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-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.
Nagao, Tatsuya*; Igarashi, Junichi
Journal of the Physical Society of Japan, 72(9), p.2381 - 2384, 2003/09
Times Cited Count：10 Percentile：54.95(Physics, Multidisciplinary)We examine the mechanism of the X-ray diffraction process by including the Thomson scattering (TS) term in addition to the resonant X-ray scattering (RXS) term near the Ce L absorption edge in the antiferroquadrupole (AFQ) ordering phase of CeB. Assuming the AFQ order in the 4f states but without any lattice distortion, we obtain the TS intensity comparable to the RXS intensity, owing to the anisotropic charge distribution of 4f states. The present calculation reproduces well the interference pattern between the TS and RXS terms for the (5/2,3/2,3/2) spot observed in the recent experiment. The result suggests that the TS signal as well as the main peak of the RXS signal are a direct reflection of the AFQ order in CeB.
CIgarashi, Junichi; Nagao, Tatsuya*
Journal of the Physical Society of Japan, 72(5), p.1279 - 1286, 2003/05
Times Cited Count：13 Percentile：61.07(Physics, Multidisciplinary)We study the resonant X-ray scattering (RXS) spectra at the Dy L_
absorption edge in the quadrupolar ordering phase of DyBC. Analyzing the buckling of sheets of B and C atoms, we construct an effective model that the crystal field is acting on the 5d and 4f states with the principal axes different for different sublattices. Treating the 5d states as a band and the 4f states as localized states, we calculate the spectra within the dipole transition. We take account of processes that (1) the lattice distorion directly modulates the 5d states and (2) the charge anisotropy of the quadrupole ordering 4f states modulates the 5d states through the 5d-4f Coulomb interaction. The former process is found to give dominant contribution to the spectra.
