Xenon-plasma light ultrahigh-resolution ARPES study of low-energy single-particle excitation gap in (Bi,Pb)2Sr2CuO6

We have performed ultrahigh-resolution angle-resolved photoemission spectroscopy of (Bi,Pb)₂Sr₂CuO₆ by using a newly developed xenon-plasma light source to clarify the origin of the pseudogap (PG). We determined the comprehensive momentum and temperature dependences of the superconducting (SC) gap and the PG, and revealed a smooth evolution of the PG from the SC gap. We also found a linear scaling behavior of the characteristic PG temperature with the SC gap size regardless of the momentum location. These experimental results strongly suggest that the observed PG is caused by the precursor pairing.     

Temperature dependence of the electronic structure of Sr14Cu24O41 studied by resonant inelastic X-ray scattering

We report a resonant inelastic X-ray scattering (RIXS) study of charge excitations in the two-leg ladder Sr₁₄Cu₂₄O₄₁. RIXS spectra at 1–5 eV are found to be dependent on temperature. An intraband excitation of the ladder, which appears as a continuum intensity below the Mott gap, decreases in intensity with temperature. Because the intraband excitation is related to the dynamics of doped holes in the ladder, its decrease of the intraband excitation is attributed to the reduction of the mobile holes in the ladder at low temperature.     

Photophysical properties and photocatalytic activities of bismuth molybdates under visible light irradiation

Aurivillius structure Bi(2)MoO(6) (BG: 2.70 eV) that is a low-temperature phase showed an intense absorption band in the visible light region and photocatalytic activity for O(2) evolution from an aqueous silver nitrate solution under visible light irradiation, among various bismuth molybdates (Bi(2)MoO(6), Bi(2)Mo(2)O(9), and Bi(2)Mo(3)O(12)) synthesized by solid-state and reflux reactions. Bi(2)Mo(3)O(12) (BG: 2.88 eV) also showed photocatalytic activity for O(2) evolution under full-arc irradiation of a Xe lamp (lambda > 300 nm). The photocatalytic activity of the Aurivillius structure Bi(2)MoO(6) prepared by the reflux method was dependent on the annealing temperature after the preparation. The crystallinity was the important factor for the activity. Calculation by the density functional method indicated that the conduction band of Aurivillius structure Bi(2)MoO(6) was made up of Mo 4d orbitals. It turned out that the visible-light absorption of this photocatalyst was due to the transition from the valence band consisting of O 2p orbitals to the conduction band. The corner-sharing structure of the MoO(6) octahedra contributed to the visible light response and the photocatalytic performance because excitation energy and/or photogenerated electron and hole pairs began to migrate easily in the Aurivillius structure.     

Polymerization of surface-active monomers. I. Micellization and polymerization of higher alkyl salts of dimethylaminoethyl methacrylate

Micellization of cationic salts of dimethylaminoethyl methacrylate (DMAEMA) quaternized with n-alkyl bromides such as octyl, lauryl, myristyl, and stearyl bromide and their polymerizations were investigated. The critical micelle concentration (cmc) in water at 25°C was determined by electrical conductivity and dye(azobenzene) solubilization methods and the relation log(cmc) = 1.46–0.31N was obtained, where cmc is in mmol L^?1 and N corresponds to carbon number of alkyl bromides used for the monomer preparations. All of these monomeric salts exhibited a high radical polymerizability in water and benzene. The polymerizations in water appeared to proceed with a higher rate with increasing a chain length of the alkyl moiety of the monomers and those in benzene gave the polymers with a remarkably high viscosity. The rate of polymerization of lauryl bromide salt in anisotropic solutions (in water and benzene) was exceedingly fast as compared with that in isotropic solution(in acetonitrile). All of the polymers obtained here were insoluble in water. Solubility characteristics of these monomers and polymers in other solvents were also presented. The reduced viscosity, in dimethylformamide and methanol, of poly(lauryl bromide salt) prepared in water increased with dilution but that for the polymer obtained in benzene exhibited an inverse concentration dependence. Some discussions were made on the peculiarities of the polymerizations of these monomers and the resulting polymers.     

Determination of trace elements in semiconductor materials by neutron activation analysis using the radioisotope addition technique

The determination of trace elements in highly activated matrix components was carried out by neutron activation analysis using the radioisotope addition technique. The method is based on the addition to the irradiated test sample of a radioisotope which is a diffeent nuclide of the element to be determined. After separation, the chemical yield is calculated from the radioactivity added and the element is determined by an ordinary technique. Twelve elements in indium phosphide and eight elements in gallium arsenide could be determined by the method.     

ESR study of99Tc/II/ complex formed by reduction of ammonium pertechnetate with ascorbic acid in concentrated hydrochloric acid

Paramagnetic⁹⁹Tc complex formed by the reduction of ammonium pertechnetate by ascorbic acid with excess sodium nitrite in concentrated hydrochloric acid was investigated by ESR technique. This complex had total electron spin S=1/2 and the obtained ESR parameters were: g_|=2.032, g=2.043, A_|=264 gauss and A=108 gauss. Based upon these data it was concluded that the formed species was low spin⁹⁹Tc/II/ complex.     

Range calculation of alpha-recoil atoms in some minerals using LSS-theory

Alpha-recoil ranges were calculated for fifteen interesting minerals, especially for naturally occurring alpha-emitters, on the basis of the simple LSS-theory. The ranges obtained from single decay process were represented as a comprehensive range expression in A units, as well as the physical ranges in g/cm² units. Furthermore, the total mean ranges concerning overall alpha-decaying members within each natural decay series, including the extinct neptunium series, have also been evaluated and tabulated. These calculated ranges can contribute to the interpretation of the widespread disequilibrium states in respective decay series in nature as well as in laboratory experiments.     

Determination of multielement in optical waveguide and standard reference materials by instrumental neutron activation analysis

Trace amounts of transition elements (Co, Cr, Cu, Fe, Mn and V) and other seven elements in optical waveguide samples were determined by INAA. The contents of impurities in ultra-pure materials are less than those of high-purity materials and of G.R. grade. The increase of contamination of trace transition elements and iridium from furnace or crucible are observed in the production of optical glass fibers. Up to seventeen elements were determined in five NBS biological standard reference materials: Oyster Tissue: SRM-1566, Brewers Yeast: SRM-1569, Spinach: SRM-1570, Orchard Leaves: SRM-1571 and Tuna Fish, and in four Japanese biological standard reference materials: Tea Leaves B&C, Pepperbush and Shark Meat. The analytical results in NBS and Japanese standard reference materials are in good agreement with published values and certified values by NBS.