Sei Fukushima

Spatial harmonic rejection in a large offset rotated-inclined double crystal monochromator at BL15XU in SPring-8

A 100mm offset rotated-inclined double crystal monochromator has been installed at BL15XU in SPring-8. The spatial profiles of the exit X-ray beam by using Si(1 1 1) in inclined geometry was measured from 5 to 20keV. The vertical deviation, due to refraction, between the first and the higher order was more than 0.7mm. The large deviation enables to eliminate the higher-order reflections by spatial screening with horizontal blade slits. The intensity ratio of the higher-order reflection to the first order was less than 10−5 over the whole energy range.

Performance of YB66 double-crystal monochromator for dispersing synchrotron radiation at SPring-8

Abstract In the 1–2xa0keV range, we adopted YB 66 crystal for dispersing synchrotron radiation of the beamline No.15 (BL15XU) at SPring-8. YB 66 crystal has a large d -value of 0.586xa0nm for the 4xa00xa00 reflection and is useful as a soft X-ray monochromator for dispersing synchrotron radiation, since there is no intrinsic absorption edge and it is more resistant than other crystals to synchrotron radiation damage. We investigated the resolution of the YB 66 double-crystal monochromator and measured the photon flux passing through this monochromator. The full-width at half-maximum of the rocking curve ranged from 0.15xa0eV at 1.1xa0keV to 0.42xa0eV at 2.1xa0keV. The photon flux ranged from 6×10 8 xa0photons/sec/100xa0mA measured at an experimental position at 1.1xa0keV to 5×10 9 xa0photons/sec/100xa0mA measured at an experimental position at 2xa0keV. It is considered that the better energy resolution of the YB 66 crystal was achieved by irradiating only a small restricted area of the crystal by an incident beam with small angular divergence originated from a helical undulator.

Relation between x-ray emission mechanism and crystal structure in LiNbO3

x-ray emission in LiNbO3 is confirmed by thermal treatments in a vacuum system by a new cleaning method of the crystal. Detailed single-crystal high-temperature x-ray structure refinements were carried out at 297, 323, 373, 423 and 473 K, far below the phase transition (~1473 K). The unit cell dimensions a and V show a linear increase with temperature; however, the lattice parameter, c shows only a slight linear increase. The length of Nb–O bonds in adjacent octahedra is almost constant below 423 K. It is suggested that the valence electron in Nb changes in the compound. Therefore, x-ray emission induced by charged particles including electrons can be considered to have a close relation to the electric charge of Nb in LiNbO3.

Threshold excitation in fe kα3,4 satellites

Fe Kα3,4 satellite spectra are investigated using a Johann-type spectrometer at the BL15XU undulator beam line, SPring-8. The intensity of the Kα3,4 satellite relative to the Kα1 emission line is found to increase asymptotically with excitation energy up to 9000 eV, almost saturating at 10 000 eV. The satellite threshold energy is found to be 7882 ± 14 eV. This corresponds to the ionization energy of Fe 1s + 2p*, where * indicates that the value is from the Z + 1 approximation. The appearance of a small peak around the [1s2s] double ionization energy suggests that the satellite intensity with the excitation energy can be increased not only by the formation of the 2p spectator holes, but also by a combination of the [1s2s] resonance and [2s2p] Coster–Kronig transition.

Preparation of Bi2Sr2Can−1CunOy superconducting films by a rf magnetron sputtering method with multi-targets

Abstract We prepared Bi2Sr2Can−1CunOy films by a rf magnetron sputtering method with two targets of Bi:Sr:Cu=4.3:1.8:0.6 and Ca:Cu=2:1, where the sputtering gas of helium and oxygen, and an off axis geometry were used. The Bi2Sr2CuOy and Bi2Sr2CaCu2Oy (Bi-2212) films were c-axis-oriented and the full-width-half-maximum value of X-ray diffraction (0xa00xa0 10 ) peak due to a Bi-2212 superconductor was about 0.4°. The film showed the on-set superconducting transition at about 94 K. The use of two targets, Bi–Sr–Cu–O and Ca–Cu–O is thought to be useful for the growth of high quality Bi2Sr2Can−1CunOy films.

XPS study on the Bi-2212 single crystals grown by a modified vertical Bridgman method

Abstract We carried out surface cleaning of Bi 2 Sr 2 CaCu 2 O y (Bi-2212) single crystals grown by a modified vertical Bridgman method (modified VB method), and investigated the chemical state with X-ray photoelectron spectroscopy. From the results, we found that carbon impurities on the surface of the single crystals were mostly removed by cleaving them in the high vacuum (7.3xa0×xa010 −6 Pa). The O-1s peak from the cleaved surface of the single crystal was very sharp and its FWHM value was about 2.0 eV. Moreover, we knew that the crystals did not include any carbon impurities, and that they had few mutual substitutions between Ca and Sr. Therefore, the single crystals grown by a modified VB method is expected to have a high quality.

A study of the appearance of Li Kα

Using electron beam excitation, Li K? of insulator samples, such as oxides other than LiF, is impossible, or very hard to detect. Metallic Li, on the other hand, is easy to observe. Therefore, an examination using cluster calculation was carried out. From the calculation results, it was revealed that the Li K? of LiF obtained by our measurement did not correspond to the correct state of Li in LiF. This spectrum might be emitted from the Li atom which was reduced and changed to the metallic state due to the electron beam irradiation. It was also suggested that the existence of the conduction electron at valence might easily cause the dipole transition process for the relaxation of the hole on the shallow core hole. Such a hole is generally relaxed by the Auger relaxation process.

High‐Resolution Anti‐Parallel Double‐Crystal Spectrometer at BL15XU in SPring‐8

A simple double‐crystal spectrometer with an anti‐parallel setting was developed in the third generation synchrotron facility BL15XU, SPring‐8. This is derived by modifying the commercial RIGAKU Spectrometer (3580E). Although the resolving power of the two‐crystal x‐ray spectrometer is largely dependent on the perfection of the crystals, the x‐ray spectrometer secures high resolving power, intensity, and reproducibility. This system is convenient for the experiment of Resonant Inelastic X‐ray Scattering (RIXS). As an example, RIXS data of several elements in ferroelectric materials LiTaO3 and BaTiO3 and XAS spectra of Cu metal and Cu oxide are presented.

Satellites hidden by diagram lines in heavy elements Ir, Pt, Au

Hidden satellites due to Coster–Kronig transitions have a characteristic threshold energy in their appearance and hence can be identified by looking at spectra at either side of the threshold. To investigate the hidden satellites, we measured Lβ2,3,15 spectra of Ir, Pt and Au below and above the L1 edge. The measured spectra were normalized using Lβ1 spectra. The existence of hidden satellites was confirmed by observing the differences between the normalized spectra above and below the L1 edge.

Rocking Curve Calculation for YB66 Crystal

The rocking curves of a YB66 crystal were calculated in the wide energy range of 1–2 keV using the method that Lee developed. The results show that the energy resolution δE is 0.061 eV and the peak reflectivity is 12.0% at the photon energy of 1.1 keV, and that the energy resolution δE is 0.053 eV and the peak reflectivity is 32.8% at the photon energy of 2.025 keV. In the entire energy range of 1–2 keV, the energy resolution δE is 0.061 eV or less and the peak reflectivity is 12.0% or more, with the peak reflectivity having a maximum at around 1.9 keV. The calculated structure factors of the YB66 crystal indicated that YB66 has a strong 400 diffraction due to its characteristic structure in which Y atoms are arranged on the (400) crystal plane or near the (000) and (200) crystal planes.