S. Emura

The XAFS beamline BL01B1 at SPring-8

aJASRI, SPring-& Mikazuki, Sayo-gun, Hyougo 679-5198, Japan, bRIKEN, SPring-& Kamigori, Ako-gun, Hyougo 6795198, Japan, CjAERI Kansai, SPring-& Mikazuki, Sayogun, Hyougo 679-5143, Japan, dlnstitute of Scientific and Industrial Reseach, Osaka University, Ibaraki, Osaka 5670047, Japan, eFaculty of Science, Okayama University, Okayama 700, Japan, tDepartment of Molecular Engineering, Kyoto University, Kyoto 606-5801, Japan, gFaculty of Science, Osaka University, Toyonaka, Osaka 560, Japan, Fundamental Research Laboratry, NEC, Tsukuba, Ibaragi 305, Japan. Emaihurugat@springS.or.jp

XAFS spectra in the high-energy region measured at SPring-8.

Japan Atomic Energy Research Institute (JAERI Kansai), SPring-8, Mikazuki, Sayo-gun, Hyogo 679-5143, Japan, bThe Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan, CFaculty of Science, Okayama University, Okayama 700-8530, Japan, aFaculty of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan, Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, Mikazuki, Sayo-gun, Hyogo 679-5198, Japan, ~RIKEN, SPring-8, Mikazuki, Sayo-gun, Hyogo 679-5143, Japan. E-mail: yasuon @spring8.or.jp

XAFS in the high-energy region

XAFS (X-ray absorption fine-structure) spectra were measured near K-absorption edges of Ce (40.5 keV), Dy (53.8 keV), Ta (67.4 keV) and Pt (78.4 keV). The blunt K-edge jump due to the finite lifetime of the core hole was observed. This makes it difficult to extract EXAFS (extended X-ray absorption fine-structure) functions at low k values. Local structure parameters can be evaluated from the EXAFS spectra above K-absorption edges in the high-energy region as well as from those above L(III)-edges. It was found that the finite-lifetime effect of the core hole is effectively taken into the photoelectron mean-free-path term, as predicted theoretically.

EXAFS spectra above Pb and Pt K edges observed at low temperature

X-ray absorption spectra near K edges of Pb (88.0keV) and Pt (78.4keV) for the foils were measured in transmission mode at SPring-8. We succeeded for the first time in observing the EXAFS oscillation of the Pb foil at 12K, although it was failed at room temperature in a previous experiment. The amplitude of the EXAFS oscillation of the Pt foil at 12K considerably increased in comparison with that at room temperature, indicating that the amplitude is very sensitive to the Debye-Waller factor at high-k values.

Temperature dependence of local structure of Rb2CsC60 superconductor

EXAFS studies on Rb3C60 are made as a function of temperature from 6K to 300 K. It is found that the distance rRb-c and the second, third and fourth cumulant terms of Debye-Waller factors, σ(2), σc(3) and σc(4), show the anomalous behavior near Tc.

XAFS study of bcc fullerene compounds, Rb6C60, Ba6C60 and K3Ba3C60

Abstract Rb K-edge XAFS of Rb 6 C 60 and Ba K-edge XAFS of Ba 6 C 60 and K 3 Ba 3 C 60 have been studied, all of which take a bcc structure. The radial structure functions obtained by Fourier transform of XAFS spectra for these compounds showed two pronounced envelopes which can be attributed to the scattering between metal ion and the neighboring C atoms and that between metal ions. The mean-square-displacements for the metal-C in these compounds were larger than that for the t-site Rbue5f8C in Rb 3 C 60 because of the distribution in metal-C distances. From the temperature dependent XAFS, it has been found that the mean-square-displacement for Rbue5f8C in a non-superconductor Rb 6 C 60 shows no anomaly around superconducting transition temperature, contrary to a superconductor Rb 3 C 60 .

Local Structure Around Cs+Ion In Rb2CsC60

ABSTRACT Local structure around Cs+ ion in Rb2CsC60 has been investigated on the basis of Cs K-edge EXAFS spectrum. It has been found that Cs+ ions are located mainly in the octahedral site. The fraction of Cs+ ions in the tetrahedral and octahedral sites has been determined.

Local lattice instability of cuprous ions in NaBr and NaCl

The local lattice instability around the imperfection doped in the host matrix is investigated with ultra-violet absorption spectra and x-ray excitation spectra. The local environment of a cuprous ion in NaCl shrinks, and in NaBr cuprous ion is lacated away from the regular lattice site. This phenomenon is discussed with the pseudo Jahn–Teller effect.

Acceleration of halogen-exchange reaction of lead(II) fluoride in organic solvent.

Acceleration of halogen-exchange reaction of lead(ll) fluoride in organic solvent compound 1 has not high activities for the organic fluorination as well as PbF 2, another species for inducing the organic reaction should exist in the combined process of NaBr and PbF 2. Not only reaction species but also reaction process remains ambiguous, because the active species arising from a small amount of sodium bromide seems to be small and such species could not have the long range ordering. Thus the XAFS investigation has been carried out to elucidate the active species for the present combined NaBrPbF 2 reagent.

Temperature-dependent EXAFS study on oriented YBa2Cu3O7−δ superconductor

Abstract The polarized Cu K-edge EXAFS measurements on oriented powder of YBa 2 Cu 3 O 7−δ ( T c = 93 K, 5 μm grain size) are made as a function of temperature from 20 to 300 K for the a − b plane and the c axis being parallel to the X-ray polarization vector ϵ. Here, we focus on the local structure of Cuue5f8O bonds in the a − b planes. It is found that the average Cuue5f8O (equalatorial) distance and cumulants in the CuO 4 square plane show anomalous behaviors around T c .