Hisashi Hayashi

Optical spectra of liquid water in vacuum uv region by means of inelastic x-ray scattering spectroscopy

Inelastic x-ray scattering (IXS) spectroscopy using hard x-rays is in principle equivalent to optical spectroscopy as long as momentum transfer can be approximated to be zero. Hence IXS spectra of liquid water which corresponds to vacuum uv absorption were measured at small energy transfers with energy resolution of 0.5 eV. The loss function was derived from the spectra and its convergence for the momentum transfer smaller than 0.28 a.u. was confirmed. The reflectance spectrum and the optical oscillator strength have been calculated from the loss function. It is shown that the optical oscillator strength of liquid water differs considerably from that of gaseous water.

Lifetime-broadening removed X-ray absorption near edge structure by resonant inelastic X-ray scattering spectroscopy

A novel method to measure lifetime-broadening removed (LBR) X-ray absorption near edge structure (XANES) spectra is presented. It makes use of monochromatic incident X-rays near resonant condition as well as a high-resolution spectrometer. Fine structures observed in the resonant inelastic X-ray scattering spectra are compared to high-resolution fluorescent excitation XANES spectra for several copper compounds, demonstrating that the present method can be employed to obtain LBR-XANES.

Anisotropy of hexagonal boron nitride core absorption spectra by x-ray Raman spectroscopy

B as well as N core excitation spectra of hexagonal boron nitride (h‐BN) have been studied by means of x‐ray Raman scattering (XRS) spectroscopy. Transitions from 1s core to σ* and π* states are completely distinguished by anisotropy measurements of XRS, thus making an unambiguous assignment to the symmetries of excited states and offering a sound basis to characterize h‐BN with core absorption spectroscopy.

STATIC STRUCTURE FACTOR AND ELECTRON CORRELATION EFFECTS STUDIED BY INELASTIC X-RAY SCATTERING SPECTROSCOPY

Inelastic x-ray scattering spectra of methanol, acetonitrile, benzene, and cyclohexane have been measured with 2 eV resolution for momentum transfer q between 0.69 and 2.77 a.u. using synchrotron radiation from the photon factory (PF) storage ring. By utilizing the Bethe sum rule, the spectra were brought onto an absolute scale, so that the static structure factor S(q) has been obtained. S(q) of these molecules has also been calculated at the single reference configuration interaction (CI) with several types of basis sets. A new formula is proposed to carry out spherical averaging accurately. It is concluded that the CI singles and doubles (CISD) treatment is necessary to predict correct S(q), and that an inclusion of polarization function influences S(q) significantly at this level. An addition of f functions also improves the agreement with the experiments. S(q)’s based on CISD wave functions are in good agreement with the experimental ones, in particular at large q.

Accurate Measurements of Dielectric and Optical Functions of Liquid Water and Liquid Benzene in the VUV Region (1-100 eV) Using Small-Angle Inelastic X-ray Scattering.

Using a third-generation synchrotron source (the BL12XU beamline at SPring-8), inelastic X-ray scattering (IXS) spectra of liquid water and liquid benzene were measured at energy losses of 1-100 eV with 0.24 eV resolution for small momentum transfers (q) of 0.23 and 0.32 au with ±0.06 au uncertainty for q. For both liquids, the IXS profiles at these values of q converged well after we corrected for multiple scattering, and these results confirmed the dipole approximation for q ≤ ∼0.3 au. Several dielectric and optical functions [including the optical oscillator strength distribution (OOS), the optical energy-loss function (OLF), the complex dielectric function, the complex index of refraction, and the reflectance] in the vacuum ultraviolet region were derived and tabulated from these small-angle (small q) IXS spectra. These new data were compared with previously obtained results, and this comparison demonstrated the strong reproducibility and accuracy of IXS spectroscopy. For both water and benzene, there was a notable similarity between the OOSs of the liquids and amorphous solids, and there was no evidence of plasmon excitation in the OLF. The static structure factor [S(q)] for q ≤ ∼0.3 au was also deduced and suggests that molecular models that include electron correlation effects can serve as a good approximation for the liquid S(q) values over the full range of q.

Probe for Spin- and Valence-Selective X-ray Absorption Fine Structure Spectroscopy: EuLγ4 Emission

EuLgamma(4) emission spectra of EuS, EuF(3), EuCl(3), and Eu(2)O(3) were measured using a multicrystal, multidetector spectrometer. Splitting of the EuLgamma(4) band was observed in the EuS spectra and attributed to exchange interactions between Eu5p and Eu4f. It was shown that because of this splitting, the EuLgamma(4) emission could be used for performing spin-selective measurements. This emission exhibited a large chemical shift (approximately 5 eV), depending on the valence state of a compound. The applicability of this emission to valence-selective X-ray absorption fine structure spectroscopy was demonstrated through partial fluorescence yield measurements performed on a 1:1 mixture of EuS and Eu(2)O(3) and on a valence-fluctuating compound Eu(3)Pd(20)Ge(6).

Frictional Properties of Nickel and Copper Implanted Low Carbon Steel Plates

A study has been made of the frictional properties of nickel and copper implanted steel plates. Ion implantation was performed with doses of 1×1015–3×1017 ions/cm2 energies of 50–200 keV. The friction coefficients of Ni and Cu implanted specimens, measured at atmospheric room temperature with a Bowden-Leben type friction testing machine, had a tendency to increase as the total dose increased and the acceleration energy decreased. Concentration profiles were measured by secondary ion mass analysis in order to investigate the element concentration which contributes to the frictional properties. The results suggest that the amount of implanted ions remaining in the surface layer (0–400 A) is of first importance in the frictional properties of Ni and Cu implanted steel plates.

X-Ray Resonant Raman Spectra of Several Copper Compounds

Resonant effect in X-ray Raman spectra of various copper(I) and copper(II) compounds was studied by using tunable X-rays from synchrotron radiation. Prominent excitation energy dependence in spectral shape as well as in intensity was observed and analyzed in terms of simple equations derived from Kramers-Heisenberg equation. Anomaly in spectral shape was observed for Cu(II) compounds and it is ascribed to existence/nonexistence of a vacant 3d orbital in Cu(II)/Cu(I) compounds.

Bethe surfaces and X-ray incoherent scattering factor for H2O studied by electron energy loss spectroscopy

Abstract An angle-resolved electron energy loss apparatus has been constructed for studying electron scattering by gaseous molecules. Generalized oscillator strength distribution of H 2 O has been determined by the use of the Bethe sum rule and is presented as a form of Bethe surface, covering the momentum transfer range from 0.52 to 3.36 a.u. and the energy loss range up to 400 eV. X-ray incoherent scattering factor or static structure factor S ( K ) has been subsequently derived and compared with those by theoretical calculations as well as by inelastic X-ray scattering studies. S ( K )s by the three different methods show remarkable agreement.

NO-induced morphology changes by XAFS study

Abstract XAFS study shows that very small Ru cluster was prepared on γ-alumina, the coordination number being less than 4. In such a small cluster NO adsorption, like CO adsorption, induces a significant structural change of Ru clusters. Metal clusters were, however, not recovered by desorption of NO, unlike CO desorption. The difference in morphology change by CO and NO adsorption is discussed.