Hiroshima Synchrotron Radiation Center Research Articles

Observation of the Liquid-Liquid Phase Separation of FUS-LC Using Vacuum-Ultraviolet Circular Dichroism Spectroscopy.

To reveal the structural mechanism by which the low-complexity domain of the fused in sarcoma protein (FUS-LC) mediates liquid-liquid phase separation (LLPS), we conducted a vacuum-ultraviolet circular dichroism (VUV-CD) spectroscopic study, a technique to analyze the secondary structures of proteins. The VUV-CD measurements were performed at the BL12 VUV-CD station at the Hiroshima Synchrotron Radiation Center (HiSOR) in Japan. CD spectra were measured between 180 and 260 nm while controlling the temperature of samples from 37°C to 5°C to obtain the LLPS of FUS-LC. The CD spectrum obtained at 37°C exhibited a large negative peak at 195 nm and a small negative shoulder near 220 nm. The peak intensity around 195 nm decreased as the sample temperature decreased. The spectral changes originated from the LLPS formation.

Design study of an electron storage ring for the future plan of Hiroshima Synchrotron Radiation Center

We present the latest result from the design study for the future plan of Hiroshima synchrotron radiation center (HSRC). The design goal is the energy of around 500 MeV, the circumference shorter than 50 m and the emittance smaller than 10 nm with straight sections for undulators more than 4. We have selected the lattice structure similar to ASTRID 2 compact light source in Aarhus University, Denmark.

Rotatable high-resolution ARPES system for tunable linear-polarization geometry

A rotatable high-resolution angle-resolved photoemission spectroscopy (ARPES) system has been developed to utilize tunable linear-polarization geometries on the linear undulator beamline (BL-1) at Hiroshima Synchrotron Radiation Center. By rotating the whole ARPES measurement system, the photoelectron detection plane can be continuously changed from parallel to normal against the electric field vector of linearly polarized undulator radiation. This polarization tunability enables us to identify the symmetry of the initial electronic states with respect to the mirror planes, and to selectively observe the electronic states based on the dipole selection rule in the photoemission process. Specifications of the rotatable high-resolution ARPES system are described, as well as its capabilities with some representative experimental results.

Quasi-Periodic Variably Polarizing Undulator at HiSOR

A 1.8-m-long 78-mm-period quasi-periodic APLPE-II undulator was installed in the 700-MeV HiSOR storage ring of Hiroshima Synchrotron Radiation Center. At the minimum gap, achievable lowest photon energies are 3.1 eV, 6.5 eV, and 4.8 eV for horizontal linear, vertical linear, and circular polarization, respectively. Observed photon energies of fundamental and higher harmonic radiations are in good agreement with those of model calculations using measured magnetic field of undulator and the HiSOR beam parameters. Also, observed flux through a slit and a grating monochromator was more than twice larger than that from previously installed 100-mm-period helical undulator for the whole range of radiation spectra. The feedforward COD correction was done to avoid the intensity fluctuation of photon beam in other beamlines due to the gap and phase motion of undulator. No fatal effect on the stored electron beam by installing the undulator was observed though a slight beam size change was observed at the minimum gap.

Electronic and spin structures of solids investigated by means of synchrotron radiation photoemission

Recent progress in research on electronic and spin structures of solids and instrumentation on spin-resolved photoemission at Hiroshima Synchrotron Radiation Center are reported. The fine details of electron dynamics of a typical multiband superconductor Sr2RuO4 were uncovered by high-resolution angle-resolved photoemission spectroscopy (ARPES) with tunable polarizations, and the surface of W(110) was found to have a Dirac-corn-like state of d character with nearly massless energy dispersion by high-resolution ARPES and spin-resolved ARPES (SARPES). The SARPES system with very low energy electron diffraction spin detector and modified VG-SCIENTA R4000 electron analyzer brought a breakthrough in spin detection efficiency as well as energy and angular resolution, and enables precise SARPES measurements for materials that require high energy and angular resolution.

End station for nanoscale magnetic materials study: Combination of scanning tunneling microscopy and soft X-ray magnetic circular dichroism spectroscopy

We have constructed an end station for nanoscale magnetic materials study at the soft X-ray beamline HiSOR BL-14 at Hiroshima Synchrotron Radiation Center. An ultrahigh-vacuum scanning tunneling microscope (STM) was installed for an in situ characterization of nanoscale magnetic materials in combination with soft X-ray magnetic circular dichroism (XMCD) spectroscopy experiment. The STM was connected to the XMCD experimental station via damper bellows to isolate it from environmental vibrations, thus achieving efficient spatial resolution for observing Si(111) surface at atomic resolution. We performed an in situ experiment with STM and XMCD spectroscopy on Co nanoclusters on an Au(111) surface and explored its practical application to investigate magnetic properties for well-characterized nanoscale magnetic materials.

Efficient spin resolved spectroscopy observation machine at Hiroshima Synchrotron Radiation Center

Highly efficient spin- and angle-resolved photoelectron spectrometer named ESPRESSO (Efficient SPin REsolved SpectroScopy Observation) machine has been developed at the beamline BL-9B in Hiroshima Synchrotron Radiation Center. Combination of high-resolution hemispherical electron analyzer and the high-efficient spin detector based on very low energy electron diffraction by the ferromagnetic target makes the high-energy resolution and angular resolution compatible with spin- and angle-resolved photoemission (SARPES) measurement. 7.5 meV in energy and ±0.18° in angular resolution have been achieved with spin resolution. The ESPRESSO machine, combination of quick energy-band dispersion measurement and Fermi surface mapping by two-dimensional electron detector for the spin integrated ARPES and the high-efficient spin analysis by the efficient spin detector realizes the comprehensive investigation of spin electronic structure of materials.

PRESENT STATUS AND FUTURE PLAN OF COMPACT SR RING HiSOR

Hiroshima Synchrotron Radiation Center (HSRC) is a common facility for research and education in the field of synchrotron radiation science in Japan. The major role of the facility is to promote nationwide SR research activities in materials science, especially in solid state physics, and education in the related fields simultaneously. HiSOR is a compact synchrotron radiation source of HSRC constructed in 1996 as a typical VUV — soft X-ray source (0.87 keV critical photon energy) similar to Helios in Singapore. Because of a compact racetrack-type ring, its natural emittance 400π nm · rad is not so small as the other standard-sized rings. There are two undulators, one linear for 26–300 eV range and the other helical/linear for 4–40 eV. The most outstanding feature of the facility lies in the good combination with beamlines to attain high-resolution (below 1 meV) for photoemission spectroscopy. It is routinely operated from 09:00 to 20:00 on weekdays at the stored current starting from 350 mA with 8 h lifetime at 300 mA. HiSOR has been running over 10 years, thus, it is time to think about the future improvements of the facility. The motivation is to pursue the leading position in the field of materials science (solid state physics) using SR for high-resolution photoemission spectroscopy. Some candidates for the upgraded HiSOR are presented.

The self-calibration of a retarding-type Mott spin polarimeter with a large collection angle

We have developed a compact retarding-type Mott spin polarimeter with a large collection angle at the Hiroshima Synchrotron Radiation Center and obtained a reliable value of the effective Sherman function by a self-calibration method. The spin polarization of secondary electrons was evaluated by extrapolation of the left-right scattering asymmetry at the zero energy-loss limit, which enabled us to obtain the effective Sherman function (Seff) and the figure of merit of our polarimeter at different operating conditions.

The performance test of spin-resolved photoelectron spectrometer at HSRC

We have developed a spin-resolved photoelectron spectrometer with a compact retarding-type Mott spin polarimeter at HSRC, Hiroshima Synchrotron Radiation Center, Hiroshima University. Secondary electrons from Ni(1 1 0) were used as the spin-polarized electron source to do performance test of the polarimeter and the best figure of merit was found as 1.8 × 1 0 − 4 for the effective Sherman function and the scattering intensity as − 0.16 and 7.1 × 1 0 − 4 , respectively. Our results show that the self-calibration is possible for this type polarimeter with a large collection angle for scattered electrons.

Structure analyses of biomolecules using a synchrotron radiation circular dichroism spectrophotometer

The vacuum-ultraviolet circular dichroism (VUVCD) spectra of various saccharides and proteins were measured in aqueous solution down to 160 nm, using a VUVCD spectrophotometer at the Hiroshima Synchrotron Radiation Center (HSRC). Most mono- and disaccharides exhibit characteristic peaks at around 170 nm that are sensitive to the anomeric and axial/equatorial configurations of hydroxyl groups, trans– gauche conformations of hydroxymethyl group, and the type of glycosidic linkage. The VUVCD spectra of proteins below 190 nm exhibit characteristic bands corresponding to the different secondary structures. Predicting the content and number of α-helix and β-strand segments is greatly improved, when lower wavelength CD spectra are available. These results demonstrate that synchrotron radiation VUVCD spectroscopy is useful for structure analyses of biomolecules based on the higher energy transitions of chromophores including hydroxyl and acetal groups.

Interface study for liquid–solid state surface by means of the S K‐edge NEXAFS method

AbstractThe adsorption behavior of a sulfur‐containing amino acid molecule on a transition metal surface has been investigated in the bio‐catalytic and surface reaction fields. For a liquid sample there are many difficulties in x‐ray absorption fine structure (XAFS) measurement in the soft x‐ray energy region. In this study we have constructed a new XAFS measurement system with He‐path and Be window at soft x‐ray beamline (BL‐3) at the Hiroshima Synchrotron Radiation Center (HSRC). Copyright © 2004 John Wiley & Sons, Ltd.

High-resolution photoemission spectroscopy of d,f electron systems at the Hiroshima Synchrotron Radiation Center

Recently, high energy-resolution and low-temperature photoemission spectroscopies (Δ E=4.5∼20 meV and T=6∼300 K) have been realized successfully on undulator beamlines installed at the compact light source at the Hiroshima Synchrotron Radiation Center. In the case of Kondo semimetal CeNiSn, the temperature dependence of the spectra provides clear evidence of pseudogap formation below the characteristic temperature between 50 and 60 K. Resonant photoemission spectra of the Kondo semiconductor CeRhAs and the Kondo semimetal CeRhSb revealed unusual Ce 4f-derived electronic states. The spectral features of CeRhAs differ considerably from the predictions of a periodic Anderson model, while the features of CeRhSb are well described by the model. The spectra of Y 1− x Ca x TiO 3 ( x=0.39) exhibits a sharp Fermi edge at low temperature, corresponding to the metal–insulator transition at ∼150 K, where the carrier density in the Ti 3d bands plays an important role.

Hiroshima Synchrotron Radiation Center – An outline and scientific activities

High energy-resolution and low-temperature photoemission spectroscopies (Δ E=4.5–20 meV and T=6–300 K) have been started on undulator beamlines at Hiroshima Synchrotron Radiation Center with a compact light source. Beamlines for high energy-resolution photoemission spectroscopy and their application to direct observation of pseudogap formation in Kondo systems (CeRhAs, CeRhSb, CePtSn and CeNiSn, LaNiSn) are presented.

Vacuum-Ultraviolet Circular Dichroism of Amino Acids as Revealed by Synchrotron Radiation Spectrophotometer

Abstract We succeeded in constructing a vacuum-ultraviolet circular dichroism (VUVCD) spectrophotometer with a small-scale synchrotron radiation source (0.7 GeV) at Hiroshima Synchrotron Radiation Center (HiSOR). This VUVCD system revealed for the first time the CD spectra of amino acids in aqueous media in the 310–140 nm region under high vacuum. These data, which cannot be observed by any types of existing CD spectrophotometers, now open a new field in the structural analysis of biomaterials on a basis of the higher energy transition of chromophores.

Electron spectroscopies of d,f electron systems at Hiroshima Synchrotron Radiation Center

The Hiroshima Synchrotron Radiation Center has started to deliver the light from 1998. A linear and a helical undulator beamline, dedicated mainly for high energy resolution and low-temperature photoemission spectroscopy, have been installed and applied to studies on research subjects related to d,f electron systems; direct observation of the Ce 4f states in CeRhSb single crystal and metal–insulator transition in Y 1− x Ca x TiO 3 single crystals. Photoemission and inverse photoemission spectroscopies using tunable photon and tunable electron beam have also been developed and employed for research on electronic structure of zincblende and hexagonal MnTe.

Design and performance of a soft X-ray double crystal monochromator at HSRC

A new soft X-ray beamline has been constructed at the Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University. This beamline has a unique mechanism of an exchange system for a monochromator crystal. A double crystal monochromator of a Golovchenko-type is equipped with a crystal bank. The beamline delivers photons with energies from 800 to 5000 eV. Users can obtain the effective X-ray absorption fine structure spectra for Si, P, S, Cl, Ar and K K-edge on this beamline.

Performance and future plan of multimode undulator at HiSOR

The multimode undulator that is able to produce polarized radiation of any ellipticity operates successfully in Hiroshima Synchrotron Radiation Center. The comparison between designed and achieved performance was made. Polarization measurements by using visible–UV polarimeter show as high degree of circular polarization as designed. The future plan of undulator operation as an elliptical multipole wiggler is suggested.

Vacuum-Ultraviolet Circular Dichroism Spectrophotometer Using Synchrotron Radiation: Optical System and On-line Performance

Abstract With the aim of measuring the circular dichroism (CD) spectra of biomaterials in aqueous solutions in the vacuum ultraviolet region between 310 and 140 nm, an optical system withstanding high vacuum was incorporated into the beam line 15 of Hiroshima Synchrotron Radiation Center (HiSOR). The performance of the constructed system was confirmed to be satisfactory in the high-vacuum on-line experiments by monitoring the CD spectra of ammonium d-camphor-10-sulfonate, d- and l-alanines in water.

Activities of Hiroshima Synchrotron Radiation Center — photoemission and inverse photoemission of semiconductors

In situ measurements of ultraviolet photoemission and inverse photoemission spectra are successfully applied to studies of the electronic structure of semiconductors. Our experimental results for diluted magnetic semiconductor Cd1−xMnxTe, zincblende MnTe and hexagonal NiAs-type MnTe are presented to discuss the Mn 3d spin-exchange splitting energy and degree of p–d hybridization. An outline of Hiroshima Synchrotron Radiation Center, which has incorporated activity on photoemission and inverse photoemission spectroscopies, is presented, with its brief history, role, light sources and beamlines.