The University of Tokyo · Engineering
Professor Yoshihisa Harada's research lab specializes in advanced spectroscopic techniques, particularly high-resolution soft X-ray spectroscopy, to investigate electronic structures and dynamic processes in quantum materials, molecules, and surfaces. The lab focuses on resonant inelastic X-ray scattering (RIXS), X-ray absorption and emission spectroscopy, and electron spectroscopy methods such as PIES and UPS to probe electronic states, charge transfer excitations, and molecular orbital distributions with element- and orbital-specific sensitivity. Their work spans from fundamental studies of electron correlation and magnetic excitations in transition metal oxides to the electronic and vibrational characterization of water and organic semiconductor films, often combining experimental precision with theoretical interpretation to reveal subtle electronic and structural phenomena at the atomic scale.
Figures are computed from collected data and may differ slightly.
An extremely high resolution flat field type slit less soft x-ray emission spectrometer has been designed and constructed for the long undulator beamline BL07LSU in SPring-8. By optimizing the ruling parameters of two cylindrical gratings, a high energy resolution ΔE < 100 meV and/or an E∕ΔE ~ 10 000 are expected for the energy range of 350 eV - 750 eV taking into account the broadening by the spatial resolution (25 μm) of a CCD detector. A coma-free operation mode proposed by Strocov et al., is
High-resolution O 1s resonant inelastic x-ray scattering spectra of liquid H2O, D2O, and HDO, obtained by excitation near the preedge resonance show, in the elastic line region, well-separated multiple vibrational structures corresponding to the internal OH stretch vibration in the ground state of water. The energy of the first-order vibrational excitation is strongly blueshifted with respect to the main band in the infrared or Raman spectra of water, indicating that water molecules with a highl
By means of Penning-ionization electron spectroscopy the outermost surface layer of a pentacene film on a graphite substrate (cleavage plane) was selectively observed. Ultraviolet photoelectron spectroscopy was also applied to observe several layers from the surface. From the analyses of the two types of spectra the subtle changes in the electronic state and the molecular orientation of the outermost layer and also those of inner layers were probed separately during the layer-by-layer epitaxial
Polarization dependence of soft-x-ray Raman scattering was investigated at the Ti $2p$ absorption edge of ${\mathrm{TiO}}_{2}.$ Strong Raman scattering feature appears about 14 eV below elastic peaks with strong polarization dependence. These Raman scattering structures are charge transfer excitations to the antibonding state between ${3d}^{1}{L}^{\ensuremath{-}1}$ and ${3d}^{0}$ states, because they are enhanced when the incident photon energies are tuned at satellite structures of Ti $2p$ abso
The He* Penning ionization electron spectra (PIES) and He I UV photoelectron spectra (UPS) of CO and Fe(CO)5 were measured. The relative intensity of the bands in PIES was shown to give information on the spatial electron distribution of individual molecular orbitals. On the basis of the information together with the results of the population analysis, most of the bands in the UPS of Fe(CO)5 were assigned. The usefulness of PIES in the study of stereochemistry was indicated.
Zhang-Rice singlet excitation around 2 eV is observed, distinguished from Cu $\mathrm{dd}$ excitations, by a symmetry selective resonant soft x-ray Raman scattering (RSXRS) experiments at the O $1s$ edge excitation of ${\mathrm{Sr}}_{2}{\mathrm{CuO}}_{2}{\mathrm{Cl}}_{2}.$ Well below N\'eel temperature the initial state of ${\mathrm{Sr}}_{2}{\mathrm{CuO}}_{2}{\mathrm{Cl}}_{2}$ is antiferromagnetic, and then the final state with the Zhang-Rice singlet is excited selectively when the photon polari
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