Kouichi Ichikawa

Photoelectron Spectroscopic Study of LiH

The X-ray photoelectron spectrum and the Li K photoelectric yield spectrum of LiH have been measured to study the electronic structure of the valence band and the conduction band. The structure of the spectra is compared with the existing energy-band calculations of LiH. The calculated energy band including the correlation-relaxation effects explains qualitatively the observed shapes of the spectra. However, in detail there exist several discrepancies between the experimental and the calculated results with respect to the band width and the energy differences among the core level, the valence band and the conduction band.

The Soft X-Ray Emission Spectra of the Aluminum-Transition Metal Alloys

The Al L 2,3 emission spectra of Al-Mn, Al-Co, Al-Ni and Al-Cu alloys with various composition of transition metals have been measured with a grazing incidence spectrometer. The results show that the Fermi edges of the Al L 2,3 emission spectra of the alloys do not markedly shift with the change of phase, and that the energy levels arising from the 3d states of the transition metal and contributing to the formation of the conduction band of the alloy locate at a few electron volts below the Fermi edge in any phases of the aluminum-transition metal alloys.

Temperature-Dependent Angle-Resolved Photoemission Spectra of TlInSe2: Manifestations of Incommensurate and Commensurate Phases

The energy band structures of the valence band of the TlInSe2 material with a quasi one-dimensional chain structure and a giant Seebeck coefficient at temperatures below 413 K were investigated by angle-resolved photoemission spectroscopy at 280 and 50 K. The obtained energy bands and the calculated band structure were found to correspond well in main futures. A detailed analysis using both experimental and theoretical data was performed and the obtained results were evident of the presence of the incommensurate phase linked to a certain point on the A line of the Brillouin zone of TlInSe2. A self-consistent picture of the phase transition in TlInSe2 was drawn after discussion using available data for this material. According to this picture, TlInSe2 at 50 K is already a commensurate material while the incommensurate-commensurate phase transition occurs between 280 and 50 K.

Photoemission study of benzene adsorbed on Si surfaces

Abstract Chemisorbed states of C 6 H 6 onSi(111)7 × 7 andSi(100)2 × 1 surfaces are studied by Si2 p core-level photoemission and polarization dependent C K photoabsorption measurements. The Si2 p spectrum of theSi(111)7 × 7 surface shows that charge transfer from the rest atom possibly to the adatom occurs upon C 6 H 6 chemisorption. It is considered that the charge transfer plays an important role in chemisorption of C 6 H 6 on theSi(111)7 × 7 surface. The C K photoabsorption spectra of chemisorbed C 6 H 6 show that the C ring plane is nearly parallel to both surfaces. However, C 6 H 6 on theSi(100)2 × 1 surface is distorted by chemisorption.

Monochromator for circularly polarized synchrotron radiation in the energy range of 5–250 eV

A new spherical grating monochromator with translational and rotational assembly including a normal incidence mount (SGM‐TRAIN) is under construction at BL 5A of the UVSOR Facility, IMS, and its design concept is reported. The following points have been taken into account in the design: (1) Energy range of 5–250 eV, (2) use both of undulator and bending magnet radiation, (3) linear and circular polarizations, (4) spectral purity, (5) resolution, and (6) length of beamline. It should be stressed that the SGM‐TRAIN is useful for experiments where circularly polarized synchrotron radiation is used. Moreover, the SGM‐TRAIN has the advantage that the small emittance of storage ring and the large space for a long beamline are not necessary.

Soft X-Ray Emission and X-Ray Photoelectron Spectra of Titanium Oxides

The spectra of the Ti L 2,3 emission, Ti M 2,3 emission, Ti L 2,3 photoelectron yield, and X-ray photoemission have been measured on titanium oxides, TiO 0.3 , TiO 0.84 , TiO 0.9 , TiO 1.1 and TiO 1.22 , by the use of a grazing incidence spectrometer and an electrostatic electron energy analyzer of hemisphere type. Results are compared with the calculated density of states proposed till now with emphasis on the effect of the oxygen concentration on the electronic structure. It is shown that the major part of the 3 d state in titanium oxides locates at about 5 eV above the Fermi level and has the width of about 4 eV, and this state may extend below the Fermi level.

Photoemission Study of CeO2 and SrCeO3

Photoemission spectra of CeO2 and SrCeO3 have been measured in the Ce 4d → 4f photoabsorption region. The yield spectra of these compounds resemble each other in shape. The valence-band emission of SrCeO3 shows the resonant enhancement in the giant absorption region and the 4f-derived emission exhibits a single-peak distribution such as obtained in CeO2. Moreover, the Ce 3d photoemission spectrum of SrCeO3 has a three-peak structure. These results indicate the strength of the hybridization between the Ce 4f and O 2p states in the ground state of SrCeO3 is similar to that in CeO2.

Resonant x-ray emission spectra of CuO and La2CuO4

The 3d → 2p x-ray emission spectra of CuO and La2CuO4 are measured under the selective excitation from the Cu 2p core-level to the Cu 3d level. The main peak is observed at about 1.5 eV below the absorption peak in both materials. The width of the main peak in CuO is somewhat narrower than that in La2CuO4. In La2CuO4, a satellite is observed at 3.5 eV below the main peak, while the spectrum of CuO does not show a satellite clearly. The main peaks in both materials are ascribed to the transition to the 3d9 excited state and the satellite is attributed to the 3d10v-charge-transfer excited state. From the above results, it is confirmed that the hybridization between the 3d9 and 3d10v states is larger in La2CuO4 than in CuO.

3p - 3d resonant photoemission study of at low temperature

We have studied the Co 3d state of in the temperature range 20 - 110 K by using resonant photoemission spectroscopy in the Co photoabsorption region. By raising the sample temperature from 20 to 110 K, the Co 3d derived emission near the top of the valence band is transferred to higher binding-energies, and the relative peak intensity of two peaks in the satellite is changed. This is interpreted by a spin-state transition of the Co ion.

Rare-Earth N4,5 Absorption Spectra of Some Rare-Earth Compounds

The rare-earth N 4,5 absorption spectra of rare-earth compounds RCl 3 , (R=La, Ce, Sm, Eu and Gd) and RB 6 (R=La and Sm) were measured to obtain the informationon the excited state 4 d 9 4 f n +1 of these substances, where n equals the number of the 4 f electrons in the ground state. The structures of the absorption spectra are well explained by the multiplet states of the 4 d 9 4 f n +1 configuration in the final state. The Sm N 4,5 absorption spectrum of SmB 6 shows no distinct indication due to the Sm 2+ ion regardless of the valence mixing between the Sm 2+ and Sm 3+ ions. The absorption structure corresponding to the Sm 2+ ion may be smeared owing to the autoionization process of the excited state 4 d 9 4 f 7 of the Sm 2+ ion because this state is located above the 4 d ionization threshold of the Sm 2+ ion.