Tokuo Matsukawa

XANES and EXAFS studies on K-shell absorption in K1−xNaxCl solid solutions

Abstract X-ray absorption measurements were made for Na K-edge on K1−xNaxCl solid solutions at room and at low temperatures using synchrotron radiation. The prominent peak can be assigned as the exciton associated with intra-ionic transition of Na+ ion. The small structure appearing in the edge is assigned as the exciton associated with the dipole-forbidden s-s transition. From the analysis of EXAFS spectra, it was concluded that the first shell distance around the sodium ion in the solid solution holds the value of the pure NaCl, and is insensitive to the concentration of NaCl in KCl.

Valence-Band X-Ray Photoemission of PbI2 and CdI2

The valence-band spectrum in X-ray photoemission of PbI 2 does not agree with the reported results of energy-bend calculations, which predict that the highest valence band consists mainly of the 6 s state of Pb ++ and is isolated from other component-bands. Weak lines are found about 6 eV below the valence-band lines in various Pb-compounds. It is suggested that either the weak line in PbI 2 corresponds to the 6 s level of Pb ++ or the upper part of the valence band has both the 6 s character of Pb ++ and the 5 p character of I - appreciably. The valence-band spectrum of CdI 2 resembles the valence-band spectrum of PbI 2 . The data of the chlorides and bromides of Pb and Cd are also presented.

Full Multiple-Scattering Approach to Na K-Edge XANES of NaCl-KCl Mixed Crystal

In this work we studied the Na K-edge XANES spectra of pure NaCl crystal and NaCl–KCl mixed crystal measured by Murata et al. to clarify the geometric and electronic structure around X-ray absorbing atoms by use of the short-range order full multiple scattering calculation. The changes observed in the experimental XANES for the increase of KCl concentration are qualitatively explained by assuming that in a very small scale Nail and KCl grains are to be in contact with each other. We also found that the Na–Cl distance in the boundary region remains nearly the same as in NaCl crystal. The net charge on Na ion in pure NaCl crystal is also estimated and found to be slightly smaller than that in NaF crystal.

Point Defects in Cubic Boron Nitride after Neutron Irradiation

The production of point defects induced by reactor neutrons and the thermal behavior of defects in sintered cubic boron nitride are investigated using the optical absorption and electron spin resonance (ESR) methods. A strong structureless absorption over the visible region was observed after fast neutron irradiation to a dose of 5.3×1016 n/cm2 (E>0.1 MeV) at 25 K. This specimen also shows an ESR signal with g-value 2.006±0.001, which can be tentatively identified as an electron trapped in a nitrogen vacancy. On examination of the thermal decay of the signal, the activation energy for recovery of the defects was determined to be about 1.79 eV.

The K-Absorption Spectra of FeS2, CoS2 and NiS2

The K-absorption spectra of sulfur and metal ions in a series of transition-metal disulfides MS2 (M=Fe, Co, Ni) have been measured with two-crystal spectrometers. Considerable differences in the profiles are observed between the spectra of metal and sulfur ions, while the respective spectra are alike among different compounds. Consideration about the similarity and the dissimilarity in the spectral features suggests that the simple energy-band picture or the simple molecular-orbital picture is not adequate for the explanation of the observed spectra.

Property of Radiation-Induced Defects in Germanium Single Crystals

To study the property of defects produced in high-purity and p-type germanium single crystals by thermal neutron, fast neutron or electron irradiation, annealing experiments on irradiated samples were performed with electrical measurements and a deep-level transient spectroscopy technique. The annealing behavior of defects produced by the recoil energy of (n, γ) reaction in a high-purity sample irradiated with thermal neutrons indicates that interstitial arsenic atoms and interstitial gallium atoms are restored to lattice sites during annealing in the temperature range from 180° C to 240° C and that from 260° C to 340° C, respectively. The defects produced by neutron irradiation were annihilated by annealing for 20 min at 380° C. Two hole traps located at E v+0.32 eV and E v+0.53 eV were formed in a high-purity crystal by electron irradiation.

Cationic Core Excitons in NaBr and MgBr2

Na- K and Mg- K soft X-ray absorption spectra have been measured with high resolulion using synchrotron radiation. The results on NaBr and MgBr 2 are presented. The spectral features at the absorption edges are shown to be common in character among the Na- K and the Mg- K spectra. A tentative assignment of the structures is presented. They are ascribed to cationic excitons associated with 1 s to 3 s and to 3 p transitions in the metal ions.

X-Ray K Absorption Edge Structures of Chlorine Ion in [CoCl2(en)2]NO3, [CoCl2(en)2]Cl and [Co(en)3]Cl3 ·3H2O

X-ray K absorption edge structures of chlorine ion in trans-[CoCl 2 (en) 2 ]NO 3 , trans-[CoCl 2 (en) 2 ]Cl and [Co(en) 3 ]Cl 3 ·3H 2 O are measured with a high-resolution vacuum two-crystal spectrometer. The spectra, except that of [Co(en) 3 ]Cl 3 ·3H 2 O having no ligand Cl - ion, show an extremely narrow absorption line at the absorption threshold. All of the spectra show a broad absorption band extending to the higher energy region of the narrow absorption line. It is found that a characteristic of the respective spectra depends on the different chemical states between the cobalt and chlorine ions. The result is interpreted on the basis of molecular orbital theory.

Soft X-Ray Small-Angle Scattering by Polystyrene Latexes Using Synchrotron Radiation

Small-angle scattering of soft X-rays by polystyrene latex spheres was studied using the synchrotron radiation from the electron synchrotron operated at about 1 GeV at the Institute for Nuclear Study, University of Tokyo. The exposure time required to make three smallest-angle diffraction peaks visible on a photographic plate was 2 min with the soft X-rays (46.8 A) of the synchrotron radiation, compared to 400 min with the CKα radiation (44.8 A) from the X-ray tube operated at 3 kV ×50 mA. The diffraction patterns were so distinct that inter-particle interference functions could be derived with four diffraction peaks. Experimental results as a whole suggest that soft X-rays in the synchrotron radiation will be very useful in studying two-dimensional structures of thin organic materials with the thickness of microns or submicrons.

Resonant photoemission in Ce2Zn17 with stable trivalent valence

Abstract We report resonant photoemission spectra of Ce 2 Zn 17 and La 2 Zn 17 at room temperature and low temperature. The double-peaked structure arising from the 4 f state is found in photoemission spectra even for the stable trivalent Ce compound. We discuss that it is necessary to take account of energy dependence of hybridization matrix element exactly.