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Depth profiling of sucrose thin films was investigated with time-of-flight secondary ion mass spectrometry (TOFSIMS) using 10 keV [C.sub.60.sup.+], 20 keV [C.sub.60.sup.2+], and 30 keV [C.sub.60.sup.3+], and 250, 500, and 1000 eV [Cs.sup.+] and [O.sub.2.sup.+] as sputtering ions. With [C.sub.60.sup.n+] ions, the molecular ion signal initially decreases and reaches a steady state that is about 38-51% of its original intensity, depending on the energy of the [C.sub.60.sup.n+] ions. In contrast, with [Cs.sup.+] and [O.sub.2.sup.+] sputtering, molecular ion signals decrease quickly to the noise level, even using very low-energy (250 eV) ions. In addition, the measured width of the sucrose/Si interface is much narrower using [C.sub.60.sup.-] ions than that using [Cs.sup.+] or [O.sub.2.sup.+] ions. To understand the mechanisms of sputtering-induced damage by these ions, X-ray photoelectron spectroscopy CAPS) and atomic force microscopy (AFM) were used to characterize the bottoms of these sputter craters. XPS data show very little chemical change in the [C.sub.60.sup.+] sputter crater, while considerable amorphous carbon was found in the [O.sub.2.sup.+] and [C.sup.+] sputter craters, indicating extensive decomposition of the sucrose molecules. AFM images show a very flat bottom in the [C.sub.60.sup.+] sputter crater, while the bottoms of the [Cs.sup.+] and [O.sub.2.sup.+] sputter craters are significantly rougher. We used the sputtering model developed by Wucher and co-workers to quantitatively analyze our [C.sub.60.sup.1-3+] data. The results show that low energy [C.sub.60.sup.+] ions generate a relatively thin damage layer with a high molecular ion signal, suggesting that low energy [C.sub.60.sup.+] may be the optimal choice for molecular depth profiling of sucrose films. 10.1021/ac900553z

Aluminum coordination in the framework of USY and ZSM-5 zeolites containing charge-compensating cations {N[H.sub.4][.sup.+], [H.sup.+], or [Cu.sup.+]} was investigated by Al K-edge EXAFS and X-ray absorption near edge spectroscopy (XANES). Al K-edge XANES of hydrated H-USY and H-ZSM-5 showed evidence for both tetrahedrally and octahedrally coordinated Al and EXAFS data indicated that the Al-O bond distance for tetrahedrally coordinated Al in dehydrated USY and ZSM-5 as 1.67 Angstrom.

A study done on the electronic structures of crystalline and aqueous solutions of LiBr, NaBr, KBr, and KBrO3 using in-situ Br L-edge near edge X-ray absorption fine structure (NEXAFS) under ambient conditions is reported. Discrete variational-X(alpha) (DV-X(alpha)) molecular-orbital calculations are carried out for the Br L3-edge NEXAFS of crystalline KBr and aqueous solution.

X-ray absorption spectroscopy was used to study the structural properties of As-Se-S glass system.

A study investigates disorder in Gd2[Ti(sub1-y)Zr(sub y)](sub 2)O(sub 7) pyrochlores, for y = 0.0-1.0, by Ti 2p and O 1s near-edge X-ray absorption fine structure spectroscopy. Ti(super 4+) ions are found to occupy octahedral sites in Gd2Ti2O7 with a tetragonal distortion induced by vacant oxygen sites.

Depth profiling of sucrose thin films was investigated with time-of-flight secondary ion mass spectrometly (TOP-SIMS) using 10 keV C60+ 20 keV C602+, and 30 keV C603+, and 250, 500, and 1000 eV Cs+ and O2+ as sputtering ions. With C60n+ ions, the molecular ion signal initially decreases and reaches a steady state that is about 38-51% of its original intensity, depending on the energy of the ions. In contrast, with Cs+ and O2+ sputtering, molecular ion signals decrease quickly to the noise level, even using very low-energy (250 eV) ions. In addition, the measured width of the sucrose/Si interface is much narrower using Co ions than that using Cs+ or O2+ ions. To understand the mechanisms of sputtering-induced damage by these ions, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to characterize the bottoms of these sputter craters. XPS data show very little chemical change in the C60+ sputter crater, while considerable amorphous carbon was found in the O2+ and Cs+ sputter craters, indicating extensive decomposition of the sucrose molecules. AFM images show a very flat bottom in the C60+ sputter crater, while the bottoms of the Cs+ and O2+ sputter craters are significantly rougher. We used the sputtering model developed by Wucher and co-workers to quantitatively analyze our C601-3+ data. The results show that low energy C60+, ions generate a relatively thin damage layer with a high molecular ion signal, suggesting that low energy C60+ may be the optimal choice for molecular depth profiling of sucrose films. [ABSTRACT FROM AUTHOR]

Abstract: MTiO3 (M=Fe, Mn, Ni) compounds have received recent attention as possible candidates for multiferroic materials capable of magnetization switching by application of an electric field. In an attempt to stabilize NiTiO3 in the rhombohedral R3 structure, epitaxial Ni1−xTi1−yO3 films of different thickness and composition were deposited on Al2O3(0001) by pulsed laser deposition, and characterized using several techniques. Structural parameters for ilmenite-type NiTiO3 and the metastable LiNbO3-type NiTiO3 structure with the space group R3c were predicted using density functional theory calculations, and compared with the experimental results. Our structural data from X-ray diffraction and X-ray absorption spectroscopy indicate that epitaxial ilmenite-type NiTiO3 films were grown. Furthermore, lattice strain exerted by the sapphire substrate results in a distorted ilmenite structure similar to the LiNbO3-type one. While R3c NiTiO3, the desired structure based on recent theory, cannot be claimed at this point, our results demonstrate the potential of oxide heteroepitaxy to stabilize metastable multiferroic phases that may be difficult to prepare or are inaccessible in the bulk. [Copyright &y& Elsevier]

Abstract: Technetium-99 (Tc) is an important fission product contaminant associated with sites of nuclear fuels reprocessing and geologic nuclear waste disposal. Tc is highly mobile in its most oxidized state and less mobile in the reduced form [Tc(IV)O2·nH2O]. Here we investigate the potential for oxidation of Tc(IV) that was heterogeneously reduced by reaction with biogenic Fe(II) in two sediments differing in mineralogy and aggregation state; unconsolidated Pliocene-age fluvial sediment from the upper Ringold (RG) Formation at the Hanford Site and a clay-rich saprolite from the Field Research Center (FRC) background site on the Oak Ridge Site. Both sediments contained Fe(III) and Mn(III/IV) as redox active phases, but FRC also contained mass-dominant Fe–phyllosilicates of different types. Shewanella putrefaciens CN32 reduced Mn(III/IV) oxides and generated Fe(II) that was reactive with Tc(VII) in heat-killed, bioreduced sediment. After bioreduction and heat-killing, biogenic Fe(II) in the FRC exceeded that in RG by a factor of two. More rapid reduction rates were observed in the RG that had lower biogenic Fe(II), and less particle aggregation. EXAFS measurements indicated that the primary reduction product was a TcO2-like phase in both sediments. The biogenic redox product Tc(IV) oxidized rapidly and completely in RG when contacted with air. Oxidation, in contrast, was slow and incomplete in the FRC, in spite of similar molecular scale speciation of Tc compared to RG. X-ray microprobe, electron microprobe, X-ray absorption spectroscopy, and micro X-ray diffraction were applied to the whole sediment and isolated Tc-containing particles. These analyses revealed that non-oxidizable Tc(IV) in the FRC existed as complexes with octahedral Fe(III) within intra-grain domains of 50–100μm-sized, Fe-containing micas presumptively identified as celadonite. The markedly slower oxidation rates in FRC as compared to RG were attributed to mass-transfer-limited migration of O2 into intra-aggregate and intraparticle domains where Tc(IV) existed; and the formation of unique, oxidation-resistant, intragrain Tc(IV)–Fe(III) molecular species. [Copyright &y& Elsevier]