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The electrochemical Ni deposition at a platinum electrode was investigated in a plating nickel bath in the presence and absence of ethylene glycol (EG) using fluorescence yield soft X-ray absorption spectroscopy (FY-XAS) in the Ni L2,3-edge and O K-edge regions under potential control. At ≤+0.35 V vs. the reversible hydrogen electrode (RHE), the electrochemical Ni deposition was detected by the Ni L2,3-edge FY-XAS in the presence of EG whereas almost no such event was observed in the absence of EG. A drastic decrease of FY-XAS intensities in the O K-edge region was also observed in the presence of EG at >+0.35 V vs. RHE, suggesting that the nano-/micro-structured Ni deposition initiated by the removal of water molecules occurs on the Pt electrode. The complex formation of Ni2+ with EG and the adsorption of EG on the Ni surface could play an important role in the Ni deposition. This study demonstrates that the in situ FY-XAS is a powerful and surface-sensitive technique to understand (electro)chemical reactions including polyol synthesis and electrocatalysis at solid–liquid interfaces.

The CeB6(001) single crystal used as a cathode in a low-emittance electron gun and operated at the free-electron laser facility SACLA was investigated using cathode lens electron microscopy combined with X-ray spectroscopy at SPring-8 synchrotron radiation facility. Multilateral analysis using thermionic emission electron microscopy, low-energy electron microscopy, ultraviolet and X-ray photoemission electron microscopy and hard X-ray photoemission spectroscopy revealed that the thermionic electrons are emitted strongly and evenly from the CeB6 surface after pre-activation treatment (annealing at 1500°C for >1 h) and that the thermionic emission intensity as well as elemental composition vary between the central area and the edge of the old CeB6 surface.

Adhesion is an interfacial phenomenon that is critical for assembling carbon structural composites for next-generation aircraft and automobiles. However, there is limited understanding of adhesion on the molecular level because of the difficulty in revealing the individual bonding factors. Here, using soft X-ray spectromicroscopy we show the physical and chemical states of an adhesive interface composed of a thermosetting polymer of 4,4’-diaminodiphenylsulfone-cured bisphenol A diglycidyl ether adhered to a thermoplastic polymer of plasma-treated polyetheretherketone. We observe multiscale phenomena in the adhesion mechanisms, including sub-mm complex interface structure, sub-μm distribution of the functional groups, and molecular-level covalent-bond formation. These results provide a benchmark for further research to examine how physical and chemical states correlate with adhesion, and demonstrate that soft X-ray imaging is a promising approach for visualizing the physical and chemical states at adhesive interfaces from the sub-mm level to the molecular level. Understanding adhesion mechanisms for polymer composites is challenging due to the bonded interface being buried. Here, soft X-rays are used to probe the chemical and physical nature of the interface, revealing multiscale factors that influence the adhesion mechanism and bond strength.

Using X-ray absorption spectroscopy (XAS), we investigated local chemical interactions in thermosetting epoxy resins for structural composites: N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane (...

A scanning soft X-ray spectromicroscope was recently developed based mainly on the photon-in/photon-out measurement scheme for the investigation of local electronic structures on the surfaces and interfaces of advanced materials under conditions ranging from low vacuum to helium atmosphere. The apparatus was installed at the soft X-ray beamline (BL17SU) at SPring-8. The characteristic features of the apparatus are described in detail. The feasibility of this spectromicroscope was demonstrated using soft X-ray undulator radiation. Here, based on these results, element-specific two-dimensional mapping and micro-XAFS (X-ray absorption fine structure) measurements are reported, as well as the observation of magnetic domain structures from using a reference sample of permalloy micro-dot patterns fabricated on a silicon substrate, with modest spatial resolution (e.g. ∼500 nm). Then, the X-ray radiation dose for Nafion® near the fluorine K-edge is discussed as a typical example of material that is not radiation hardened against a focused X-ray beam, for near future experiments.

The multi-ionization processes of Kr and Xe in the K-edge photon energy region were investigated using short-pulse x-rays and time-of-flight apparatus. The generation of Kr13+ ions in this photon energy region was observed for the first time. The distribution characteristics observed in the experiment, such as the production of Kr13+ ions, high production ratios of Kr4+, Kr5+, and Kr6+ ions, and the existence of a small peak for Kr8+, were quantitatively reproduced by the Monte Carlo simulation for the charge distribution of Kr ions following 1s of inner shell ionization. The highly charged ions were suppressed in the experiments compared with those in the simulation, probably owing to the inhibition of certain Coster-Kronig processes in the highly charged ions, which were not considered for analysis. The charge distribution of Xe ions following 1s of inner shell ionization was also investigated. A similar charge distribution was observed when the photon energy was located between the K and L edges. This is because the Xe 1s hole state mainly undergoes ultrafast relaxation to the 2p hole state owing to the strong dipole transition moment between the 1s and 2p states.

We report the direct evidence of valence fluctuation in the thermoelectric material Yb3Si5 by using synchrotron X-ray photoemission spectroscopy. The Yb 3d core level photoemission spectrum of a Yb3Si5 single crystal shows clear separation of the Yb2+ peak and Yb3+ multiplet peaks. From the spectral weight of each component, the mean valence of Yb ions is estimated to be +2.67 at 20 K. Furthermore, a Kondo resonance peak just below the Fermi energy is also observed by high-resolution soft X-ray photoemission spectroscopy, suggesting the valence fluctuating state in Yb3Si5.

The local electronic state of the N,N,N',N'-tetraglycidyl-4,4′-diaminodiphenylmethane epoxy resin cured with 4,4′-diaminodiphenylsulfone (TGDDM-DDS), one of model adhesive materials, was investigated by the O K-edge X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES). The total-electron-yield XAS spectra for TGDDM-DDS as a function of the X-ray dose exhibit the exponential-like decrease in the curing-derived pre-edge intensity due to the radiation damage. The quantitative analysis on the pre-edge intensity with respect to the X-ray dose enables the determination of the critical absorbed dose for the chemical change on TGDDM-DDS as 3.83 ± 0.01 MGy at 300 K. By using resonant XES with the well-focused X-ray beam, we found that (i) the charged-particle equilibrium exists for the soft X-rays in the range of at least 0.001–0.847 mm2 beam spot and that (ii) the half of the critical absorbed dose can be regarded as the limit indicator for the non-destructive chemical-state characterization on resinous adhesive materials and interfaces using soft X-rays.

The CeB

The competition between magnetic shape anisotropy and the induced uniaxial magnetic anisotropy in the heterojunction between a ferromagnetic layer and a ferroelectric substrate serves to control magnetic domain structures as well as magnetization reversal characteristics. The uniaxial magnetic anisotropy, originating from the symmetry breaking effect in the heterojunction, plays a significant role in modifying the characteristics of magnetization dynamics. Magnetoelastic phenomena are known to generate uniaxial magnetic anisotropy, however, the interfacial electronic states that may contribute to the uniaxial magnetic anisotropy have not yet been adequately investigated. Here, we report experimental evidence concerning the binding energy change in the ferromagnetic layer/ferroelectric substrate heterojunction using X-ray photoemission spectroscopy. The binding energy shifts, corresponding to the chemical shifts, reveal the binding states near the interface. Our results shed light on the origin of the uniaxial magnetic anisotropy induced from the heterojunction. This knowledge can provide a means for the simultaneous control of magnetism, mechanics, and electronics in a nano/microsystem consisting of ferromagnetic/ferroelectric materials.

The dissociation and ionization dynamics of CF3I and CH3I molecules were investigated using a pump-and-probe technique that employs a soft X-ray free-electron laser SACLA in Japan. First, time-resolved inner-shell photoelectron spectroscopy was employed to observe the ultrafast reaction of CF3I by monitoring iodine 4d electrons. The change of I 4d state observed in the photoelectron spectra is found to occur with a rising time τ of about 40 fs after a pump laser pulse, which is faster than that observed when an ultrafast gas-phase electron diffraction technique is employed. This implies that the inner-shell photoelectron spectroscopy is more sensitive to the potential surface near the Franck–Condon region. Second, a strong laser intensity at 266 nm, corresponding to a power density of 1.9 × 1014 W/cm2, can easily ionize CH3I molecule via multiphoton ionization processes, and the time dependence of the valence photoelectron spectra clearly show that, at the picosecond timescale, this pump laser pulse causes spectral peaks to shift due to space-charge effects in response to the large amount of ions generated. Thus, the soft x-ray free-electron laser can be a useful tool to investigate not only the dynamical process of molecular dissociation but also the ionization process through the shift in the peak of the photoelectron spectra.

The $LMM$ Auger spectra of krypton are measured using the photon energies $h\ensuremath{\nu}=1709$ eV, 1792 eV, 1950 eV, and 13 keV. This approach allows separating the contributions from the various core holes ${L}_{1}, {L}_{2}$, and ${L}_{3}$. Previously unobserved transitions are presented. Complementary theoretical work is performed allowing the assignment of the spectral features. The ${L}_{2,3}Y\text{\ensuremath{-}}MMY$ ($Y={M}_{4,5},{N}_{1,2,3})$ Auger transitions of ${\mathrm{Kr}}^{2+}$ formed via Coster-Kronig Auger decay of the core holes ${L}_{1}$ and ${L}_{2}$ are also investigated. These spectra comprise about 4000 and 13 000 transitions, respectively, so that only general statements on the assignment, such as the configurations involved in the transitions, can be given.

We study the electronic structure of single crystal $1T\ensuremath{-}{\mathrm{TiSe}}_{2}$ using temperature ($T$)-dependent soft x-ray photoemission spectroscopy (PES) and natural circular dichroism (NCD) across the charge-density-wave (CDW) transition at ${T}_{\mathrm{cdw}}\ensuremath{\sim}200$ K. We investigate detailed changes in energy positions and widths of the Ti $2p$ and Se $3d$ core-level spectra across ${T}_{\mathrm{cdw}}$. The Ti $2p\ensuremath{-}3d$-resonant PES shows a clear Ti $3d$ character two-hole correlation satellite in the valence band. A Cini-Sawatzky analysis indicates an effective attractive two-hole Coulomb interaction energy ${U}_{dd}$ =\ensuremath{-}1.3 eV. This attractive Coulomb energy is significantly larger than the known energy scale of excitonic correlations ($l$ 100 meV) in $1T\ensuremath{-}{\mathrm{TiSe}}_{2}$. On-resonant $T$-dependent measurements indicate that the strongly hybridized Ti $3d$-Se $4p$ bands show increased hybridization in the CDW phase. On-resonant valence band spectra show a finite, possibly experimental geometry-related NCD of the states at and near the Fermi level which do not show $T$ dependence across ${T}_{\mathrm{cdw}}$. Given the presence of excitonic effects and the periodic lattice distortion, our results suggest that theoretical models need to take into account the attractive Coulomb interaction and hybridization changes for a complete understanding of the CDW in $1T\ensuremath{-}{\mathrm{TiSe}}_{2}$.

Electronic relaxation of atomic Kr below and above the $1s$ ionization threshold is investigated experimentally using hard x-ray photoelectron spectroscopy. The experimental results are interpreted with the aid of relativistic Dirac-Fock calculations. The $1s$ orbital core-hole lifetime is extracted and the satellite's structures accompanying the photoelectron main line are assigned. Auger spectra recorded below and above the $K$ edge are also investigated. In particular, the Auger cascade originating from vacancies of different origin in the $L$ shell is analyzed in great detail. Competition between radiative $KL$ versus nonradiative $KLL$ Auger emission is emphasized.

We measured the Kr photoelectron spectrum in the region close to the $3p$ ionization threshold. Our high-resolution measurements allowed a clear observation of spectral structures due to electron correlation effects. Analysis based on relativistic multiconfiguration calculations could explain these observed peaks as due to strong configuration interactions between the $3{p}^{\ensuremath{-}1}$ state and $3{d}^{\ensuremath{-}2}nl$ states. Calculated and experimental data for peak assignments and intensity distributions are in good agreement. In addition, we measured the anisotropy parameter $\ensuremath{\beta}$, which also agreed well with theory. These findings provide a detailed view of strong configuration interactions between the $3{p}^{\ensuremath{-}1}$ and $3{d}^{\ensuremath{-}2}nl$ inner-shell hole states.

An experimental and computational investigation of the space-charge effects occurring in ultrafast photoelectron spectroscopy from the gas phase is presented. The target sample CF$_3$I is excited by ultrashort (100 fs) far-ultraviolet radiation pulses produced by a free-electron laser. The modification of the energy distribution of the photoelectrons, i.e. the shift and broadening of the spectral structures, is monitored as a function of the pulse intensity. The experimental results are compared with computational simulations which employ a Barnes-Hut algorithm to calculate the effect of individual Coulomb forces acting among the particles. In the presented model, a survey spectrum acquired at low radiation fluence is used to determine the initial energy distribution of the electrons after the photoemission event. The spectrum modified by the space-charge effects is then reproduced by $N$-body calculations that simulate the dynamics of the photoelectrons subject to the individual mutual Coulomb repulsion and to the attractive force of the positive ions. The employed numerical method accounts for the space-charge effects on the energy distribution and allows to reproduce the complete photoelectron spectrum and not just a specific photoemission structure. The simulations also provide information on the time evolution of the space-charge effects on the picosecond scale. Differences with the case of photoemission from solid samples are highlighted and discussed. The presented simulation procedure, although it omits the analysis of angular distribution, constitutes an effective simplified model that allows to predict and account for space-charge effects on the photoelectron energy spectrum in time-resolved photoemission experiments with high-intensity pulsed sources., 21 pages, 5 figures, 1 table

Hard X-ray photoelectron spectroscopy (HAXPES), aided by the progress of synchrotron radiation (SR) beamlines as well as the development of state-of-the-art electron analyzers, has established a fi...

Differences in postcollision interaction (PCI) effects on Kr L_{3}M_{4,5}M_{4,5} Auger electron spectra were observed, depending on whether the initial photoionization occurred slightly above the K threshold or slightly above the L_{3} threshold. For the former, KL fluorescence emission most likely happens and then Auger processes due to the L_{3} hole follow. The time delay due to fluorescence causes a reduced shift of the Auger peak and tailing toward lower energy, since the Auger overtaking of the photoelectron happens later in time and at a location farther away from the ionic core, compared to the case for the simple one-step L_{3}M_{4,5}M_{4,5} Auger decay after L-shell photoionization. Time-dependent theory for PCI in multistep processes agrees well with experiment, illustrating the effect as an internal clock for the time-sequence of the dynamical process.

Hard X-ray electron spectroscopic study of iodine 1s and 2s photoionization of iodomethane (CH3I) and trifluoroiodomethane (CF3I) molecules is presented. The experiment was carried out at the SPring-8 synchrotron radiation facility in Japan. The results are analyzed with the aid of relativistic molecular and atomic calculations. It is shown that charge redistribution within the molecule is experimentally observable even for very deep levels and is a function of the number of electron vacancies. We also show that the analysis of Auger spectra subsequent to hard X-ray photoionization can be used to provide insight into charge distribution in molecules and highlight the necessity of quantum electrodynamics corrections in the prediction of core shell binding energies in molecules that contain heavy atoms.

The unique characteristics of an acetic acid/1-methylimidazole (1-MI) mixture, showing higher electrical conductivity than either neat acetic acid or neat 1-MI, yet consisting of electrically neutral molecules, are reported. We have applied soft X-ray spectroscopy to reveal the electronic states of acetic acid in the acetic acid/1-MI mixture at various mole fractions of acetic acid (χHOAc). The results show that the amount of acetic acid monomer increases in the region of especially high electrical conductivity and the amount of complex of acetic acid and 1-MI formed by sharing molecular orbitals increases in the low electrical conductivity region. There is a little amount of acetic acid monomer in the low electrical conductivity region because the complex inhibits acetic acid from creating its monomer. These results suggest the possibility that the acetic acid monomer is related to electrical conduction.

International audience; We have recently initiated hard x-ray photoelectron spectroscopy experiments on heavy atoms and heavy-element containing molecules in gas phase by using synchrotron radiation up to 35 keV at SPring-8 undulator beamlines. We have successfully measured deep inner-shell photoelectron spectra, as well as L-MM and M-NN Auger electron spectra excited below and above the K-edge of heavy elements. Target specimens utilized for the preliminary experiments are Ar, Kr and Xe atoms, and also iodine in iodomethane (CH 3 I) and trifluoroiodomethane (CF 3 I) molecules, respectively. We show some selected results on the extracted core-hole lifetime broadenings for the iodine 1s core level of the CH 3 I molecule and also for the Xe 2s, 2p core levels, to compare with theoretical values. The L-MM Auger electron spectra of Kr recorded at 13 and 16.6 keV excitation energies are also shown as typical examples, and the spectrum measured above the K-edge, i.e. 14.327 keV, is analyzed based on theoretical calculations using the Hartree-Fock method. As a result, we give a tentative assignment for the double-core-hole hyper-satellite LL-LMM Auger transitions of the Kr atom.

Carbon 1s photoelectron angular distributions of an iodomethane molecule were measured relative to the recoil-frame determined by the momentum correlation between I+ and CH3+ at photoelectron energies of 3, 6.1, and 12 eV. The energy dependent behavior of the recoil-frame photoelectron angular distributions is reproduced reasonably well by the time-dependent density functional theory with B-spline methods. We discuss potential applications of the fully differential photoelectron angular distribution measurements in the molecular frame to three-dimensional molecular structural determinations identifying the directions and lengths of the bonds.

International audience; Hard X-ray electron spectroscopic study of iodine 1s and 2s photoionization of iodomethane (CH3I) and trifluoroiodomethane (CF3I) molecules is presented. The experiment was carried out at the SPring-8 synchrotron radiation facility in Japan. The results are analyzed with the aid of relativistic molecular and atomic calculations. It is shown that charge redistribution within the molecule is experimentally observable even for very deep levels and is a function of the number of electron vacancies. We also show that the analysis of Auger spectra subsequent to hard X-ray photoionization can be used to provide insight into charge distribution in molecules and highlight the necessity of quantum electrodynamics corrections in the prediction of core shell binding energies in molecules that contain heavy atoms.

We report a comparative study of the electronic structure of the compounds LaTe and CeTe, both of which crystallize in the rock salt structure. LaTe is a paramagnetic metal while CeTe is known to exhibit anomalous Kondo-like transport behaviour and undergoes a transition to a complex magnetically ordered state at low temperature ( T N = 2.2 K). We carry out hard X-ray photoelectron spectroscopy (HAXPES) of the core-levels and valence band of LaTe and CeTe at T = 20 K, in order to characterize their intrinsic electronic structure, and to address the role of Kondo effect on the electronic structure of CeTe. The bulk sensitive core level HAXPES spectra show evidence of screened features in the La 3 d and Ce 3 d states mixed with plasmon features. From a careful analysis of the Te, La and Ce derived core levels, we separate out the respective origins of the satellites and show that CeTe indeed exhibits definitive but weak f 0 and f 2 satellites due to Kondo screening, in addition to the main f 1 peak. The comparison of the valence band spectra of CeTe obtained using HAXPES and soft X-ray PES clearly identifies the Ce 4 f derived features. Resonant photoelectron spectrosocopy across the Ce 3 d − 4 f threshold confirms the Ce 4 f 1 final state at the Fermi level, corresponding to the tail of the Kondo resonance feature which occurs above the Fermi level, while the Ce 4 f 0 final state feature is observed at a binding energy of 2.4 eV. The 4 f 0 and 4 f 1 final states show giant resonances compared to the off-resonant spectra. However, in contrast to typical Kondo systems, the tail of the Ce 4 f 1 Kondo resonance at the Fermi level is relatively suppressed compared to the Ce 4 f 0 feature, which exhibits an unusually strong resonance enhancement. The results are indicative of a weakened Kondo effect which favours the magnetically ordered ground state in CeTe.

We have applied a recently developed scanning soft x-ray spectromicroscope to characterize the buried multi-layered micro-structure by means of microprobe x-ray fluorescence (μXRF) analyses. We could successfully visualize single element maps of O and Fe contained in a buried 500-μm square test-pattern made of SiO2 and Ni81Fe19 (permalloy) beneath 30-nm thick Au coating. For their chemical-state analyses, we measured O Kα and Fe Lα x-rays emitted from the buried micro-structure using a soft x-ray microprobe to explore the x-ray absorption spectroscopy (XAS) spectra of O and Fe contained in a local area by partial fluorescence yield spectroscopy.

In this work, X-ray absorption spectroscopy (XAS) and site-selective X-ray emission spectroscopy (XES) were used to measure the oxygen K-edge (OC=O,1s and OCO−,1s) of oxalic acid, with theoretical calculations performed to reproduce the spectra observed. Structure sampling of a cluster model was performed using an ab initio molecular dynamics trajectory. Relative XES intensities from core-hole excited state dynamics simulations were calculated using density functional theory (DFT). It was found that the theoretical X-ray absorption and emission spectra well reproduced the experimental spectra and showed a resonant effect between COOH functional groups which is absent in monocarboxylic acids.

Sb deposition and reaction on In/Si(111) were investigated by low-energy electron microscopy, low-energy electron diffraction, synchrotron radiation micro X-ray photoelectron spectroscopy and synchrotron radiation X-ray photo-emission electron microscopy. The Sb deposition process strongly depends on the initial In/Si(111) phases such as √3 × √3, √31 × √31 and 4 × 1. On the In/Si(111) surface where two phases co-exist, the diffusion of In atoms, which are released by the attack of Sb, modifies the deposition and reaction process of Sb. On a mixed In/Si(111) √31 × √31 + 4 × 1 surface, an InSb(111) 2 × 2 structure with elongated domains initially forms along steps. Then In atoms are replaced by Sb atoms and InSb(111) 2 × 2 transforms into Sb/Si(111) 2 × 1 by further reaction with Sb atoms. Here, the existence of the 4 × 1 phase promotes the formation of larger InSb(111) 2 × 2 domains.

MoS2, Ni-doped MoS2, and Ni-doped MoS2/Al2O3 were synthesized by using thiourea as an organosulfur source with simple and low cost methodology to convert phenol, a model compound of lignin biomass into cyclohexane via catalytic hydrodeoxygenation (HDO). As-synthesized catalysts were characterized by X-ray diffraction, thermal gravimetric analysis, N2 sorption, transmission electron microscopy, and X-ray absorption near-edge structure. The phenol conversion was achieved better in semi-amorphous MoS2 than the crystalline one. In addition, all developed MoS2 showed high selectivity toward HDO of phenol than hydrogenation of phenol, leading to ~ 90% of cyclohexane selectivity in Ni-doped MoS2.

Spin-chiral domain structures near a cleaved crystal face of a magnetoelectric helimagnet, Ba0.5Sr1.5Zn2Fe12O22, were examined after various magnetic and electric field-cooling procedures by means of the scanning resonant X-ray microdiffraction technique using circularly polarized X-rays. We have found that the application of a magnetic field (1–2 k Oe) during the field-cooling procedure stabilizes one of the handedness among the two spin-chiral states (left- or right-handed screw structure) and makes nearly a single spin-chiral domain in the vicinity of the cleaved crystal face. However, it makes the degree of the spin chirality spatially inhomogeneous even within a domain. We discuss the observed field-cooling effect in terms of possible formation of spin-chiral domains with “stripe-type” domain walls accompanied by randomly-distributed ferromagnetic islands.

We study the electronic structure of HgBa_{2}Ca_{2}Cu_{3}O_{8+δ} (Hg1223; T_{c}=134 K) using photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS). Resonant valence band PES across the O K edge and Cu L edge identifies correlation satellites originating in O 2p and Cu 3d two-hole final states, respectively. Analyses using the experimental O 2p and Cu 3d partial density of states show quantitatively different on-site Coulomb energy for the Cu site (U_{dd}=6.5±0.5 eV) and O site (U_{pp}=1.0±0.5 eV). Cu_{2}O_{7}-cluster calculations with nonlocal screening explain the Cu 2p core level PES and Cu L-edge XAS spectra, confirm the U_{dd} and U_{pp} values, and provide evidence for the Zhang-Rice singlet state in Hg1223. In contrast to other hole-doped cuprates and 3d-transition metal oxides, the present results indicate weakly correlated oxygen holes in Hg1223.

International audience; Xe 1s photoelectron spectra were measured at SPring-8, Japan. The core-hole lifetime broadening was found to be 9.6 eV, yielding a lifetime of ∼68 as. The amount of radiative versus nonradiative decay was assessed by recording Auger LMM spectra below and above the K edge. Below the K edge, L vacancies are produced only by direct photoionization, while above the K edge some of these vacancies are mainly produced by KL emission following 1s photoionization. Due to the dipole selection rule for x-ray emission, the dominant role of the KL relaxation process is rather directly observed.

We study the electronic structure of Tsai-type cluster-based quasicrystalline approximants, ${\mathrm{Au}}_{64}{\mathrm{Ge}}_{22}{\mathrm{Yb}}_{14}$ (AGY-I), ${\mathrm{Au}}_{63.5}{\mathrm{Ge}}_{20.5}{\mathrm{Yb}}_{16}$ (AGY-II), and ${\mathrm{Zn}}_{85.4}{\mathrm{Yb}}_{14.6}$ (Zn-Yb), by means of photoemission spectroscopy. In the valence band hard x-ray photoemission spectra of AGY-II and Zn-Yb, we separately observe a fully occupied $\mathrm{Yb} 4f$ state and a valence fluctuation derived Kondo resonance peak, reflecting two inequivalent Yb sites, a single Yb atom in the cluster center and its surrounding Yb icosahedron, respectively. The fully occupied $4f$ signal is absent in AGY-I containing no Yb atom in the cluster center. The results provide direct evidence for a heterogeneous valence state in AGY-II and Zn-Yb.

Resonant X-ray diffraction (RXD) uses X-rays in the vicinity of a specific atomic absorption edge and is a powerful technique for studying symmetry breaking by motifs of various multipole moments, such as electric monopoles (charge), magnetic dipoles (spin) and electric quadrupoles (orbital). Using circularly polarized X-rays, this technique has been developed to verify symmetry breaking effects arising from chirality, the asymmetry of an object upon its mirroring. Chirality plays a crucial role in the emergence of functionalities such as optical rotatory power and multiferroicity. Here we apply spatially resolved RXD to reveal the helix chirality of Dy 4f electric quadrupole orientations and its domain structure in DyFe3(BO3)4, which shows a reversible phase transition into an enantiomorphic space-group pair. The present study provides evidence for a helix chiral motif of quadrupole moments developed in crystallographic helix chirality.

A photoemission electron microscope (PEEM) system has been newly installed at the soft X-ray undulator beamline (BL17SU) of SPring-8 to realize time-resolved nanospectroscopy for the local transient electronic structures of advanced materials. This PEEM is a versatile machine composed of an electrostatic lens system and is intended for use in specific experiments such as time-resolved measurements. Pump–probe measurements in tandem with a femtosecond pulsed-laser system and an X-ray chopper are now readily available.