Hirofumi Oohashi

The effect of Coster?Kronig transitions on the anisotropy of x-ray emission following Au L-shell photoionization

We studied the effect of Coster?Kronig transitions between L subshells on the anisotropy of x-rays emitted from Au ions following L-shell photoionization. The angular distribution of L x-rays was measured at incident photon energies selected above the threshold energy for each subshell with a crystal spectrometer. The experimental results show that the Coster?Kronig transitions have a small influence on the anisotropy of x-ray emission. Simple model estimations for the effect of the vacancies of the M or N shells on the anisotropy of x-ray emission following the Coster?Kronig transitions were made. The calculated results also indicate a small effect.

Intermediate-Valence Behavior of YbCu5-xAlx around Quantum Critical Point Measured by Resonant Inelastic X-ray Scattering at Yb L3 Absorption Edge

An x-ray spectroscopy study was performed for YbCu 5- x Al x ( x = 0.0–2.0) using high-resolution partial-fluorescence yield (PFY) and resonant inelastic x-ray scattering (RIXS) at the Yb L 3 absorption edge. From a careful analysis of the PFY and RIXS spectra, the mean-valence of Yb was estimated and is found to increase quite rapidly for compositions between 0 ≤ x ≤1.0, indicating strong intermediate-valence behavior. The mean valence continues to increase gradually with x and becomes nearly trivalent for x = 2.0. Our results, however, reveal that valence fluctuation occurs even at x =1.5, for which non-Fermi liquid quantum critical behavior is known. The valence evolution cannot be explained solely in terms of chemical pressure effects. The study suggests the role of valence-coupled spin fluctuations for the quantum critical behavior.

Resonant inelastic X-ray scattering of EuNi2(Si1-xGex)2 and Eu2O3 at Eu L3 absorption edge

Bulk sensitive spectroscopies were performed for mixed valent compounds EuNi 2 (Si 1- x Ge x ) 2 as a function of x , and Eu-sesquioxide (Eu 2 O 3 ), using techniques of high-resolution partial-fluorescence yield (PFY) and resonant inelastic x-ray scattering (RIXS) at the Eu L 3 absorption edge. The evolution of mean-valency as a function of chemical composition x in EuNi 2 (Si 1- x Ge x ) 2 shows a drastic change between x =0.5 and 0.7. The experimental results also show a small amount of mixed valency for the end members, i.e., x =1 and 0 samples are also mixed valent. Single-impurity Anderson model calculations show good agreement with the PFY and RIXS experimental results, and thus provide a consistent set of electronic structure parameters. The composition controlled drastic change in mean-valence between x =0.5 and 0.7 is derived from a large hybridization change, consistent with the Kondo volume collapse picture.

Threshold excitation in fe kα3,4 satellites

Fe Kα3,4 satellite spectra are investigated using a Johann-type spectrometer at the BL15XU undulator beam line, SPring-8. The intensity of the Kα3,4 satellite relative to the Kα1 emission line is found to increase asymptotically with excitation energy up to 9000 eV, almost saturating at 10 000 eV. The satellite threshold energy is found to be 7882 ± 14 eV. This corresponds to the ionization energy of Fe 1s + 2p*, where * indicates that the value is from the Z + 1 approximation. The appearance of a small peak around the [1s2s] double ionization energy suggests that the satellite intensity with the excitation energy can be increased not only by the formation of the 2p spectator holes, but also by a combination of the [1s2s] resonance and [2s2p] Coster–Kronig transition.

Charge-Transfer Satellite in Ce@C82 Probed by Resonant X-ray Emission Spectroscopy

The electronic structure of metallofullerene Ce@C 82 is probed by resonant x-ray emission spectroscopy at the Ce L 3 absorption edge. We observed a satellite structure in x-ray absorption and resonant emission spectra for Ce@C 82 , which, we show, corresponds to the charge transfer induced by the core–hole potential in the final state, similarly to Pr@C 82 . This charge-transfer satellite may be a common feature in metallofullerenes. The temperature dependence of the electronic structure is also investigated.

High‐Resolution Anti‐Parallel Double‐Crystal Spectrometer at BL15XU in SPring‐8

A simple double‐crystal spectrometer with an anti‐parallel setting was developed in the third generation synchrotron facility BL15XU, SPring‐8. This is derived by modifying the commercial RIGAKU Spectrometer (3580E). Although the resolving power of the two‐crystal x‐ray spectrometer is largely dependent on the perfection of the crystals, the x‐ray spectrometer secures high resolving power, intensity, and reproducibility. This system is convenient for the experiment of Resonant Inelastic X‐ray Scattering (RIXS). As an example, RIXS data of several elements in ferroelectric materials LiTaO3 and BaTiO3 and XAS spectra of Cu metal and Cu oxide are presented.

Satellites hidden by diagram lines in heavy elements Ir, Pt, Au

Hidden satellites due to Coster–Kronig transitions have a characteristic threshold energy in their appearance and hence can be identified by looking at spectra at either side of the threshold. To investigate the hidden satellites, we measured Lβ2,3,15 spectra of Ir, Pt and Au below and above the L1 edge. The measured spectra were normalized using Lβ1 spectra. The existence of hidden satellites was confirmed by observing the differences between the normalized spectra above and below the L1 edge.

Determination of 78Pt L3–N4 transition energy using threshold excitation in SPring-8

The spectral width and the energy of the Pt Lβ15(L3–N4) emission line have been determined using a Johann-type spectrometer with tunable photon energies around the L1 threshold. The Pt Lβ15 line has been found to have a FWHM of 9.57(17) eV and a transition energy of 11233.59(29) eV and its values are compared with the ones calculated by the GRASP code.

Evolution on Kα in Fe and Lβ satellites in Au in SPring‐8

With the advent of the third generation synchrotron radiation, we can perform experiments on the threshold behavior of the satellites including the excitation dynamics in atoms. Especially, x‐ray emission spectroscopy is a suitable tool to study the satellites on the electron correlation. The contributions of direct ionization, i.e, the shake‐off process in Fe and indirect ionization of Coster‐Kronig transition in Au have not been investigated to the x‐ray emission spectra yet. We present the contribution of the spectator holes to the processes around the threshold.