二木 かおり

Photocatalytic reduction of CO2 into C2,3 hydrocarbons completes a C‐neutral cycle. The reaction pathways of photocatalytic generation of C2,3 paraffin and C2H4 from CO2 are mostly unclear. Herein, a Co0–ZrO2 photocatalyst converted CO2 into C1–3 paraffin, while selectively converting CO into C2H4 and C3H6 (6.0 ± 0.6 μmol h−1 gcat−1, 70 mol%) only under UV–visible light. The photocatalytic cycle was conducted under 13CO and H2, with subsequent evacuation and flushing with CO. This iterative process led to an increase in the population of C2H4 and C3H6 increased up to 61–87 mol%, attributed to the accumulation of CH2 species at the interface between Co0 nanoparticles and the ZrO2 surface. CO2 adsorbed onto the O vacancies of the ZrO2 surface, with resulting COH species undergoing hydrogenation on the Co0 surface to yield C1–3 paraffin using either H2 or H2O (g, l) as the reductant. In contrast, CO adsorbed on the Co0 surface, converted to HCOH species, and then split into CH and OH species at the Co and O vacancy sites on ZrO2, respectively. This comprehensive study elucidates intricate photocatalytic pathways governing the transformation of CO2 into paraffin and CO to olefins.

Using layered double hydroxide as a precursor, the negative electrode characteristics of Al³⁺ ion dissolved NiO were investigated. Al³⁺ ion shows reversible redox activity to Al when introduced into a host having electron conductivity and a lithium ion diffusion path.

Abstract To understand the relationship between the shape of X-ray magnetic circular dichroism (XMCD) and magnetic moments, we calculate V L2, 3-edge XMCD spectra for Mn₂VAl while varying the magnetic moment of an absorbing atom V. We find that XMCD spectra change depending on the magnetic moment of the absorbing atom. We explain these changes based on the magnetic moment dependence of atomic terms, which are components of XMCD. When the overlaps between radial functions and photoelectron wave functions are considered, an atomic term has a value at its energy. The peak positions of the radial integral for up and down spin are different, which leads to multiple peaks of the atomic terms and determines the positive and negative direction of the peak.

Keldysh Green’s function approach is used in order to derive a practical formula to study pump-probe ultrafast photoemission spectra. The pump pulse is strong whereas the probe pulse can be treated by use of a perturbation theory: We expand the full Green’s function in terms of electron-probe pulse interaction and renormalized Green’s function including pump pulse excitation. Random Phase Approximation (RPA)-boson approach is introduced to estimate some important factors. Well above the edge, ultrafast photoelectron diffraction provides us with information on the transient structural change after the pump pulse excitation. In addition to these slow processes, the rapid oscillation plays an important role related to electronic excitation by pump pulse.

A short review is presented on theoretical approach to plasmon losses in core-level photoemission from simple metals. Full multiple elastic scatterings of photoelectrons are taken into account before and after the plasmon losses within the quantum cumulant (Landau) formula that can describe both intrinsic and extrinsic losses, and overall features of core level photoemission. Far from normal emission and in low energy excitation, we cannot apply these simple exponential formulas.

Angle resolved photoemission spectroscopy (ARPES) gives detailed information about the surface electronic structures and oriented molecules. In the so-called orbital tomography method, the ARPES intensity is obtained by a simple Fourier transform of the initial state molecular orbital. While this method has given good results for a number of pi-orbital systems, it is known to have strong limitations because the final state is approximated as a plane wave and thus photoelectron scattering is completely neglected. Here we propose an ARPES theory where the initial states are taken from a quantum chemistry method and the final states are calculated in multiple scattering theory. The initial Molecular orbitals are reexpanded in a multi-site spherical wave basis and the multiple scattering potential is constructed from the ab initio charge density. These computations are performed algebraically using newly developed algorithms. The method is applied to pentance and the results are compared with the plane wave approximation. (C) 2017 Published by Elsevier B.V.

We have successfully determined the internuclear distance of I-2 molecules in an alignment laser field by applying our molecular structure determination methodology to an I 2p X-ray photoelectron diffraction profile observed with femtosecond X-ray free electron laser pulses. Using this methodology, we have found that the internuclear distance of the sample I-2 molecules in an alignment Nd: YAG laser field of 6 x 10(11) W/cm(2) is elongated by from 0.18 to 0.30 angstrom "in average" relatively to the equilibrium internuclear distance of 2.666 angstrom. Thus, the present experiment constitutes a critical step towards the goal of femtosecond imaging of chemical reactions and opens a new direction for the study of ultrafast chemical reaction in the gas phase.

We have theoretically studied the azimuthal angular dependance of surface and bulk plasmon losses in Al 2s photoemission spectra. Here, full multiple scatterings of photoelectrons are taken into account before and after plasmon losses within the quantum Landau formula, which can describe overall features of the photoemission bands. By considering elastic scattering, the azimuthal angular dependence can be evaluated. Two types of peaks are observed strong peaks attributed to forward focusing and weak peaks appeared as diffraction pattern. Forward focusing peaks are observed when atoms exists in the forward direction. The peak intensities from deeper layers are reduced by the defocusing effect. The origin of the weak peaks are discussed with the local geometric analysis. The differences of main, 1st bulk and surface plasmon loss are discussed. The peaks of diffraction pattern largely changed by increasing the photoelectron kinetic energy.

Keldysh Green's function approach is extensively used in order to derive practical formulas to analyze pump-probe ultrafast photoemission and X-ray absorption spectra. Here the pump pulse is strong enough whereas the probe X-ray pulse can be treated by use of a perturbation theory. We expand full Green's function in terms of renormalized Green's function without the interaction between electrons and probe pulse. The present theoretical formulas allow us to handle the intrinsic and extrinsic losses, and furthermore resonant effects in X-ray Absorption Fine Structures (XAFS). To understand the radiation field screening in XPS spectra, we have to use more sophisticated theoretical approach. In the ultrafast XPS and XAFS analyses the intrinsic and extrinsic loss effects can interfere as well. In the XAFS studies careful analyses are necessary to handle extrinsic losses in terms of damped photoelectron propagation. The nonequilibrium dynamics after the pump pulse irradiation is well described by use of the time-dependent Dyson orbitals. Well above the edge threshold, ultrafast photoelectron diffraction and extended X-ray absorption fine structure (EXAFS) provide us with transient structural change after the laser pump excitations. In addition to these slow processes, the rapid oscillation in time plays an important role related to pump electronic excitations. Near threshold detailed information could be obtained for the combined electronic and structural dynamics. In particular high-energy photoemission and EXAFS are not so influenced by the details of excited states by pump pulse. Random-Phase Approximation (RPA)-boson approach is introduced to derive some practical formulas for time-dependent intrinsic amplitudes. (C) 2015 Elsevier B.V. All rights reserved.

The effects of the spin-orbit interaction on surrounding atoms for XMCD spectra are studied by a real-space multiple-scattering theory. The present numerical calculation for Fe K-edge XMCD spectra from BCC iron demonstrates the importance of the spin-orbit interaction on scattering atoms, which has been disregarded in previous works. These effects will be inevitable for K-edge XMCD analyses of light elements surrounded by heavy magnetic atoms.

To study relationship between friction and plastic deformation modes of single crystals, wear patterns were analyzed for BaSO4, an orthorhombic crystal having various cleavage faces and slip systems. Upon scanning a sapphire stylus along the b-axis at (0 0 1) face, formation of triangular deformation patterns extending outside the wear track were observed with optical microscopy. Atomic force microscopic analysis revealed that the triangular areas were elevated, and the two sides were formed by {2 1 0} cleavage steps, starting within the track, and continued by {1 1 0} slip steps outside the track. Upon scanning with heavier normal loads, lots of {0 1 1} slip steps were formed inside the triangles, presumably due to horizontal compression given by the stylus to the triangular areas isolated from the rest of the surface. Mechanism of the wear pattern formation was proposed. When the stylus was scanned along the a-axis, the wear tracks were segmented into short strips by {1 0 1} slips. Under heavier normal loads, the segment structures were partly destroyed by the stylus, presumably by (0 0 1) slip and cleavage, producing debris on both sides of the track. The changes in deformation patterns under heavier normal loads caused steeper increase in friction curves measured in the two directions. Different deformation modes were activated depending upon the scan directions, normal loads and locations relative to the stylus.

In this short review we discuss recent progress in photoemission theory for organic molecules and their crystals. We discuss some important features in Keldysh Green's function theory for the photoemission. We briefly discuss many-body aspects in photoemission from core and extended levels. In particular phonon effects are investigated in more detail since organic solids are typically soft where electron-phonon interaction is important. Debye-Waller factor suppresses the interference effects of photoelectron waves which makes ARPES analyses useless, particularly in high energy region. (C) 2015 Elsevier B.V. All rights reserved.

Some important phonon effects observed in X-ray absorption and X-ray photoemission spectra are discussed on the basis of nonequilibrium Green's function theory. This theoretical framework allows us to incorporate phonon effects, such as Debye-Waller (DW) factors, Franck-Condon (FC) factors and electron-phonon interactions in a natural way. In the case of core level excitations, we can take into account the core-hole effects in lesser Green's function g(<) and photoelectron propagation in greater Green's function g(>). For the core-hole propagation we derive some formulas to describe the thermally displaced core functions: we have p components even for deep cores orbital due to the thermal motion. We should notice that the thermal fluctuation is quite small but it is already in the order of the spread of the core functions. Applying Mermin's theorem, we can calculate the thermal average of the hole propagator g< : here an important ingredient is the Debye-Waller factor used in X-ray and neutron diffraction. For the pre-edge structures, the intensity associated with forbidden electric dipole transition is sensitive to the temperature compared with allowed electric quadrupole transition. We also discuss the FC and their interference, which have negligible contribution to pre-edge intensity and energy shift. The quasiparticle energy is also influenced by the core displacement which can be responsible for the peak shift of the pre-edges. We also discuss the changes of the photoelectron angular distributions caused by the thermal atomic vibration. (C) 2014 Elsevier B.V. All rights reserved.

We have studied the surface and bulk plasmon losses associated with Li 1s photoemission. Here, full multiple scatterings of photoelectrons are taken into account before and after the plasmon losses within the quantum Landau formula that can describe overall features of the photoemission bands. We compared the depth profiles of the Li 1s single-loss spectra with full multiple scatterings and without elastic scatterings. They are strongly influenced by the elastic scatterings. The model accounting for the full multiple scatterings gives a rapidly decaying function of the depth because of the defocusing effects. Copyright (C) 2014 John Wiley & Sons, Ltd.

Nickel oxide is a p-type semiconductor with wide band gaps of 3-4 eV. The defects of O or Ni atoms are essential to explain some specific features of the semiconductors. The information of the local structure around Ni is important to clarify the conduction mechanism. We investigate the Ni K-edge X-ray absorption fine structure spectra of the nickel oxide thin films in order to obtain the structural information around Ni. For the X-ray absorption near edge structure (XANES) analyses, we apply a full multiple scattering theory. The experimental results suggest that the crystallinity of the thin films depends on the annealing temperature. The distances of Ni-O and Ni-Ni are 1.984 and 2.747 angstrom the sample 100 degrees C and 2.084 and 2.947 angstrom for the sample annealed at 300 degrees C, respectively. Our multiple scattering calculations can satisfactorily explain the experimental result. Copyright (C) 2014 John Wiley & Sons, Ltd.

We study the angular and energy dependence of surface and bulk plasmon losses accompanying deep core excitations in simple metals. Here full multiple scatterings of photoelectrons are taken into account before and after the plasmon losses within the quantum Landau formula, which can describe overall features of the photoemission bands. For example, multiple plasmon loss features can be calculated by use of the formula. Two simple metals, Al and Na, are studied here. The depth profiles of the plasmon losses are strongly influenced by the elastic scatterings. The model assuming single elastic scatterings overestimates the losses from deep emitters due to the forward focusing effects, whereas the model accounting for full multiple scatterings gives a much rapidly decaying function of the depth due to the defocusing effects and rich structures due to the photoelectron diffraction. The single elastic scattering approximation gives a poor result both for the depth profiles and for the loss spectra. The present multiple scattering calculations successfully explain the azimuthal dependence of the loss spectra, which reflect the local geometry around the emitters.

NaCl, MgO, PbS結晶の(001)表面での摩擦について塑性変形と摩擦力の関連を調べた。引掻針を[100], [110]の2方向に垂直荷重を変えて掻引し、摩擦力の測定と摩耗痕の観察を行った。摩擦の増大が起きるとき、硬いMgOでは軸に対し45°方向で針跡の外に達する滑り痕が生じたが、軟らかいNaClでは傷は針跡の内部に留まり、PbSでは割れが生じた。摩擦の異方性は硬くて摩擦係数の小さいMgOでのみ明瞭に観察された。

フタロシアニン(Pc)分子は中心に遷移金属イオンを含み、Fe(Pc)(CN)₂分子ではPc分子と鉄イオン由来の伝導電子と局在モーメント間の分子間相互作用を期待できる。TPP[Fe(Pc)(CN)₂]₂では巨大磁気抵抗が低温で観測された。この起源を解明するため、Fe(Pc)(CN)₂分子の電子状態をX線吸収スペクトルを用い研究した。10Tの強磁場中で鉄のK吸収端を測定し多重散乱理論によって解析した。

Frictional force was measured on directional calcite (1 0 -1 4) surface, where triangular carbonate ions are all tilted to [4 2 -1] direction. With the normal load < 49 mN, observed frictional asymmetry, +[4 2 -1] > -[4 2 -1], was the same as that measured in nm-scale. In the higher normal load range, a new component was added to the friction in -[4 2 -1] direction, and the asymmetry was reversed. Only in the direction of stronger friction, characteristic triangular deformation patterns were formed. Microscopic observation after indentation experiments revealed that the patterns were formed by slip on c (0 0 0 1) faces on one side of the stylus, followed by cleavage on r{1 0 -1 4} faces. A mechanical model was proposed to explain why the deformation occurs only in one quadrant of the surface. The result of scratch perpendicularly in [0 1 0] direction, also supports the mechanism of deformation. The results show when and how the contribution of plastic deformation is added to intrinsic surface friction and affects the frictional asymmetry. The frictional force in the -[4 2 -1] scratch increased linearly with the total lengths of the traces of c-slip.

Indentation experiments and friction measurements were performed at three low index faces of fluorite (CaF₂) crystal. Deformation patterns were analyzed by observing step structures with atomic force microscopy (AFM). Upon indentation at (0 0 1) surface, {1 0 0}<0 1 1> slip steps were formed at limited parts of the surface near the compressed area, where horizontal shear stress is added to vertical one. Upon indentation at (1 1 1) surface, the surface was split into 6 sectors separated by {1 1 1} cleavage lines. Steps formed on each sector were also explained by the {1 0 0}<0 1 1> slip. The signs of steps suggest that the steps in three alternate sectors were formed by vertical compression, and the steps in the other sectors were formed mainly by horizontal compression. The slip mechanism was explained by a simple mechanical model. Upon scratching the (0 0 1) surface in [1 0 0] direction, only steps in [1 0 0] direction, not in [0 1 0] direction, were formed outside the wear track. Scratch on (1 1 1) surface activated the slip in three possible directions selectively, depending upon the scan directions of the stylus. Slip did not occur easily at (1 1 0) surface, where slip can occur in five directions close to each other. Frictional anisotropy was discussed in relation to the slip system.

湿潤空気からPMMA/ベンゼン溶液表面上に凝縮する微小水滴をテンプレートとするハニカムフィルムの形成過程を光学顕微鏡で観察した．ガラス基板上にキャスト後，溶液表面にはベナールセルが形成され，セル境界に水滴が凝縮した．水滴はセルの境界部を通って液滴中心部に集合し，孔径の大きなハニカムを形成した．液滴外周部でも外側へ向かう対流が観測され，小さなハニカム構造が形成された．中心部と外周部の中間の領域では水滴が密に配列せず，規則的なハニカムができなかった．外気温が低いほど目の細かいハニカムができる．壁をつけたガラス基板を使って端の効果を抑制すると全体的に均一なハニカムが形成され，液厚に依存して中心部では規則的なハニカムが整列した．また，基板を0°Cに冷却すると終始外周部へ向かう対流が観察され，中心部から中間部にかけて規則的なハニカムが形成された．

Micro-facet formation processes were observed, with atomic force microscopy (AFM), at various crystal faces of two aragonite-type minerals, cerussite (PbCO3) and strontianite (SrCO3), in dilute aqueous acetic acid. Among the prismatic faces, parallel to the c-axis, electrically neutral (1 0 0) and (1 3 0) faces were stabilized in the acidic environment, as in the case of aragonite (CaCO3). On the other hand, polar (1 1 0) and (0 1 0) faces of PbCO3 remained to be stable, in contrast with the case of aragonite. Even atom-resolved AFM images were observed with the (1 1 0) face, corresponding to the arrangement of carbonate ions, most probably protonated. Since Pb2+ is a more polarizable soft acid. Pb-O bonds bear covalent nature in addition to Coulombic nature. Due to diminished polarity with the bonds, the (1 1 0) face remained stable even in the acidic condition. Among the crystal faces intersecting with the c-axis, stabilization, in the acidic condition, of (1 1 1) faces of SrCO3 and (0 2 1) faces of PbCO3 was observed in contrast to the stabilization of (1 1 2) faces of aragonite, suggesting flexible nature of the mineral faces having larger cations. Relationship between natural crystal forms and growth environment was discussed. (C) 2011 Elsevier B.V. All rights reserved.

Frictional force was measured using Bowden-Leben apparatus with a sapphire stylus at directional (1 0 -1 4) surface of magnesite crystal. Deformation patterns formed during the scratch in ± [4 2 -1] directions were observed with optical microscopy. With the normal load up to 460 mN, no trace of slip or cleavage was observed and the friction coefficient remained at 0.0085. Frictional asymmetry due to the tilt of carbonate ions was not recognized in this range. At higher normal loads, new components were added to the frictional force, with the appearance of traces of slip, and then, cleavage on {1 0 -1 4} faces. In contrast with the case of calcite, traces of the slip remained within the width of the stylus. Traces of the cleavage, on the other hand, reached far outside the wear track, and asymmetry was recognized in the pattern formation. In indentation experiments, the cleavage occurred in four directions, but slip on (0 0 0 1) was not recognized. In contrast with isostructural but softer calcite crystal, the difficulty in the (0 0 0 1) slip with magnesite keep the friction coefficient low toward higher normal loads.

Ortho-para (o-p) conversion of H-2 and para-ortho (p-o) conversion of D-2 were investigated on a Ag surface coadsorbed with O-2 by resonance-enhanced multiphoton ionization combined with photostimulated desorption. Compared with a bare Ag surface, both H-2 o-p conversion and D-2 p-o conversion were accelerated on O-2-covered surfaces, and the conversion time was found to decrease with increasing O-2 coverage. In order to analyze the conversion kinetics, Monte Carlo simulations taking account of hydrogen diffusion on the surfaces were performed and compared with the experimental data. The conversion time of H-2 and D-2 in the vicinity of adsorbed O-2 was estimated to be 8.3 and 53.4 s, respectively. The isotope dependence of the conversion is discussed.

Ortho-para conversion of H(2) and para-ortho conversion of D(2) on an Ag surface were investigated by resonance-enhanced multiphoton ionization combined with photostimulated desorption. The conversion processes were found to be accelerated by laser irradiation at 193 rim, while photo-irradiation at 532 nm had little effect on the conversion time. The natural conversion time Of H2 and D2 was estimated to be 610 and 1030 s, respectively. The roles of electron transfer and rotational-energy dissipation in the conversion are discussed.

We report findings of our investigation on the non-thermal photodesorption dynamics of H(2)(D(2)) initially physi-sorbed on Ag. We photodesorbed the H(2)(D(2)) using a 6.4 eV pump photon, and then state-selectively probed the desorbing H(2)(D(2)) using the resonance-enhanced multi-photon ionization technique. The corresponding time-of-flight (TOF) spectra measured for the initial rotational states J = 1 and J = 0 indicate no particular J dependence. The mean translational temperature was similar to 8 K for both H(2) and D(2.) Using a coherent DIET (desorption induced by electronic transitions) model, we were able to reproduce the TOF spectra, including the observed isotope dependence. (c) 2005 Elsevier B.V. All rights reserved.