parameter Δ are estimated as 0.004 eV (at the point K ) or 0.0023 eV (at the point H ) and -0.016 eV, respectively. Two peaks observed in -Im e -1 are interpreted as plasma frequencies of free electrons at the Fermi surface perpendicular and parallel to the crystallographic c axis.

Infrared Investigation of the Phase Transition in NaNO3

Absorption spectra of a combination mode ν 1 +ν 4 of NaNO 3 single crystal are studied over the temperature range between 26°C and 29°C with a polarized infrared radiation. It is found that as temperature rises halfband width markedly broadens as the temperature approaches the transition point of 275°C. The band shape in the high temperature phase is in good agreement with the relative intensity distribution curve calculated on an assumption that the NO 3 ions are rotating freely around the threefold axis. The broadening of the band at any temperature can be explained satisfactorily if the two contours of the band observed at 26°C and 275°C, respectively, are superposed with an appropriate intensity ratio.

Catalytic effect of metallic halide on non-solvent coal hydrogenation at short contact time

Abstract Both catalytic and non-catalytic hydrogenations of Japanese coal have been studied using an autoclave equipped with a magnedrive device at temperatures 500–600 °C and hydrogen pressure 4.9–14.7 MPa (gauge) in the absence of solvent. Gas yield decreased but extraction yield with pyridine increased markedly in the reaction using ZnCl 2 or SnCl 2 · 2H 2 O as a catalyst in comparison with the non-catalytic reaction. The structural parameters of extracts derived in both reactions were determined, and showed only slight differences.

Deep magnetic polaron state in Gd2S3

Abstract Reflectivity spectra of a magnetic semiconductor Gd 2 S 3 were measured and the photon energy range from 0.05 to 0.5 eV at 14 K under magnetic field up to 5T. The energy position of the peak at about 0.1 eV shifts to the lower energies and the peak width becomes broad as the magnetic field increases. This behavior is thought to evidence that this structure is due to the optical absorption of deep levels of the magnetic polaron of Gd 2 S 3 .

Far infrared reflectivity spectrum of Gd3−xVxS4(x = 13) under a magnetic field

Abstract The reflectivity spectrum of Gd3−xVxS4 (V denotes a vacancy and x = 1 3 ) has been measured in the photon energy range from 2 to 40 meV at 9 K under magnetic fields up to 5 T. The energy gap of about 7 meV was observed to become narrow with an increase of the magnetic field and disappears above 3 T. This shows the collapse of the magnetic polaron state.

Nonsolvent coal hydrogenation at short contact time

Abstract Yields and properties of products on hydrogenation of Japanese and Australian coals have been studied using an autoclave equipped with a magnedrive device at temperatures of 500–600 °C and hydrogen pressure 4.9–14.7 MPa (gauge) in the absence of solvent. Optimum contact time, at which maximum extraction yield was observed, shifted from 15 s to a few seconds with increasing reaction temperature and hydrogen pressure. The extracts derived from both coals reveal similar structural parameters.

Liquefaction of blended coal

Abstract The effect on liquefaction of the blending of two coals of different rank has been evaluated in a conventional autoclave experiment at ≈400 °C by the solvent-refined coal (SRC) method as well as by short-contact-time hydrogenation at temperatures up to 550 °C without solvent and using a specially designed cylindrical autoclave. Using the latter method, higher conversions of coal to gas and liquid, than those calculated by the additivity rule, were observed.

Catalytic hydropyrolysis of western Canadian coal combined with critical gas extraction

ABSTRACT Experimental results of catalytic hydropyrolysis combined with solvent extraction near critical conditions of an Alberta subbituminus coal indicated a conversion of 40 wt% of coal to hydrocarbon products. The effects of catalyst and solvent on the structural parameters of the extracts were evaluated from the modified Brown-Ladners equation. Both alcoholic and aromatic solvents and Lewis acids (ZnCl2 and SnCl2 2HO2) showed Increased yields of hydrocarbon products, but the presence of hydrogen was necessary to improve this yield.

Splitting Fermi Surfaces and Heavy Electronic States in Non-Centrosymmetric U3Ni3Sn4

We report the single-crystal growth of the non-centrosymmetric paramagnet U3Ni3Sn4 by the Bridgman method and the Fermi surface properties detected by de Haas–van Alphen (dHvA) experiments. We have also investigated single-crystal U3Ni3Sn4 by single-crystal X-ray diffraction, magnetization, electrical resistivity, and heat capacity measurements. The angular dependence of the dHvA frequencies reveals many closed Fermi surfaces, which are nearly spherical in topology. The experimental results are in good agreement with local density approximation (LDA) band structure calculations based on the 5f-itinerant model. The band structure calculation predicts many Fermi surfaces, mostly with spherical shape, derived from 12 bands crossing the Fermi energy. To our knowledge, the splitting of Fermi surfaces due to the non-centrosymmetric crystal in 5f-electron systems is experimentally detected for the first time. The temperature dependence of the dHvA amplitude reveals a large cyclotron effective mass of up to 35 m0...