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Biomedical subjects

E Shigemasa

Publications and source records attributed to E Shigemasa.

At least 19 recordsLinked to original sources
PubMed2006

Experimental investigation of core-valence double photoionization.

Core-valence double photoionization has been observed in Ne atoms and N2 molecules using a magnetic-bottle time of flight spectrometer. The multielectron coincidence data sets give complete information on the energy correlations between all emitted electrons, which supports a detailed description of the core-valence double photoionization processes including direct spectroscopy of the core-valence doubly ionized states, the final states populated by their Auger decay and details of the dynamics of core-valence double photoionization for selected states.

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PubMed2005

Photofragmentation study of hexamethyldisiloxane following core ionization and direct double ionization.

X-ray photoelectron spectroscopy and Auger spectroscopy studies of gas-phase hexamethyldisiloxane (HMDSO) are presented. The photodissociation of this molecule is studied using various experimental coincidence techniques. We compare the fragmentation pathways observed after core ionization followed by Auger decay and after valence double photoionization of the molecule. A strongly selective production of the doubly charged tetramethyldisiloxane ion is observed in the low binding-energy regions. Theoretical calculations are carried out to tentatively explain the stability of the produced dication.

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PubMed2002

Nondipolar electron angular distributions from fixed-in-space molecules.

The first indication of nondipole effects in the azimuthal dependence of photoelectron angular distributions emitted from fixed-in-space molecules is demonstrated in N (2). Comparison of the results with angular distributions observed for randomly oriented molecules and theoretical derivations for the nondipole correction first order in photon momentum suggests that higher orders will be needed to describe distributions measured in the molecular frame.

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PubMed2001

Dynamical angular correlation in molecular Auger decay.

The first measurements of the angular distribution of Auger electrons from fixed-in-space molecules have been performed in the C K-shell ionization region of CO, for both parallel and perpendicular orientations of the molecular axis with respect to the light polarization vector. The angular distributions obtained for the CO(2+)B(1)Sigma Auger final state show dramatic spectral variations, which also depend on the initial ionization channels, Sigma or Pi, and on the ionization photon energy. This dynamical angular correlation process strongly suggests the breakdown of a two-step model in which the Auger decay is treated independently of the initial photoionization process.

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PubMed2001

Mg and Al K-edge XAFS measurements with a KTP crystal monochromator.

There has been a strong demand for monochromator crystals with a large lattice spacing in order to measure EXAFS spectra at the Mg and Al K-edges. We have introduced a pair of KTP crystal at BL1A of the UVSOR facility and examined its performance in the energy range between 1200 and 2000eV. This crystal monochromator can supply stable photon beams enough to measure the EXAFS spectra for the Mg and Al K-edges. Advantages of the KTP crystal are discussed in comparison with a YB66 crystal monochromator.

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PubMed1998

Submicrometre-area high-energy-resolution photoelectron spectroscopy system.

A submicrometre-area photoelectron spectroscopy system that uses a multi-layer-coated Schwarzschild objective as the soft X-ray microbeam optics has been developed. The system is located at an undulator beamline (BL-16U) at the Photon Factory in the High Energy Accelerator Research Organization. By knife-edge measurement, the microbeam size was estimated to be 160 nm at the sample position using a 25-75% criterion. Photoelectron spectral measurements revealed that the Fermi edge width was 0.12 eV, which means that the instrumental resolution was 0.05 eV, after removing the natural broadening of the Fermi edge at room temperature. This system offers both high energy resolution and high spatial resolution.

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PubMed1998

High-resolution spherical grating monochromator for the undulator beamline (BL-16B) at the Photon Factory.

The design and performance of a 24 m high-resolution spherical grating monochromator (H-SGM) for the undulator beamline (BL-16B) at the Photon Factory are described. With three interchangeable gratings of 400, 900 and 2000 lines mm(-1), the H-SGM is designed to cover the photon energy range 40-600 eV. With a resolving power of approximately 2000 in the photon energy range 40-530 eV, more than 10(11) photons s(-1) have been measured. The best resolutions obtained so far, at a substantially lower photon flux, are greater than 10 000 at 250 eV and 8000 at 400 eV

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