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Journal Articles

PANDORA Project for the study of photonuclear reactions below $$A=60$$

Tamii, Atsushi*; Pellegri, L.*; S$"o$derstr$"o$m, P.-A.*; Allard, D.*; Goriely, S.*; Inakura, Tsunenori*; Khan, E.*; Kido, Eiji*; Kimura, Masaaki*; Litvinova, E.*; et al.

European Physical Journal A, 59(9), p.208_1 - 208_21, 2023/09

no abstracts in English

Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

 Times Cited Count:30 Percentile:96.87(Astronomy & Astrophysics)

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:233 Percentile:99.74(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

Development of cesium-free mineralization for decontamination and reuse of radioactive contaminated soil in Fukushima

Shimoyama, Iwao; Honda, Mitsunori; Kogure, Toshihiro*; Baba, Yuji; Hirao, Norie*; Okamoto, Yoshihiro; Yaita, Tsuyoshi; Suzuki, Shinichi

Photon Factory News, 35(1), p.17 - 22, 2017/05

We introduce Cs-free mineralization (CFM) for Cs removal and reuse of radioactive-contaminated soil in Fukushima and report recent work conducted in the BL27A beamline in Photon Factory. In this work, we investigated compositional and structural changes of Cs-sorbed weathered biotite (WB) before and after heating treatment with addition of NaCl-CaCl$$_{2}$$ salts under low-pressure condition, to study Cs desorption mechanism from clay minerals. X-ray fluorescence spectroscopy clarified that almost all Cs and K were removed with the salts at 700 $$^{circ}$$C. On the other hand, Ca increased with heating temperature. X-ray diffraction and transmission electron microscopy analysis clarified that phase transitions from WB to some Ca-rich silicate minerals, e.g., augite, were caused by the heating treatment with the salt. Based on these results, CFM is proposed for Cs removal utilizing the mechanism in which large monovalent cations are discharged with accompanying the phase transition. We also discuss the role of Cl in this reaction showing chemical bonding change of Cl observed using X-ray absorption spectroscopy in the early stage of the chemical reaction.

Journal Articles

Observation of oriented organic semiconductor using Photo-Electron Emission Microscope (PEEM) with polarized synchrotron

Sekiguchi, Tetsuhiro; Baba, Yuji; Hirao, Norie; Honda, Mitsunori; Izumi, Toshinori; Ikeura, Hiromi*

Molecular Crystals and Liquid Crystals, 622(1), p.44 - 49, 2015/12

BB2014-1632.pdf:0.71MB

 Times Cited Count:0 Percentile:0.01(Chemistry, Multidisciplinary)

The molecular orientation is one of the important factors for controlling various properties in organic semiconductor materials. Films are usually heterogeneous. Thus they exist as a mixture of microscopic domains which have a variety of orientation directions. Therefore, it is essential to observe selectively microscopic domains with different orientation direction. In this work, we have developed the photoelectron emission microscopy (PEEM) system combined with the linearly polarized vacuum ultraviolet (VUV) light or synchrotron radiation (SR) X-rays. PEEM images (FOV = ca.50 micro m) for poly(3-hexylthiophene), P3HT thin films were observed under the UV irradiation with various polarization angles, including in-plain and out-of-plain polarization. Morphologies at some bright parts are different each other. The resultant observation suggests that it enables us to distinguish oriented micro-domains with specific directions of polymer chain axis from other amorphous parts.

Journal Articles

Electrochemical immobilization of biomolecules on gold surface modified with monolayered L-cysteine

Honda, Mitsunori; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie

Thin Solid Films, 556, p.307 - 310, 2014/04

 Times Cited Count:5 Percentile:24.07(Materials Science, Multidisciplinary)

Journal Articles

Orientation effect of organic semiconducting polymer revealed using Photo-Electron Emission Microscope (PEEM)

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Hirao, Norie; Honda, Mitsunori; Izumi, Toshinori; Ikeura, Hiromi*

Photon Factory Activity Report 2013, Part B, P. 546, 2014/00

The molecular orientation is one of the important factors for controlling various properties in organic semiconductor materials. Films are usually heterogeneous. Thus they exist as a mixture of microscopic domains which have a variety of orientation directions. Therefore, it is essential to observe selectively microscopic domains with different orientation direction. In this work, we have developed the photoelectron emission microscope (PEEM) system combined with the linearly polarized vacuum ultraviolet (VUV) light or synchrotron radiation (SR) X-rays. PEEM images for poly(3-hexylthiophene), P3HT thin films were observed under synchrotron X-ray irradiation with linearly polarization. In conclusion, it was found that PEEM with polarized synchrotron can be a powerful tool that gives information of molecular orientation in nano-meter scale.

Journal Articles

Orientation of silicon phthalocyanine thin films revealed using polarized X-ray absorption spectroscopy

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Hirao, Norie; Honda, Mitsunori; Deng, J.*

Photon Factory Activity Report 2012, Part B, P. 68, 2013/00

The orientation of organic semiconducting molecules on surfaces plays a crucial role in improving the properties of electronic devices. We prepared thin films of silicon phthalocyanine dichroride (SiPcCl$$_{2}$$) on graphite spin-cast followed by heating to 350$$^{circ}$$C at ambient condition. We investigate the molecular orientation of the films using angle-dependent near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy. Si 1s NEXAFS spectra for the thin films after annealing are very different each other, indicating that the corresponding reactions thus the structures of final products are different. The structures of the reaction products are estimated with the help of ab initio molecular orbital calculations that fit the observed NEXAFS spectra.

Journal Articles

Microscopic observation of lateral diffusion at Si-SiO$$_{2}$$ interface by photoelectron emission microscopy using synchrotron radiation

Hirao, Norie; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori*

Applied Surface Science, 258(3), p.987 - 990, 2011/11

 Times Cited Count:3 Percentile:16.31(Chemistry, Physical)

The lateral surface diffusion at Si-SiO$$_{2}$$ interface has been observed at nanometer scale using photoelectron emission microscopy (PEEM) combined with synchrotron soft X-ray excitation. The samples investigated were Si-SiO$$_{x}$$ micro-patterns prepared by O$$_{2}$$$$^{+}$$ ion implantation in Si(0 0 1) wafer using a mask. The lateral spacial resolution of the PEEM system was about 41 nm. The brightness of each spot in the PEEM images changed depending on the photon energy around the Si ${it K}$-edge, in proportion to the X-ray absorption intensity of the corresponding valence states. It was found that the lateral diffusion occurs at lower temperature than that reported for the longitudinal diffusion at the Si-SiO$$_{2}$$ interface. It was also found that no intermediate valence states such as SiO (Si$$^{2+}$$) exist at the Si-SiO$$_{2}$$ interface during the diffusion. The observed differences between lateral and longitudinal diffusion are interpreted by the sublimated property of silicon monoxide (SiO).

Journal Articles

Chemical-state-selective mapping at nanometer scale using synchrotron radiation and photoelectron emission microscopy

Hirao, Norie; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori

Analytical Sciences, 26(8), p.835 - 840, 2010/08

 Times Cited Count:2 Percentile:7.12(Chemistry, Analytical)

For surface analyses of semiconductor devices and various functional materials, it has become indispensable to analyze valence states at nanometer scale due to the rapid developments of nanotechnology. Since a method for microscopic mapping dependent on the chemical bond states has not been established so far, we have developed a photoelectron emission microscopy (PEEM) system combined with synchrotron soft X-ray excitation. The samples investigated were Si/SiO$$_{x}$$ micro-patterns prepared by O$$_{2}$$$$^{+}$$ ion implantation in Si(001) wafer using a mask. PEEM images excited by various photon energies around the Si ${it K}$-edge were observed. The lateral spacial resolution of the system was about 41nm. The brightness of each spot in PEEM images changed depending on the photon energy, due to the X-ray absorption intensity of the respective chemical state. Since the surface of this sample was topographically flat, it has been demonstrated that the present method can be applied to observations of the microscopic pattern, depending not on the morphology, but only on the valence states of silicon. We have also ${it in-situ}$ measured the changes of the PEEM images upon annealing, and elucidated the mechanism of the lateral diffusion of oxygen and valence states of silicon at the nanometer scale.

Journal Articles

Orientation of Si phthalocyanine investigated by X-ray absorption spectroscopy and molecular orbital calculation

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Honda, Mitsunori; Hirao, Norie; Narita, Ayumi; Deng, J.*

Surface and Interface Analysis, 42(6-7), p.863 - 868, 2010/06

 Times Cited Count:1 Percentile:1.76(Chemistry, Physical)

Metal phthalocyanines (Pc) have attracted growing attention due to potential application as organic semiconductors or light emitters. Recently it has been pointed out that orientation of Pc molecules is one of key properties that improve the career mobility. We studied orientation property of Si-phthalocyanine thin films using synchrotron radiation. We report on following topics: (1) Orientation analysis using polarized X-rays, (2) Effect of metal substrates and annealing on orientation, (3) Analysis aided by molecular orbital method, and (4) New method to observe chemical-bond directions in nanometer scale using combined techniques of polarized X-ray absorption fine structure (XAFS) spectroscopy and photoelectron emission microscopy (PEEM).

Journal Articles

Real-time observation on surface diffusion and molecular orientations for phthalocyanine thin films at nanometer spacial resolution

Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori; Hirao, Norie; Narita, Ayumi; Deng, J.

Surface Science, 603(16), p.2612 - 2618, 2009/08

 Times Cited Count:6 Percentile:29.57(Chemistry, Physical)

The morphology, electronic structure and ordering for micropatterns of silicon phthalocyanine thin films on gold have been investigated at nanometer scale by photoelectron emission microscopy (PEEM) excited by polarized soft X-rays from synchrotron light source. The incident angle dependences of the X-ray absorption fine structure (XANES) spectra at the silicon K-edge revealed that the molecules of 5-layered films are lying nearly flat on the surface. Clear image of the micropattern was observed by PEEM at room temperature, while the surface diffusion was observed upon heating. On the basis of the photon-energy dependences of the brightnesses in the PEEM images, it was found that the molecules diffusing to the fresh gold surface rather stand-up at 240$$^{circ}$$C. The observed changes in the molecular orientations at nanometer domains are discussed on the basis of the strengths of the molecular-molecular and molecular-surface interactions.

Journal Articles

Formation of C$$_{rm n}$$H$$_{rm x}$$ (n$$geq$$2) molecules from adsorbed methane by low-energy ion irradiation

Narita, Ayumi; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori; Hirao, Norie; Yaita, Tsuyoshi

Hyomen Kagaku, 29(8), p.489 - 494, 2008/08

The formation of molecular ions and neutral molecules from adsorbed CH$$_{4}$$, CD$$_{4}$$ and N$$_{2}$$ following 1 keV He$$^{+}$$ ion irradiation has been investigated. The thickness of the adsorbed layer was precisely controlled. For mono-layered methane, only monomer ions (CH$$_{rm x}$$$$^{+}$$) were desorbed, while a large number of heavy ions (C$$_{rm n}$$H$$_{rm x}$$$$^{+}$$) up to n = 20 as well as heavy neutral molecules (C$$_{rm n}$$H$$_{rm x}$$) were desorbed from multi-layered film. Among the desorbed ions and neutral molecules, molecules with C-C covalent bonds such as acetylene and ethylene were found. The results indicate that chemical bonds are newly formed by ion irradiation. Based on the results for thickness dependences of the mass spectra and calculation of He$$^{+}$$ energy loss process from TRIM-Code, it was elucidated that the monomer ions are desorbed from the top surface layer through single electron excitation. On the other hand, the cluster ions are formed mainly in the inside of the layers along the nuclear track due to phonon excitation, which is produced by nuclear collision between incident He$$^{+}$$ ions and adsorbed molecules.

Journal Articles

Metal-molecular interface of sulfur-containing amino acid and thiophene on gold surface

Honda, Mitsunori; Baba, Yuji; Hirao, Norie*; Sekiguchi, Tetsuhiro

Journal of Physics; Conference Series, 100, p.052071_1 - 052071_5, 2008/03

 Times Cited Count:8 Percentile:91.82

no abstracts in English

Journal Articles

Chemical-state-selective mapping at nanometer scale using synchrotron radiation and photoelectron emission microscopy

Hirao, Norie*; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori

Bunseki Kagaku, 57(1), p.41 - 47, 2008/01

 Times Cited Count:0 Percentile:0.01(Chemistry, Analytical)

For surface analyses of semiconductor devices and various functional materials, it has become indispensable to analyze valence states at nanometer scale due to the rapid developments of nanotechnology. We have developed photoelectron emission microscopy (PEEM) system combined with soft X-rays from synchrotron light source. The samples investigated were Si/SiO$$_{x}$$ micro-patterns prepared by O$$_{2}$$$$^{+}$$ ion implantation in Si(001) wafer using a mask. The lateral spacial resolution of the system was about 41nm. The brightness of each spot in PEEM images changed depending on the photon energy around the Si ${it K}$-edge, due to the X-ray absorption intensity of the respective chemical state. We have also in-situ measured the changes of the PEEM images upon annealing, and elucidated the mechanism of the lateral diffusion of oxygen and valence states of silicon at nanometer scale.

Journal Articles

Chemical-state-selective observations on Si-SiO$$_{rm x}$$ at nanometer scale by photoelectron emission microscopy combined with synchrotron radiation

Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori; Hirao, Norie*; Deng, J.; Narita, Ayumi

Journal of Physics; Conference Series, 100, p.012015_1 - 012015_4, 2008/00

 Times Cited Count:1 Percentile:51.89

Chemical-state-selective mapping of micro-patterns for silicon compounds has been demonstrated using photoelectron emission microscopy excited by soft X-rays from synchrotron light source. The samples investigated were micro-patterns of silicon oxides, silicon nitrides, and organic silicon compounds. By scanning the X-ray energy around the Si $$K$$-edge, we succeeded in observing the sub-micron images depending on the valence states. When we annealed the sample, the lateral diffusion was observed from 700$$^{circ}$$C. During the annealing, however, no intermediate valence states were observed at the Si-SiO$$_{2}$$ interfaces. It was elucidated that the diffusion of oxygen induced the sudden changes of the Si valence states from Si$$^{0}$$ to Si$$^{4+}$$ without any intermediate valence states. The results for the chemical-state-selective mappings and lateral diffusions are also presented for organic silicon compounds.

Journal Articles

Effect of substrates on the molecular orientation of silicon phthalocyanine dichloride thin films

Deng, J.; Baba, Yuji; Sekiguchi, Tetsuhiro; Hirao, Norie*; Honda, Mitsunori

Journal of Physics; Condensed Matter, 19(19), p.196205_1 - 196205_11, 2007/05

 Times Cited Count:6 Percentile:31.38(Physics, Condensed Matter)

Molecular orientations of silicon phthalocyanine dichloride (SiPcCl$$_{2}$$) thin films deposited on three different substrates have been measured by near edge X-ray absorption fine structure (NEXAFS) spectroscopy. For thin films about 5 monolayers, the polarization dependences of the Si K-edge NEXAFS spectra showed that the molecular planes of SiPcCl$$_{2}$$ on three substrates were nearly parallel to the surface. Quantitative analyses of the polarization dependences revealed that the tilted angle on HOPG was only 2 degree, which is interpreted by the perfect flatness of HOPG surface. While the tilted angle on indium tin oxide (ITO) was 26$$^{circ}$$. It is concluded that the morphology of the top surface layer of the substrate affects the molecular orientation of SiPcCl$$_{2}$$ molecules not only for mono-layered adsorbates but also multi-layered thin films.

Journal Articles

Orientation of thin films synthesized from silicon phthalocyanine dichloride on a highly oriented pyrolytic graphite investigated using near edge X-ray absorption fine structure

Deng, J.; Sekiguchi, Tetsuhiro; Baba, Yuji; Hirao, Norie*; Honda, Mitsunori

Japanese Journal of Applied Physics, Part 1, 46(2), p.770 - 773, 2007/02

 Times Cited Count:1 Percentile:5.43(Physics, Applied)

Molecular orientation of thin films of silicon phthalocyanine (SiPc) compounds on highly oriented pyrolytic graphite (HOPG) was investigated by near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS). The films were prepared by a casting method using solution of SiPc dichloride. XPS results showed that the chlorine atoms in SiPc dichloride were substituted by oxygen atoms when the film was heated in the air. The orientation of the molecules with respect to the substrate plane was investigated by the polarization dependences of the Si $$K$$ edge NEXAFS spectra. For the sample heated in the air, two clear peaks appeared in the NEXAFS spectra at around 1847.2 and 1852.4 eV, which were assigned to the resonant excitation form Si 1s to $$sigma$$* orbitals around the Si-N bonds and those around the Si-O bonds, respectively. The intensities of the resonance peaks showed strong polarization dependence. A quantitative analysis of the polarization dependences revealed that the Si-N bond was lying down while the Si-O bond was out of the plane.

Journal Articles

Achievement of high fusion triple product in the JT-60U high $$beta$$$$_{P}$$ H mode

Mori, Masahiro; Ishida, Shinichi; Ando, Toshiro; ; Asakura, Nobuyuki; Azumi, Masafumi; A.A.E.van-Blokland*; G.J.Frieling*; Fujii, Tsuneyuki; Fujita, Takaaki; et al.

Nuclear Fusion, 34(7), p.1045 - 1053, 1994/00

 Times Cited Count:32 Percentile:80(Physics, Fluids & Plasmas)

no abstracts in English

Oral presentation

Chemisorption of amino acid monolayer on gold substrate

Honda, Mitsunori; Baba, Yuji; Hirao, Norie*; Deng, J.; Sekiguchi, Tetsuhiro

no journal, , 

no abstracts in English

76 (Records 1-20 displayed on this page)