Yohichi Gohshi

Analysis of trace Co in synthetic diamonds using synchrotron radiation excited X-ray fluorescence analysis

Abstract Synchrotron radiation excited X-ray fluorescence analysis was utilized for characterization of trace impurities in synthetic diamonds. Advantage of the energy tunability was fully utilized to evaluate the attenuation of X-rays through the sample, and the absorption corrected X-ray fluorescence yield was utilized for quantitative analysis. Diamonds grown with several types of metallic solvents were investigated, and quantitative analysis of trace Co was carried out. It was found that Co prefers to be dissolved into {1 1 1} growth sector and that Co concentration in the {1 1 1} growth sector decreases one order of magnitude with the existence of Ni in the solvent. XANES spectra of dissolved Co shows characteristic pre-edge feature similar to that reported with the dissolved Ni. Experimental results suggest that both Ni and Co occupy in the similar site in the diamond lattice and that Ni is easier to be dissolved into diamonds.

Chemical shift and lineshape of high-resolution Ni Kα x-ray fluorescence spectra

Nickel K-L (Kα) x-ray fluorescence spectra of 32 kinds of materials containing nickel [NiF 2 , NiSO 4 , Ni(CO 3 ) 2 , Ni(OH) 2 , Ni 2 O 3 , NiTiO 3 , NiO, NiFe 2 O 4 , NiCl 2 , NiBr 2 , NiI 2 , LiNiO 2 , NiS, NiTe, Ni 3 P, metal, LaNi 5 , Ni 2 P, NiCr, Ni 2 Si, NiB, NiSi 2 , acetylacetonate, K 2 Ni(CN) 4 , and some nickel complexes] were measured using a double-crystal x-ray fluorescence spectrometer. The shift, asymmetry and spin-orbit splitting energy were extracted from the measured spectra. The asymmetric Kα lineshape was deconvoluted by Lorentzian functions. It is demonstrated that the chemical state of nickel in an unknown material can be analyzed by the use of these parameters.

High resolution soft X-ray absorption spectroscopy for the chemical state analysis of Mn

Abstract Mn L 2,3 X-ray absorption spectra of various manganese compounds were measured using a synchrotron radiation facility. Very high-resolution spectra were obtained. Sharp lines, which were not found before, were observed, and reproducibility was checked using a different beam line in the synchrotron radiation facility. Difference in spectral line shape was observed as the difference of quantum yield method. An unknown sample was measured and the specimen was concluded to be a mixture of two different oxidation states of Mn. The effects on the change of spectral profiles are discussed.

Data Processing for Obtaining Atomic Images from SrTiO3 X-Ray Fluorescence Hologram

It is difficult to obtain a clear atomic image from a measured X-ray fluorescence hologram, because the holographic undulation in the angular distribution of the X-ray fluorescence intensity is feeble. We introduce here our numerical data process to reconstruct an atomic image from the SrTiO3 (001) hologram data reported in a previous paper [J. Kawai et al..: Anal. Sci. 14 (1998) 903]. The holographic oscillation, which could not be seen in the raw data, was revealed by the Savitzky-Golay smoothing method. We also considered the effect of the hologram size on the reconstructed image of Sr atoms, and found that the spatial resolution of the image became higher with an increase of the size in the hologram.

K X-ray emission spectra of Ni in nickel(II) Schiff base complexes

K x-ray emission spectra of Ni were measured in bis(N-isopropylsalicylideneaminato)nickel(II) and bis(N-isobutylsalicylideneaminato)nickel(II) with different types of coordination, planar or pseudo-tetrahedral, using a double-crystal x-ray spectrometer. The relationship between the magnetic susceptibility and the energy spectra of the Kβ2,5 and Kβ′ emission lines was investigated for these compounds. The electronic structures of the compounds were also studied by the use of the molecular orbital method. Copyright

A compact x-ray beam intensity monitor using gas amplified sample current measurement

Development of a compact beam intensity monitor using gas amplified sample current measurement is described. The monitor can be a powerful tool for x-ray spectroscopy and microscopy when the beam is defined by a small pinhole or slits and when the workspace around the sample is limited. The thickness of the monitor is as small as approximately 3 mm, and the dimension is 10 mm square. The photon flux is monitored by measuring x-ray excited current from an Al foil under atmospheric conditions. Emitted electrons from the Al foil can ionize surrounding air molecules, and the gas amplified current can be measured with the use of a biased grid that prevents created ion pairs from recombination.

Difference in the tunnel current-tunnel gap width dependence of molecule-adsorbed and non-adsorbed graphite measured by means of tunnel gap imaging

Abstract The tunnel gap imaging (TGI) technique is used to measure local tunnel current ( I ) to tunnel gap width ( s ) dependences (the I–s characteristics) of molecule–adsorbed and non–adsorbed surface of highly orientated pyrolytic graphite under atmosphere. When the bias voltage of several hundreds of millivolts were applied to the sample, the I–s characteristics of molecule–adsorbed sample exhibited clear bending while those of non–adsorbed sample did not. The I–s characteristics at small s region were found to be similar to those of non–adsorbed sample, but those at large s regions were absolutely different. Barrier heights calculated from the I–s characteristics at large s region for the molecule–adsorbed sample were found to be 2 or 3 orders lower than those at small s region were. The tunnel current dominant at large s region was estimated to be the inelastic tunnel current by its bias voltage dependence. The mechanism of molecular image formation in STM is discussed based on the presence of the inelastic tunnel current.

Spectromicroscopy using an x-ray microprobe at SPring-8 BL39XU

Brilliant undulator radiation from a super photon ring 8 GeV (SPring-8) is utilized for spectromicroscopy in hard x-ray region. Design parameters of the x-ray microprobe dedicated for BL39XU are described. X-ray beam less than 1 μm is expected by using a Kirkpatrick and Baez mirror system, and both conventional and high resolution x-ray fluorescence spectrometers are available by using a Si(Li) detector and a wavelength dispersive spectrometer equipped with a flat analyzer crystal and a PSPC. Preliminary experimental results of the x-ray microprobe system show possibilities of trace characterization with spatial resolution.