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Baba, Yuji; Shimoyama, Iwao
Photon Factory Activity Report 2016, 2 Pages, 2017/00
In order to elucidate the adsorption states of radioactive Sr-90 in soil, chemical bonding states of non-radioactive strontium adsorbed on layered oxide (mica) have been investigated by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) spectroscopy. Since the number of atoms in radioactive Sr-90 is extremely small, the XPS and XANES were measured under total reflection condition of the incident X-rays. The detection limit in total reflection XPS was about 150 pg/cm
, which corresponds to 300 Bq of Sr-90. The Sr 2p
core-level energy in XPS shifted to lower energy with the decrease in the thickness of Sr layer. Also, the Sr 2p 
Sr 4d
resonance energy in XANES shifts to lower energy with the decrease in the thickness. On the basis of a simple point charge model, it was elucidated that the chemical bond between Sr and mica surface becomes ionic with the decrease in the adsorbed amount of strontium.
-irradiated graphite surfaces using photon-stimulated desorption spectroscopySekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Nath, K. G.
Surface and Interface Analysis, 38(4), p.352 - 356, 2006/04
Times Cited Count：3 Percentile：7.13(Chemistry, Physical)We investigated the orientation nature at the top-most layers of F-irradiated graphite using polarization dependent near-edge X-ray absorption fine structure (NEXAFS) spectroscopy which incorporates partial electron yield (PEY) detection and photon-stimulated ion desorption (PSID) techniques. The fluorine K-edge NEXAFS spectra conducted in PEY mode show no significant dependence on polarization angles. In contrast, NEXAFS spectra recorded in F ion yield mode show enhanced yields at a feature of 
689.4 eV assigned as a 
*(C-F) state relevant to =C-F sites, which depend on polarization angles. The C-F bonds prefer relatively tilting down the surface at the top-most layer, while the C-F bonds are randomly directed at deeper regions. We conclude that the difference in the orientation structures between the top surface and bulk is reflected in the NEXAFS recorded in the two different detection modes. It was also found that H- and F
- PSID NEXAFS spectra are helpful in understanding desorption mechanism, thus in analysing NEXAFS data.
Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Wu, G.*; Kitajima, Yoshinori*
Surface Science, 593(1-3), p.310 - 317, 2005/11
Times Cited Count：2 Percentile：11.64(Chemistry, Physical)Using a newly developed rotatable time-of-flight mass spectrometer(R-TOF-MS) and polarized synchrotron radiation, orientation effect on fragmentation and desorption pathways occurring at the top-most layers of molecular solids have been investigated. Reported will be polarization-angle dependencies of TOF mass spectra, high-resolution electron- and ion-NEXAFS in condensed chlorobenzene.
Ikeura, Hiromi*; Sekiguchi, Tetsuhiro; Baba, Yuji; Imamura, Motoyasu*; Matsubayashi, Nobuyuki*; Shimada, Hiromichi*
Surface Science, 593(1-3), p.303 - 309, 2005/11
Times Cited Count：5 Percentile：26.1(Chemistry, Physical)no abstracts in English
)SiX (X = F, Cl, Br, I, NCO) as studied using NEXAFS spectroscopySekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Nath, K. G.*; Uddin, M. N.*
Journal of Physics; Condensed Matter, 17(36), p.5453 - 5466, 2005/09
Times Cited Count：1 Percentile：6.21(Physics, Condensed Matter)The orientation nature of multilayer organosilicon compounds has been investigated by measuring the dependence of the Si K-shell near-edge X-ray absorption fine structures (NEXAFS) on the polarization angle. Two approaches helped to elucidate the orientation mechanism: the substitution effect and the deposition-rate dependence. The orientation angles of Si-X bond axes were obtained for trimethylsilyl halides, (CH)SiX (X =F Cl Br I NCO, condensed on Cu(111) at a low (82 K) temperature: the angles are 60, 73, 61, 55, and 55 degrees with respect to the surface normal, for X =F, Cl, Br, I, and NCO, respectively. Chloride (X =Cl) produces the most parallel tilt angle. The specific orientation nature of chloride is attributed to its strong dipole moment as well as the regular tetrahedron shape of the molecule. The molecular volumes calculated verify this view. Furthermore, deposition rates are found to greatly influence the growth manner: namely, high deposition rates led to a slightly perpendicular orientation of Si-X bond axis.
Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro
Proceedings of 16th International Corrosion Congress (CD-ROM), 6 Pages, 2005/09
XANES measurements of rust layers formed on Fe, Fe-Cr alloys and Fe-Ni alloys exposed to a Cl-rich atmosphere have been performed using synchrotron radiation in order to clarify the relation between the structural properties of the rust layer on weathering steel and anticorrosive alloying elements and/or chloride ions. The XANES spectra around Cl K-edge revealed that the rust layer on the Fe-based binary alloys contains unidentified chloride in addition to akagan
iteite. The Fe K-edge XANES results indicated that the rust layers are composed mainly of well-known iron oxides, goethite, akaganite, lepidocrocite and magnetite. In particular, the mole ratio of akaganite in the rust layers on the Fe-Ni alloys is relatively higher than that of the Fe-Cr alloys. The Cr K-edge XANES spectra of the rust layers on the Fe-Cr alloys depends on the Cr alloy content. Therefore, the local structure of Cr in the rust layer is variable with the Cr density. In contrast, the Ni K-edge XANES results show that the local structure of Ni in the rust layer are unique in a certain Ni content range.
Nath, K. G.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji
Journal of Electron Spectroscopy and Related Phenomena, 144-147, p.323 - 326, 2005/06
Times Cited Count：5 Percentile：27.33(Spectroscopy)The effect of laser annealing on electronic atructures and molecular orientation for poly(dimethylsilane), {PDMS, [Si(CH)
]
} has been studied by synchrotron radiation photoemission and photoabsorption spectroscopy. Prior to annealing, PDMS powder was mounted on the basal plane of highly oriented pyrolytic graphite. Both Si 1s X-ray photoemission spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at Si 1s edge show that electronic structures have been modified due to annealing. Furthermore, the angle-dependent NEXAFS spectra clearly indicate that the annealed products maintain a specific orientation. Interestingly, no such kind of orientation is present in as-received PDMS powder as no angle-dependency is observed before annealing.
Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro
Materials Transactions, 46(2), p.329 - 336, 2005/02
Times Cited Count：28 Percentile：80.32(Materials Science, Multidisciplinary)Chloride in atmosphere considerably reduces the corrosion resistance of conventional weathering steel containing a small amount of Cr. Ni is an effective anticorrosive element for improving the corrosion resistance of steel in a Cl-rich environment. In order to clarify the structure of the protective rust layer of weathering steel, Cl and Fe K-edge X-ray absorption near edge structure (XANES) spectra of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich atmosphere were measured. The Fe K-XANES measurements enable the characterization of a mixture of iron oxides such as rust. The chemical composition of the rust was determined by performing pattern fitting of the measured spectra. All the rust is composed mainly of goethite, akaganite, lepidocrocite and magnetite. Among these iron oxides, akaganite in particular is the major component in the rust. Additionally, the amount of akaganite in the rust of Fe-Ni alloy is much greater than that in rust of Fe-Cr alloy. Akaganite is generally considered to facilitate the corrosion of steel, but our results indicate that akaganite in the rust of Fe-Ni alloy is quantitatively different from that in rust of Fe-Cr alloy and does not facilitate the corrosion of steel. The shoulder peak observed in Cl K-XANES spectra reveals that the rust contains a chloride other than akaganite. The energy of the shoulder peak does not correspond to that of any well-known chlorides. In the measured spectra, there is no proof that Cl, by combining with the alloying element, inhibits the alloying element from acting in corrosion resistance. The shoulder peak appears only when the content of the alloying element is lower than a certain value. This suggests that the generation of the unidentified chloride is related to the corrosion rate of steel.
Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro
Materials Transactions, 45(12), p.3356 - 3359, 2004/12
Times Cited Count：10 Percentile：53.05(Materials Science, Multidisciplinary)Cl K-edge XANES measurements of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys in chloride pollution have been performed using synchrotron radiation in order to clarify roles of anticorrosive alloying elements and of Cl in the corrosion resistance of weathering steel. The spectra of binary alloys show a shoulder structure near the absorption edge. The intensity of the shoulder peak depends on the kind and amount of the alloying element, whereas the energy position is invariant. This indicates that Cl is not combined directly with alloying elements in the rust.
at the Si 1s edgeBaba, Yuji; Sasaki, Teikichi; Yamamoto, Hiroyuki
Physical Review B, 49(1), p.709 - 711, 1994/01
Times Cited Count：47 Percentile：86.42(Materials Science, Multidisciplinary)no abstracts in English
Baba, Yuji; Yamamoto, Hiroyuki; Sasaki, Teikichi
Surface Science, 307-309, p.896 - 900, 1994/00
Times Cited Count：29 Percentile：83.34(Chemistry, Physical)no abstracts in English
(0
x2) and SiN (0x4/3) produced by low-energy ion implantation in Si(100)Baba, Yuji; Yamamoto, Hiroyuki; Sasaki, Teikichi
Physical Review B, 48(15), p.10972 - 10977, 1993/10
Times Cited Count：25 Percentile：77.19(Materials Science, Multidisciplinary)no abstracts in English
and SiN by surface XANESBaba, Yuji; Yamamoto, Hiroyuki; Sasaki, Teikichi
Hyomen Kagaku, 14(5), p.260 - 264, 1993/00
no abstracts in English
Yomogida, Takumi; Higashi, Kotaro*; Kawamura, Naomi*; Kitatsuji, Yoshihiro; Takahashi, Yoshio*
no journal, ,
Biotite, a layered silicate mineral, is known to be a host phase for uranium(U) in U mines. There are still many unclear factors regarding its U accumulation mechanism. In this study, U adsorption experiment was conducted on artificially weathered biotite by removing interlayer potassium. The results showed that the ratio of reduced species of U increased with increasing the K loss ratio in interlayer, indicating that U reduction occurred at cleavages developed by weathering of the biotite.
