Takayuki Kashiwakura

Photoemission Study of the Spectral Function of V2O3 in Relation to the Recent Quantum Monte Carlo Study

Photoelectron energy distribution curves near the Fermi level have been measured on V 2 O 3 above and below the critical temperature of the metal-insulator transition. In insulating phase, the band gap was found to be about 0.2 eV, which is consistent with the other experimental results. A clear Fermi edge, which becomes sharp at lower temperature, is found in the metallic phase. The 3d spectral feature is discussed in relation to the recent quantum-Monte-Carlo calculation. Resonant photoemission shows the hybridization effect is also important for the spectral feature.

Electronic Structure of CeB6 Studied by 3d XPS and High-Resolution 4d-4f Resonant Photoemission

Ce 3 d XPS and 4 d -4 f resonant photoemission spectra were measured and adopted to study the electronic structure of CeB 6 . Observed spectra were analyzed in terms of the single impurity Anderson model, which manifests the dense Kondo behavior of the electronic structure of CeB 6 . The low energy excitations which appear in photoemission spectra were discussed based on the 4 d -4 f resonant photoemission spectra measured with an energy resolution of 78 meV.

Soft X-ray resonant raman and resonant Auger spectra in SiK absorption edge

Abstract Si KLL Auger spectra and Kα x-ray emission spectra of Si and SiO 2 excited at the incident photon energies around the Si K edge were measured. For Si, evolution of the Auger spectra across the K edge and that of the Kα emission spectra are apparently the same. While for SiO 2 , a distinct difference between evolution of the Auger spectra and that of the x-ray emission spectra is found, i.e. no x-ray emission peak showing linear dispersion is observed above the edge.

Resonant 2 p →3 d Photoemission Measurement of MPS 3 (M=Mn, Fe, Ni)

Resonant 2 p →3 d photoemission (RPE) spectra in the valence band region of the transition-metal thiophosphates MPS 3 ( M=Mn, Fe, Ni) have been measured by using synchrotron radiation. These spectra show largely enhanced resonated profiles and spread over in the wide range (∼15 eV) at the incident photon energy of the transition-metal 2 p 3/2 absorption peak. Comparing the obtained spectra with the result of the cluster calculation of RPE spectra for transition-metal monoxides carried out by Tanaka and Jo, we argued the differences of the two parameters, charge transfer energy Δ and d - d Coulomb interaction energy U d d of these materials. It is suggested that MnPS 3 and FePS 3 are Mott-Hubbard type insulator with Δ > U d d , while NiPS 3 is a charge transfer type insulator with Δ < U d d .

The SK and PK polarized absorption spectra of layered thiophosphates MPS3 (M=Mn, Fe, Ni, Zn, Mg)

Abstract The Sue5f8 K and Pue5f8 K polarized absorption spectra were measured on the layered thiophosphates M PS 3 ( M =Mn, Fe, Ni, Zn, Mg) single crystals with linearly polarized synchrotron radiation light source. The Sue5f8 K polarization spectra indicate large polarization dependency especially on NiPS 3 . MnPS 3 and FePS 3 show the similar feature, while NiPS 3 shows different feature. No polarization dependency is observed in the spectra of MgPS 3 . The Pue5f8 K polarized absorption spectra also exhibit a small polarization dependency. From these spectra, the information about the p x,y and p z unoccupied states is obtained. Metal dependency is observed especially in the S p z spectra. It is revealed that the S p z state is largely mixed with the d orbitals of transition metal ion. Furthermore, we supposed that the P p states and the S p states are overlapped each other in the transition-metal thio-phosphates.

Comparison between resonant Lalpha emission spectra and resonant LMM Auger spectra of yttrium compounds.

Resonant Lalpha x-ray emission spectra (RXES) and resonant LMM Auger emission spectra (RAES) of Yttrium compounds were measured across YL(III) absorption threshold. When the incident photon energy is bellow the absorption threshold, only Raman scattering component is commonly observed in both spectra. Above the absorption threshold, Raman and normal Lalpha (or normal LMM Auger) emission peaks are observed in insulator samples. These spectral features are almost same in both RXES and RAES processes, except for the relative intensity ratio between these Raman peaks and normal Lalpha (or normal LMM Auger) emission peaks. Comparing these two spectra, useful information about the deexcitation of core hole can be obtained.

Resonant Auger spectra of Y, YF3 and YCl3 in Y LIII absorption edge

Y LMM resonant Auger spectra of Y metal, YF3 and YCl3 around Y LIII absorption edge have been measured by means of monochromatized synchrotron radiation. Y Lα resonant x-ray emission spectra which are competitive process of Auger transition are also measured for Y metal and YF3. In Y metal, both spectra exhibit linear dependence with incident photon energy below the absorption threshold. Similar linear dependence is found in YF3 below and above the threshold. The results are interpreted as the resonant Raman process following core-electron excitation.