On the surface chemical reactions of metal and oxide XPS samples at 300–400° at a high vacuum produced by oil diffusion pumps

Metal and oxide surface reactions formed by heating in the spectrometer at 300–400° at a vacuum of ca. 10^?9 Torr (oil diffusion pumps) were studied. As a result of spectral observations before and after heating, the metals studied were classified into five groups. In the first group, oxide films on the metal surface are easily evaporated because of the high vapour pressure of oxide; in the second, the oxide films are easily reduced in the spectrometer; in the third, the oxide film formed on the metal is reduced but the bulk oxide is not easily reduced; in the fourth, very stable oxide films are formed and the bulk oxide is also stable; and finally in the fifth, the oxide film formed on the metal is apparently reduced, yet the bulk oxide is very stable.     

Perfluorinated polymer film with functional group prepared by radiation-induced grafting

A perfluorinated vinyl ether monomer, 2-bromotetrafluoroethyl trifluorovinyl ether (BrTFF) was grafted into crosslinked poly(tetrafluoroethylene) (cPTFE) films by γ-rays irradiation under different conditions. The irradiation with absorbed doses more than 550 kGy gave the poly(BrTFF) grafted cPTFE membranes with grafting yields of more than 20%. FTIR spectra and SEM-EDS testified that BrTFF was successfully grafted into cPTFE films homogeneously in the film perpendicular direction. TGA analysis of the grafted films indicated that the perfluorinated poly(BrTFF) grafts were phase-separated from the PTFE region due to the crosslinked structure of the cPTFE based film, but the grafted films still had high thermal stability (above 300 °C). DSC measurements showed the decrease of melting temperature, but the increase of both heat of fusion and degree of crystallinity in cPTFE film after grafting. The grafted film, a new kind of perfluorinated polymer with bromine active groups and good mechanical properties, is expected to be modified for new applications.     

Comparison of intrinsic zero-energy loss and Shirley-type background corrected profiles of XPS spectra for quantitative surface analysis: Study of Cr, Mn and Fe oxides

The intrinsic zero-energy loss profiles of transition metal 2p and 3p XPS spectra for Cr, Mn, and Fe oxides are obtained by spectral deconvolution and compared with Shirley-type background corrected profiles. The metal core level spectra are deconvoluted by O 1s spectra as the response function of each oxide. As the O 1s spectra include intrinsic and extrinsic energy loss parts, the background corrected core level spectra are zero-energy loss spectra. The good agreement of the deconvoluted spectra with the reported spectra obtained by the many body effect theory indicates that the background subtraction method is accurate. A comparison of the deconvoluted with the background corrected spectra of the Shirely-type subtraction reveals that almost all the spectra coincide with each other except for Fe 3p with -Fe₂O₃. The good coincidence of the Shirley-type corrected spectra with the deconvoluted and calculated spectra indicates that Shirley-type background correction can be used for daily quantitative surface analysis.     

Design of a neutron polarizer using polarizing super mirrors for the TOF-SANS instrument at the J-PARC

Small-angle neutron scattering technique using polarized neutrons is powerful for studying structures in the range between nm and μm of magnetic materials. In addition, they have been used for the incident beam of focusing-geometry SANS instruments using a magnetic neutron lens, where a high polarization degree of about 99.9% is necessary because the imperfectness of the neutron polarization increases the background level. We are going to install such a magnetic focusing system on the new time-of-flight SANS (TOF-SANS) instrument at the J-PARC so as to make q_min smaller than 10⁻³ Å⁻¹ and improve the resolution of the conventional TOF-SANS at low q. As a polarizing device of the instrument, two V-shaped polarizing super mirrors arranged in crossed geometry to enhance the polarization degree has been considered. In this paper, we present the concept and the detailed design of this device and its performance estimated by Monte Carlo simulations.     

Development of modulating permanent magnet sextupole lens for focusing of pulsed cold neutrons

Modulating permanent magnet sextupole lens (PMSx) for focusing pulsed cold neutrons is under development. The synchronized modulation of its field gradient suppresses the chromatic aberration which arises from the Time Of Flight method. The strength of the magnetic field, the torque, and the rise of temperature during its operation are studied on a fabricated prototype. Experiments on focusing pulsed very cold neutrons (VCN) at ILL (Institute of Laue Langevin, France) were carried out and VCN with around λ=40 Å were focused by the PMSx at a focal length of about 0.5 m. The experimental results are presented in conjunction with the principle of the neutron focusing and the modulating method of the focal strength of permanent magnet lens with the double ring structure.     

Diastereo‐ and Enantioselective Synthesis of (E)‐δ‐Boryl‐Substituted anti‐Homoallylic Alcohols in Two Steps from Terminal Alkynes

We report the highly diastereo‐ and enantioselective preparation of (E)‐δ‐boryl‐substituted anti‐homoallylic alcohols in two steps from terminal alkynes. This method consists of a cobalt(II)‐catalyzed 1,1‐diboration reaction of terminal alkynes with B₂pin₂ and a palladium(I)‐mediated asymmetric allylation reaction of the resulting 1,1‐di(boryl)alk‐1‐enes with aldehydes in the presence of a chiral phosphoric acid. Propyne, which is produced as the byproduct during petroleum refining, could be used as the starting material to construct homoallylic alcohols that are otherwise difficult to synthesize with high stereocontrol.     

Production of the X( 3872) in B-meson decay by the coalescence of charm mesons

If the recently discovered charmonium state X( 3872) is a loosely bound S-wave molecule of the charm mesons D0 D(*0) or D(*0) D0, it can be produced in B-meson decay by the coalescence of charm mesons. If this coalescence mechanism dominates, the ratio of the differential rate for B+ -->D(0) D(* 0)K+ near the D0 D(*0) threshold and the rate for B+ -->XK+ is a function of the D0 D(*0) invariant mass and hadron masses only. The identification of the X( 3872) as a D0 D(*0)/D(*0)D0 molecule can be confirmed by observing an enhancement in the D0 D(*0) invariant mass distribution near the threshold. An estimate of the branching fraction for B+ -->XK+ is consistent with observations if X has quantum numbers J(PC)=1(++ ) and if J/psi pi(+) pi(-) is one of its major decay modes.     

X-ray photoelectron spectroscopic studies on phase identification and quantification of nickel aluminides

Core-level XPS spectra for clean surfaces of Ni₃Al, NiAl, and NiAl₃ alloys were studied. The clean surfaces were obtained by fracturing in the ultra-high vacuum chamber. The positive chemical shifts of Ni 2p_3/2 peak for NiAl and NiAl₃ from Ni metal were 0.2 and 1.0 eV, respectively. The negative shift for Al 2p peak and the positive shift for Ni 3p peaks increased with the decreasing concentration of the corresponding elements. The peak position of the bulk plasmon loss peak for Al 2s peak shifted toward higher energy side, and further, the intensity ratio decreased with the decrease in aluminum concentration. Both the peak intensity ratios of Al 2p to Ni 3p determined by factor analysis and convenient separation are proportional to the atomic ratio of aluminum to nickel. The results indicate that the intensity ratio of Al 2p to Ni 3p determined by these two methods can be applied to the quantification for the surface of the nickel-aluminum alloys.