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Inner-shell excitation spectra and fragmentation of nitromethane (NM) clusters have been studied in the oxygen K-edge region under cluster beam conditions. Besides the protonated clusters (NM)n · H+, we identified the production of series of mixed fragment-cluster cations, [(NM)n · X+, (X = CH3, NO, NO2)] in time-of-flight spectra of the NM clusters. "Cluster-specific" excitation spectra could be generated without contribution of free molecules by monitoring partial-ion-yield spectra of the fragments originating from the clusters. Comparison of the "cluster-specific" band with "monomer" band revealed that the first resonance ${\rm O}1s \to \pi^*_{\rm NO}$ band of clusters shifts to a high energy by ~ 0.1 eV. The core-excitation spectrum to the antibonding state compared well with theoretical prediction. The band-shift of the first ${\rm O}1s \to \pi ^*_{\rm NO}$ was interpreted as being due to the weak hydrogen-bond interaction formed upon clustering. Fragmentation mechanism of the core-excited NM cluster...

The adsorption reaction of (CH3)2S on oxygen pre-covered Rh(111) surface has been investigated by XPS and S K-edge NEXAFS techniques. The dissociation of (CH3)2S to methanethiolate and atomic sulfur occurs without regard to the coverage of pre-covered oxygen at 90 K. XPS and NEXAFS results indicate that some of the adsorbates bond to atomic oxygen via their sulfur atom. It seems that adsorbates bonding to atomic oxygen are difficult to desorb from the surface, even if it is heated up to 200 K.

The Pd nanoparticles were fabricated by the gas evaporation method without any capping molecules. It is found that the average diameter of the nanoparticles are 1.7 nm with standard deviation of 0.8 nm by AFM observations. The chemical states of the nanoparticles were measured by the in situ XPS. The XPS results indicate that the chemical states of the nanoparticles become almost the same as the bulk Pd. The chemical states of the air-exposed Pd nanoparticles were also observed by the ex situ XPS and NEXAFS methods. Both ex situ XPS and NEXAFS measurements indicate that the nanoparticles were naturally oxidized under an atmospheric environment. Considering from the behavior of Pd 3d XPS and the diameter of nanoparticles, it is suggested that the depth of oxidized Pd layer is less than 1.4 monolayer from the nanoparticles surface.

We investigated the Raman spectra as a function of the total electric charge consumed in forming porous silicon. It was found that the Raman peak shifted to the lower wave number side as the total electric charge increased. However, the width of the Raman line was insensitive to the total electric charge. It shows the size of nanocrystallites can be widely ranged regardless of the degree of electrochemical reactions during anodization.

The valence-band and conduction-band electronic structure of pyrite-type CoSe 2 has been investigated by means of ultraviolet-photoemission, synchrotron-radiation-photoemission and inverse-photoemission spectroscopies. The fully occupied Co 3d states with t 2g symmetry are observed as a main peak at -1.0 eV relative to the Fermi level (E F ), and the partially filled Co 3d states with e g symmetry are observed as a shoulder at the E F side of the main peak. On the other hand, the structure due to the unoccupied Co e g states appears at 0.6 eV in the inverse-photoemission spectrum. The electronic structure of CoSe 2 is similar to that of CoS 2. The electron correlation is more important for CoSe 2 than for CoS 2.

Valence-band and Yb 4d photoemission spectra of YbXCu 4 (X=In, Cd, Mg) have been measured with high energy resolution from 10 to 300 K. In the valence-band photoemission spectra of YbInCu 4 and YbCdCu 4, the structure due to the Yb 2+ 4f 7/2 states is clearly observed near the Fermi level (E F ) at 10 K. The intensity of the Yb 2+ 4f 7/2 structure decreases with increasing temperature and the structure almost disappears at 300 K. The amount of the enhancement from 50 to 107 K is much stronger for YbInCu 4 than for YbCdCu 4. On the other hand, the Yb 2+ 4f 7/2 structure of YbMgCu 4 is observed as a broad peak near E F and the spectra show little temperature dependence. In the Yb 4d photoemission spectra of YbInCu 4 and YbCdCu 4, the structures due to the Yb 2+ and Yb 3+ states are recognized. The intensity ratio Yb 2+/ Yb 3+ increases with decreasing temperature. In the Yb 4d spectra of YbMgCu 4, on the other hand, almost only structures due to Yb 2+ states are observed.

The valence-band and conduction-band electronic structure of CoSb 3 crystals with a skutterudite type has been investigated by means of ultraviolet photoemission (UPS) with a He discharge lump (hν = 21.2 and 40.8 eV), synchrotron-radiation photoemission (SRPES) and inverse-photoemission spectroscopies (IPES). In the valence bands, the structures at -1.1, -2.5 and -5.8 eV relative to the Fermi level (E F ) are observed in both UPS spectra and SRPES spectra. Taking into account the photoionization cross sections of Co 3d and Sb 5p states and the crystal field splitting of Co 3d states due to the Sb-square ring around Co-ion sites, the main peak at -1.1 eV is attributed mainly to the Co t 2g states, while the Sb 5p states are expected to contribute to the structures at -2.5 and -5.8 eV with a small admixture of Co 3d states. On The other hand, in the conduction bands, a broad feature is observed from E F to ~ 4 eV and a dip is slightly found at around 1 eV. The structures near E F and at around 3.5 eV are considered to be due to the Co e g and hybridization bands between Sb 5p and Co 3d states, respectively.

We already reported the spin- and angle-resolved photoelectron measurements of Ni(110), Ni (110)- p (2 × 1) O and Ni (110)- c (2 × 2) S along the [Formula: see text] line of the Ni(110) surface Brillouin zone using He I radiation. We found that the structure at about 1.3 eV binding energy showed unusual character near the [Formula: see text] point. The spin polarization of this structure was observed to be negative. After the adsorption of oxygen and sulfur on the Ni(110) surface, the degree of negative spin polarization was found to decrease. To study the property of this state, that it is a bulk or surface-related, and to clarify the origin of the negative polarization, we performed spin- and angle-resolved photoemission measurements for Ni(110) along the LW line of its bulk Brillouin zone. The results show that this negative polarization structure can be attributed to a surface state near the [Formula: see text] point.

We report an experimental system dedicated for high-resolution and low-temperature photoemission spectroscopy installed on the helical-undulator beamline of a compact 700 MeV electron-storage ring (HiSOR) at Hiroshima University. A 3 m off-plane Eagle normal-incidence monochromator at the beamline covers the photon-energy range of hν = 4–40 eV. From the photoemission spectra near the Fermi edge of evaporated Au film, the total energy resolution was estimated to be 4.5 and 7.5 meV at hν = 7.1 and 22.6 eV, respectively. We have also performed photoemission measurements of Yb metal, which demonstrated highly bulk-sensitive spectra for the excitation by low energy photon. The high-resolution photoemission spectra of Y 1 - x Ca x TiO 3 with x = 0.41 in the vicinity of the boundary between the metallic and insulating phases exhibited anomalous temperature dependence in comparison with those of normal metals.

Resonant inverse-photoemission spectra of NiAs-type MnTe have been measured with the tunable photon energy mode at kinetic energies of incident electrons (Ek) in the Mn 3p–3d excitation region. The peak structure at 2.9 eV above the valence-band maximum (VBM) is resonantly enhanced at Ek = 50 eV and is attributed to transitions to d 6 final states with 5 E and 5 T 2 symmetries. The broad structure around 12 eV above the VBM in the spectrum at Ek = 46.5 eV and a shoulder on the higher energy side of the main peak at 2.9 eV in the spectrum at Ek = 50 eV is assigned to [Formula: see text] final states and d6 final states with 3Γ symmetries, respectively, where [Formula: see text] stands for a ligand hole and Γ an irreducible representation.

In order to study the electronic states of solids, using high-resolution, low-temperature photoemission spectroscopy (PES) with tunable photon energies, we have constructed a high-resolution undulator beamline operating in the photon-energy range 26–300 eV at the compact 700 MeV electron-storage ring HiSOR located at Hiroshima University. By way of gas-phase experiments, with photon flux larger than 2 × 1010 photons/s, photon-energy resolving powers of E/ΔE > 16000 and 3800 were obtained at hν ~ 48 eV and ~ 244 eV, respectively. High-resolution PES experiments on evaporated Au at 8 K were performed at the beamline with a total energy resolution of ΔE = 12 meV at hν = 48 eV. Among the first experiments from the beamline, a resonant photoemission study of UNiSn is presented. The U 5f derived peak is significantly enhanced at hν = 98 eV.

For a spin-resolved inverse photoemission spectrometer, the most important component is the electron optics system consisting of a 90° deflector and lenses to transfer the spin-polarized electrons from a GaAs photocathode to the sample at high transmission. We adopt a cylindrical deflector when we construct a spin-resolved inverse photoemission spectrometer. A performance test shows that our electronic optics system has achieved 83% transmission, and also that the cylindrical deflector has no shortcoming compared to the spherical type.