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Biocellulose or bacterial cellulose (BC) is a biocompatible (nano) material produced with a threedimensional network structure composed of microfibrils having nanometric diameters obtained by the Gluconacetobacter xylinus bacteria. BC membranes present relatively high porosity, allowing the incorporation or synthesis in situ of inorganic nanoparticles for multifunctional applications and have been used as flexible membranes for incorporation of magnetic nanocomposite. In this work, highly stable superparamagnetic iron oxide nanoparticles (SPION), functionalized with polyethylene glycol (PEG), with an average diameter of 5 nm and a saturation magnetization of 41 emu/g at 300K were prepared. PEG-Fe2O3 hybrid was dispersed by mixing a pristine BC membrane in a stable aqueous dispersion of PEG-SPION. The PEG chains at PEG-SPION's surface provide a good permeability and strong affinity between the BC chains and SPION through hydrogen-bonding interactions. PEG-SPION also allow the incorporation of higher content of nanoparticles without compromising the mechanical properties of the nanocomposite. Structural and magnetic properties of the composite have been characterized by XRD, SEM, energy-dispersive X-ray spectroscopy (EDX), magnetization, Raman spectroscopy, and magnetic force microscopy. [ABSTRACT FROM AUTHOR]

Experimental mechanistic studies of iridium-catalyzed, enantioselective allylic substitution enabled by (phosphoramidite,olefin) ligands are reported. (η2-Allylic alcohol)iridium(I) and (η3-allyl)iridium(III) complexes were synthesized and characterized by NMR spectroscopy as well as X-ray crystallography. The substrate complexes are catalytically and kinetically competent to be intermediates in allylic substitutions of branched, racemic allylic alcohols with various nucleophiles. In addition, we have identified an off-cycle pathway involving reversible binding of molecular oxygen to iridium, which contributes to the air tolerance of the catalyst system. [ABSTRACT FROM AUTHOR]

N-F-co-embedded titania (N-F-TiO2) photocatalysts with varying N:F ratios were synthesized and tested for their ability to photocatalyze the degradation of pollutants present at indoor air levels using visible light. The synthesis was achieved using a solvothermal process with tetrabutyl titanate, urea and ammonium fluoride as sources of Ti, N and F, respectively. Three selected volatile organic compounds (toluene, ethyl benzene and o-xylene) were selected as the test pollutants. The prepared composites were characterized using X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and Ultra-violet (UV)-visible spectroscopy. The photocatalytic degradation efficiencies of N-F-TiO2 composites were higher than those obtained using pure TiO2 and N-TiO2. Moreover, these efficiencies increased as the N:F ratio decreased from sixteen to eight, then decreased as it dropped further to three, indicating the presence of an optimal N:F ratio. Meanwhile, as retention time decreased from 12.4 to 0.62 s, the average photocatalytic efficiencies decreased from 65.4% to 21.7%, 91.5% to 37.8% and 95.8% to 44.7% for toluene, ethyl benzene and o-xylene, respectively. In contrast, the photocatalytic reaction rates increased as retention time decreased. In consideration of all of these factors, under optimized operational conditions, the prepared N-F-TiO2 composites could be utilized for the degradation of target pollutants at indoor air levels using visible light. [ABSTRACT FROM AUTHOR]

The optical design of a two-dimensional imaging soft X-ray spectrometer is described. A monochromator will produce a dispersed spectrum in a narrow vertical illuminated stripe (~2 mm wide by ~2 mm tall) on a sample. The spectrometer will use inelastically scattered X-rays to image the extended field on the sample in the incident photon energy direction (vertical), resolving the incident photon energy. At the same time it will image and disperse the scattered photons in the orthogonal (horizontal) direction, resolving the scattered photon energy. The principal challenge is to design a system that images from the flat-field illumination of the sample to the flat field of the detector and to achieve sufficiently high spectral resolution. This spectrometer provides a completely parallel resonant inelastic X-ray scattering measurement at high spectral resolution (~30000) over the energy bandwidth (~5 eV) of a soft X-ray absorption resonance. [ABSTRACT FROM AUTHOR]

We investigate the possibility of constructing a unified model for the radio and X-ray outbursts of nova CI Cam 1998 in terms of the shock interaction of the nova envelope with circumstellar gas. In a spherical model, we manage to describe the kinematics and evolution of the radio source flux and very roughly the evolution of the X-ray flux. The X-ray spectrum in this model is appreciably harder. Better agreement with observations in all respects is shown by the model for the interaction of a spherical nova envelope with a nonspherical circumstellar medium. The latter is simulated in our model by a combination of rarefied bipolar conical outflows of stationary wind with an opening angle of 120° and a dense equatorial disk. In the optimal model, the initial kinetic energy of the nova envelope is ∼5 × 1043 erg and its mass lies within the range (1–5) × 10−7 M⊙. The energy and mass of the nova envelope as well as the mass loss rate in the nonspherical model are close to those obtained in the spherical model by Filippova et al. (2008). [ABSTRACT FROM AUTHOR]

An improved high luminosity, easily spectrally tunable backlighting scheme based on a spherically bent crystal is considered in this paper. Contrary to the traditional backlighting scheme, we used crystal far from normal incidence, and the backlighter source was inside the Rowland circle. With the presented configuration, we obtained a spatial resolution up to 8 mm in the desired direction with an X-ray backlighting energy close to 5 keV. Detailed discussions and ray-tracing calculations show that with this convenient scheme resolution down to 5 mm can be achieved. A dedicated application to high energy density physics is presented: the radiography of shock compressed matter. [ABSTRACT FROM AUTHOR]

In this work, the general purpose Monte Carlo N-particle radiation transport computer code (MCNP-4C) was used for the simulation of X-ray spectra in diagnostic radiology. The electron's path in the target was followed until its energy was reduced to 10 keV. A user-friendly interface named 'diagnostic X-ray spectra by Monte Carlo simulation (DXRaySMCS)' was developed to facilitate the application of MCNP-4C code for diagnostic radiology spectrum prediction. The program provides a user-friendly interface for: (i) modifying the MCNP input file, (ii) launching the MCNP program to simulate electron and photon transport and (iii) processing the MCNP output file to yield a summary of the results (relative photon number per energy bin). In this article, the development and characteristics of DXRaySMCS are outlined. As part of the validation process, output spectra for 46 diagnostic radiology system settings produced by DXRaySMCS were compared with the corresponding IPEM78. Generally, there is a good agreement between the two sets of spectra. No statistically significant differences have been observed between IPEM78 reported spectra and the simulated spectra generated in this study. [ABSTRACT FROM AUTHOR]

Abstract: KLM Auger spectra of Ni metal were measured with high energy resolution and high statistical accuracy using monochromatic synchrotron radiation. The spectra were corrected for the background from inelastically scattered electrons using partial intensity analysis where the electron trajectories were calculated by Monte Carlo simulation. Following background correction, the corrected spectra were fitted to model peaks taking into account intrinsic excitations. The measured transition energy of the most intense KL2M3 (1D2) Auger line is 7388.1eV (0.4). The obtained relative intensities and energies of the Auger diagram lines are compared to published calculations as well as to experimental data for other 3d transition metals. In addition, the presence of Ni 3s, 3p photoelectron peaks in the spectra excited internally by Ni Kα X-rays is shown. [Copyright &y& Elsevier]

In March 2005 a superconducting cold-bore undulator was installed in ANKA (ANSTROEM SOURCE IN KARLSRUHE) and since that time has been in operation. The purpose of the installation was to evaluate if such a device can be operated in a heavy duty synchrotron radiation user facility like ANKA without problems. In order to demonstrate this the generated spectra were measured and the heat load induced by the beam was investigated. It was shown that the heat deposited by the beam in the 8 mm gap is less than 1 W per 100 mA at 2.5 GeV and can be cooled by cryocoolers. Finally, reference is made to the spectra produced by sub-picosecond X-rays using a special ANKA optics. [ABSTRACT FROM AUTHOR]

The variation in reconstruction in the InSb (111)In surface during adsorption of sulfur and annealing in ultrahigh vacuum was investigated by methods of low-energy electron diffraction and Auger electron spectroscopy. It is shown that evolution of reconstruction of the InSb (111)In surface substantially depends on the starting thickness of the adsorbed S layer on the surface. If the thickness of the S layer is only slightly larger than that of the monolayer, reconstruction (1 × 1) is formed on the surface, which transforms into reconstruction (2 × 2) during the subsequent annealing. If the S layer is several monolayers thick, this layer is initially amorphous. Annealing of such a surface at 315–325°C can lead to the formation of reconstruction (√3 × √3)- R30°, which transforms into reconstruction (2 × 2) at a higher temperature. This reconstruction is retained during further annealing until the S atoms vanish from the surface completely. It is shown for the first time that the reconstruction (√3 × √3)- R30° can form during adsorption of chalcogenide atoms on the III–V (111)III surface. [ABSTRACT FROM AUTHOR]

All the confirmed Soft Gamma-ray Repeaters have been observed with the EPIC instrument on the XMM–Newton satellite. We review the results obtained in these observations, providing the most accurate spectra on the persistent X-ray emission in the 1–10 keV range for these objects, and discuss them in the context of the magnetar interpretation. [ABSTRACT FROM AUTHOR]

A bent-crystal Laue {or Cauchois [J. Phys. Radium 3, 320 (1932)] geometry} spectrograph is a good compromise between sensitivity and spectral resolution for measuring x-ray spectra (15

We examine the prospects for studying the pre-reionization intergalactic medium (IGM) through the so-called 21-cm forest in spectra of bright high-redshift radio sources. We first compute the evolution of the mean optical depth τ for models that include X-ray heating of the IGM gas, Wouthuysen–Field coupling, and reionization. Under most circumstances, the spin temperature TS grows large well before reionization begins in earnest; this occurs so long as the X-ray luminosity of high-redshift starbursts (per unit star formation rate) is comparable to that in nearby galaxies. As a result, throughout most of reionization, and background sources must sit well beyond the reionization surface in order to experience absorption that is measurable by square-kilometre class telescopes. H ii regions produce relatively large ‘transmission gaps’ and may therefore still be observable during the early stages of reionization. Absorption from sheets and filaments in the cosmic web fades once TS becomes large and should be rare during reionization. Minihaloes can produce strong (albeit narrow) absorption features. Measuring their abundance would yield useful limits on the strength of feedback processes in the IGM as well as their effect on reionization. [ABSTRACT FROM AUTHOR]

We have studied the face-on, barred spiral NGC 7424 (site of the rare Type IIb SN 2001ig) with Chandra, Gemini and the Australia Telescope Compact Array. After giving revised X-ray colours and luminosity of the supernova, here we focus on some other interesting sources in the galaxy: in particular, our serendipitous discovery of two ultraluminous X-ray sources (ULXs). The brighter one has a power-law-like spectrum with photon index . The other ULX shows a spectral state transition or outburst between the two Chandra observations, 20-d apart. Optical data show that this ULX is located in a young (age ≈7–10 Myr), bright complex rich with OB stars and clusters. An exceptionally bright, unresolved radio source (0.14 mJy at 4.79 GHz, implying a radio luminosity twice as high as Cas A) is found slightly offset from the ULX (≈80 pc). Its radio spectral index suggests optically thin synchrotron emission, either from a young supernova remnant or from a radio lobe powered by a ULX jet. An even brighter, unresolved radio source (0.22 mJy at 4.79 GHz) is found in another young, massive stellar complex, not associated with any X-ray sources: based on its flatter radio spectral index , we suggest that it is a young pulsar wind nebula, a factor of 10 more radio luminous than the Crab. [ABSTRACT FROM AUTHOR]

We discuss the expected X-ray spectral and variability properties of black hole accretion discs at high luminosity, under the hypothesis that radiation-pressure-dominated discs are subject to violent clumping instabilities and, as a result, have a highly inhomogeneous two-phase structure. After deriving the full accretion disc solutions explicitly in terms of the parameters of the model, we study their radiative properties both with a simple two-zone model, treatable analytically, and with radiative transfer simulations which account simultaneously for energy balance and Comptonization in the hot phase, together with reflection, reprocessing, ionization and thermal balance in the cold phase. We show that, if not only the density, but also the heating rate within these flows is inhomogeneous, then complex reflection-dominated spectra can be obtained for a high enough covering fraction of the cold phase. In general, large reflection components in the observed X-ray spectra should be associated with strong soft excesses, resulting from the combined emission of ionized atomic emission lines. The variability properties of such systems are such that, even when contributing to a large fraction of the hard X-ray spectrum, the reflection component is less variable than the power-law-like emission originating from the hot Comptonizing phase, in agreement with what is observed in many Narrow Line Seyfert 1 galaxies and bright Seyfert 1. Our model falls within the family of those trying to explain the complex X-ray spectra of bright AGN with ionized reflection, but presents an alternative, specific, physically motivated, geometrical set-up for the complex multiphase structure of the inner regions of near-Eddington accretion flows. [ABSTRACT FROM AUTHOR]

We have newly developed an x-ray photoemission electron microscope (XPEEM) which uses both soft x-rays and hard x-rays at the undulator beam line BL15XU in the synchrotron radiation (SR) facility SPring-8 to observe various practical materials. In combination with an energy analyzer and high brilliant x-ray source, the detection of high kinetic energy inner-shell photoelectrons is essential for revealing the chemical properties of specimen subsurfaces or buried interfaces, owing to long inelastic mean free path of the high kinetic energy photoelectrons. The most significant result in our design is the new combined electric and magnetic field objective lens in which the magnetic field penetrates up to the sample surface. This allows the measurement with high spatial resolution of both low intensity images of inner-shell photoelectrons with high kinetic energy and high intensity images of secondary electrons. By using the sample bias scan method, we can easily change the focus condition of the objective lens in order to allow the energy filtered imaging with photoelectrons having the kinetic energy in a wide range (1–10 000 eV). By the combination of high brilliant SR x-rays, the new objective lens, and sample bias method, our XPEEM can successfully obtain the microarea x-ray photoelectron spectra and energy filtered XPEEM images of inner-shell photoelectrons, such as Si 1s, without any surface cleaning procedure. The energy filtered XPEEM image using photoelectrons from deep inner shells, Si 1s, was obtained for the first time. [ABSTRACT FROM AUTHOR]

Progress in third-generation synchrotron radiation facilities has made possible, nowadays, the determination of induced spin and orbital magnetic moments of 5d transition metal elements via the element-specific X-ray magnetic circular dichroism technique. In this work, recent results on the magnetic moments of Pt in Co-based alloys and multilayers are briefly reviewed. The magnetic moment carried by the 5d electrons of Pt in these systems ranges between 0.2 and 0.7μB/atom. The ratio of orbital μL to spin μS magnetic moment is found to be in the range 0.15–0.25. Finally, a method is described for the determination of Pt magnetic moment in lattices other than the fcc lattice, which is the thermodynamically stable crystallographic structure of bulk Pt. [ABSTRACT FROM AUTHOR]

A simple computational method is proposed for estimating the time-dependent flux F[ΔE](t) of an x-ray spectrum S(E,t) over domain [ΔE] from data Dk(t)(k=1,...,N) obtained by an N-channel array of filtered detectors. It is assumed that the data are related to the spectrum by a discrete, inhomogeneous, first-kind Fredholm integral equation Dk=∫S(E,t)Rk(E)dE, where Rk(E) is the known response function for each detector channel of the diagnostic. The proposed method constructs a spectral sensitivity HLS(E) for the diagnostic array as a linear combination ∑k=1NakRk(E) of the responses, where the coefficients ak are obtained by a least-squares criterion plus a constraint. The ak values, once determined, apply as long as the responses are valid. The flux estimate is then simply FLS(t)=∑k=1NakDk(t), without a spectral unfold of the data. The method is useful for quick analyses of time-dependent data, for comparisons with other flux-measuring diagnostics, and for the experimental design of filtered-detector arrays. The method is applied to a five-channel array of filtered photoemissive x-ray detectors [G. A. Chandler et al., Rev. Sci. Instrum. 70, 561 (1999)], used for z-pinch measurements at the Z-accelerator facility [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)]. Comparisons with unfold results are made, and a first-order analysis of error propagation into FLS(t) is presented. [ABSTRACT FROM AUTHOR]

‘Long’ γ-ray bursts (GRBs) are commonly accepted to originate in the explosion of particularly massive stars, which give rise to highly relativistic jets. Inhomogeneities in the expanding flow result in internal shock waves that are believed to produce the γ-rays we see. As the jet travels further outward into the surrounding circumstellar medium, ‘external’ shocks create the afterglow emission seen in the X-ray, optical and radio bands. Here we report observations of the early phases of the X-ray emission of five GRBs. Their X-ray light curves are characterised by a surprisingly rapid fall-off for the first few hundred seconds, followed by a less rapid decline lasting several hours. This steep decline, together with detailed spectral properties of two particular bursts, shows that violent shock interactions take place in the early jet outflows. [ABSTRACT FROM AUTHOR]

The formation of a volume discharge in an open gas diode with coaxial electrodes was accompanied by hard X-ray emission. The conditions of supershort avalanche electron beam formation are retained at a pulse repetition rate up to 1.5 kHz. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Many inorganic species are now recognized as being essential for life, including many forms of sulfur, phosphate and numerous classes of metal ions. For example, recent progress in the fields of biochemistry and biology has pointed out the critical importance of sulfur in the biosynthesis of vital cofactors and active sites in proteins, and in the complex reaction mechanisms often involved. Special attention has also been drawn to the diverse roles of alkaline (Na+, K+) and alkaline earth (Mg2+, Ca2+) metal ions in mediating the activity of RNA, proteins and many processes in living cells. While the general effect of these ions in biology is mostly understood, information on their detailed role is deficient. Here the application of softer X-ray absorption spectroscopy (XAS) to probe the local structural and electronic environment of such ions within their biological complexes and during physiological reactions is discussed. In addition, the required experimental set-up and the difficulties associated with conducting softer XAS experiments on biological samples are presented. [ABSTRACT FROM AUTHOR]

Abstract: The article presents an analytical model to simulate experimental imperfections in the realization of an X-ray absorption spectroscopy experiment, performed in transmission or fluorescence mode. Distinction is made between sources of systematic errors on a time-scale basis, to select the more appropriate model for their handling. For short time-scale, statistical models are the most suited. For large time-scale, the model is developed for sample and beam imperfections: mainly sample inhomogeneity, sample self-absorption, beam achromaticity. The ability of this model to reproduce the effects of these imperfections is exemplified, and the model is validated on real samples. Various potential application fields of the model are then presented. [Copyright &y& Elsevier]

Abstract: The mechanical properties like hardness and reduced modulus of Si-, SiO x - and SiN x -containing a-C:H films (denoted as DLCSi, DLCSiO and DLCSiN), deposited respectively from tetramethylsilane, hexamethyldisiloxane and hexamethyldisilazane precursors onto silicon wafer by electron cyclotron wave resonance (ECWR) RF plasma beam CVD, have been determined by nanoindentation method. Relationships have been established between the nanomechanical properties and the self-bias developed during deposition, as well as the chemical structural parameters determined previously by X-ray photoelectron spectroscopy and X-ray induced Auger electron spectroscopy. In particular, an increase of the self-bias up to about 200 V during deposition led to a significant increase in the hardness of the layers. The hardness had a tendency to decrease with increasing O-content, and to increase with the increase of the modified Auger parameter for Si. The latter was attributed to the increase in the degree of crosslinking. For the first time, the hardness was found to increase with the increase of the bulk plasmon loss energy of the C 1s peak, which was interpreted in terms of the increase in the mass density. [Copyright &y& Elsevier]

Superconducting tunnel junction (STJ) X-ray spectrometers have been developed for high-resolution soft X-ray spectroscopy. We are quantifying the improvement in sensitivity and signal-to-noise ratio that STJ spectrometers can offer for the analysis of dilute specimens over conventional semi-conductor and grating spectrometers. We present analytical equations to quantify the improvement in terms of spectrometer resolution, detection efficiency and count rate capabilities as a function of line separation and spectral background. We discuss the implications of this analysis for L-edge spectroscopy of first-row transition metals. [ABSTRACT FROM AUTHOR]

X-ray magnetic circular dichroism in absorption of the single-crystal iron layer deposited epitaxially on MgO substrate is studied. Spin and orbital moment, 0.069 and 2.33 μB, respectively, are calculated in terms of the XMCD sum rules. Our results are accordant to those published. Experiments show that the orbital moment would be decreased to that in bulk materials as iron film is thinned down, but spin moment changes little. [ABSTRACT FROM AUTHOR]

Abstract: We made a detailed study of the impulsive solar flare of GOES class X1.0 which occurred near the west limb on 2002 August 3, peak time 19:07UT. There is particularly good data coverage of this event, with simultaneous observations in EUV, soft and hard X-rays available. We used TRACE 171Å images to study the morphology and evolution of this event. Soft X-ray spectra in the wavelength range 3.34–6.05Å measured by the RESIK Bragg crystal spectrometer on CORONAS-F were used for determination of the evolution of the flare plasma temperature. Data from the RHESSI instrument were used to investigate properties of the higher-temperature plasma during the flare. [Copyright &y& Elsevier]

At the High Energy Beamline ID15A at the European Synchrotron Radiation Facility we have developed a fast three-dimensional x-ray microtomography system, which acquires a complete dataset in typically less than 10 s. This unprecedented speed is achieved by combining a high efficiency phosphor screen, a reflecting microscope objective and a fast charge coupled device detector with the very intense high-energy white beam radiation provided by a wiggler source. The achieved spatial resolution is 2 μm. The available x-ray energy spectrum spans from 20 to 250 keV and can therefore be used for low and high Z materials. The spectrum can be modified by inserting different filters into the x-ray beam in order to optimize the signal-to-noise ratio and to avoid beam-hardening artifacts. Different phosphors with different energy sensitivity can be used. The very high speed allows in situ studies of systems evolving on the time scale of a few seconds or minutes. Three examples are given on sintering of metallic powders, solidification of binary alloys and liquid front propagation in granular materials. [ABSTRACT FROM AUTHOR]

Probing the structure of materialsin situis of central importance in heterogeneous catalysis. Mostly, this is done in an integral manner, that is without spatial resolution. However, at high conversion in a catalyst bed prominent concentration and/or temperature profiles may exist which can result in significant spatial variation of the catalyst structure. In the present study, X-ray absorption spectroscopy combined with on-line mass spectrometry was used to monitor the structural changes of a Pt-Rh/Al2O3 catalyst in a fixed-bed reactor during partial oxidation of methane. The reaction ignited at 310 °C and integral X-ray absorption spectroscopy showed that the Rh-Pt-particles were reduced at the same time. However, monitoring with a beam of 1 mm × 0.6 mm size along the axial position of the catalyst bed uncovered that Rh and Pt were still in oxidized state in the entrance region, whereas they were in reduced state in the zone at the end of the catalyst bed. The gradual transition from the reduced to the oxidized state was found to shift towards the bed entrance if the temperature was slightly increased. [ABSTRACT FROM AUTHOR]

Gold nanoparticles were supported on Al2O3 by a deposition-precipitation method followed by heating in He. The resulting catalyst was then treated with NaCN solutions to remove most of the gold. X-ray absorption spectroscopy at the Au LIII edge was used to monitor the oxidation state and atomic structure of Au throughout the procedure. The gold or a Au/Al2O3 sample after deposition-precipitation was in a +3 oxidation state and was subsequently reduced to metal after heating to 623 K in He. Treatment of a reduced sample with either 1 or 2 wt. % NaCN in water removed 79% or 86% of the Au, respectively. Although the remaining Au was cationic, it was also reduced to metal after heating to 623 K in He. The rate of CO oxidation per gold atom, the apparent activation energy, and the orders of reaction were unaffected by the NaCN treatments. These results show that alumina does not stabilize cationic Au species and that metallic Au appears to be important for the CO oxidation reaction. The presence of water or H2 increased the rate of CO oxidation over all of the Au/Al2O3 catalysts. However, the promotional effect of co-fed water was greater over the NaCN treated samples. [ABSTRACT FROM AUTHOR]

Abstract: Grazing incidence X-rays diffraction (GI-XRD), X-rays reflectivity (XRR) and positron annihilation spectroscopy (PAS) analysis on Pd–Mg thin bilayer films deposited by electron-gun on Si wafer and glass substrate evidence a two-region structure: (i) a surface region consisting of the Pd capping layer, the Mg–Pd interface and some Mg subinterface layers; because of the interface roughness, in this region the deposited Mg layers are encased in Pd and, upon the metal to deuteride phase transition, they became highly compressed by the Pd capping layer; (ii) a second region consisting of a pure Mg layer, which extends up to the substrate. This two-region structure is stable upon repeated D2 absorption and desorption cycles. PAS analysis reveals the formation of vacancy-like defects after D2 desorption at a concentration higher than that of the as-deposited sample. The two-region structure and the defect dynamics observed in the present study can explain the presence of two peaks in the deuterium desorption spectrum and the diminished D2 storage efficiency after the first D2 absorption and desorption cycles. [Copyright &y& Elsevier]

Cerium-modified Bi4Ti3O12 thin films were deposited on GaN substrates by the pulsed laser deposition method. The substrate temperature was varied from 600°C to 750°C in 50°C steps. The surface topographies and orientations of the Bi0.4Ce0.6Ti3O12 (BCeT) films were gradually changed in proportion to the substrate temperature. The diffusion reaction between BCeT and the GaN layer and the depth profiles of the films were investigated by Auger electron spectroscopy (AES), The ferroelectric properties and leakage current characteristics of the metal-ferroelectric-GaN stacked thin films were measured and discussed. [ABSTRACT FROM AUTHOR]

Abstract We have used potentiodynamic polarization curves and Auger electron spectroscopy to determine the characteristic features of the anodic and cathodic behavior in a 0.5 M H2SO4 solution of sintered nonporous samples of polycrystalline a-SiC. We have shown that anodic oxidation of silicon carbide first leads to formation of a surface layer of a solid solution of oxygen in a-SiC, and then a layer of a metastable oxycarbide phase SiC0.67O0.33. We have established that during cathodic polarization, the process of evolution of hydrogen first occurs according to a slow discharge mechanism, and for more extensive polarization it occurs according to a mechanism of surface recombination of atoms. [ABSTRACT FROM AUTHOR]

X-ray absorption spectroscopy (XAS) in the intermediate x-ray region (2–6 keV) for dilute biological samples has been limited because of detector/flux limitations and inadequate cryogenic instrumentation. We have designed and constructed a new tailpiece/sample chamber for a commercially available liquid helium cooled cryostat which overcomes difficulties related to low fluorescence signals by using thin window materials and incorporating an internal photodiode detector. With the apparatus, XAS data at the Cl, S, and Ca K edges have been collected on frozen solutions and biological samples at temperatures down to 60 K. A separate chamber has been incorporated for collecting room-temperature spectra of standard compounds (for energy calibration purposes) which prevents contamination of the cryostat chamber and allows the sample to remain undisturbed, both important concerns for studying dilute and radiation-sensitive samples. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The Canadian Light Source (CLS) in Saskatoon has been under construction for the last 4 years, and will be producing a number of very intense beams of far-IR, IR, soft and hard X-rays in 2004 for use by several hundred Canadian scientists in chemistry, surface and material science, and a host of other scientific disciplines. The CLS will dramatically enhance the Canadian spectroscopic tradition that Gerhard Herzberg help create. I begin this article (from my 2002 CIC Montreal Medal lecture) with an overview of the history of SR in Canada, beginning in 1972 with the first Canadian synchrotron workshop organized at the University of Western Ontario by Bill McGowan, and attended by Dr. Herzberg. The CLS facility is then described, along with the properties of the first and second set of beamlines to be built at the CLS. These SR beams, in the IR and X-ray regions from the third generation CSL ring, will be competitive in brightness and intensity with the best beamlines in the world for most applications. Finally, some of the present Canadian SR research at foreign SR sources is described across the entire SR spectrum. All known spectroscopic and diffraction experiments are dramatically enhanced with SR; and SR opens up new areas of spectroscopy, microscopy, and spectromicroscopy that cannot be studied with any other source of radiation. [ABSTRACT FROM AUTHOR]

Discusses a new method for spectroscopically characterizing buried interfaces using soft X-ray standing waves that permits much more quantitatively analyzing compositions, chemical and magnetic structure and electronic structure. Results of probing buried magnetic interfaces with soft X-ray standing wave spectroscopes; Measurement of rocking curves; Scan and thickness.

Core-hole clock spectroscopy and near-edge x-ray-absorption fine structure measurements have been used to investigate the ultrafast electron transfer dynamics at the Copper(II) phthalocyanine (CuPc)/Au(111) interface. It was found that the strong electronic coupling between the first layer of CuPc molecules and Au(111) substrate favors ultrafast electron transfer from the lowest unoccupied molecular orbital of the CuPc molecules to the conduction band of Au(111) in the time scale of ∼6 fs. In contrast, the intermolecular electron transfer within multilayers of CuPc molecules via the weak van der Waals interaction was much slower. [ABSTRACT FROM AUTHOR]

We report on the 55Fe x-ray pulse height spectrum of an annular superconducting tunnel junction (STJ) collected without an external magnetic field. An energy resolution of 100 eV was obtained for the Kα line of the top electrode. The Josephson critical current and Fiske resonances were suppressed by the presence of trapped magnetic flux quanta which created a persistent current and self-generated magnetic field. The obtained energy resolution and the stability of the trapped magnetic flux under irradiation demonstrate the capability of an annular STJ device with trapped flux quanta to detect radiation without using the external magnetic field that is required in the conventional detection scheme. [ABSTRACT FROM AUTHOR]

The ultrahigh peak brilliance available at X-ray free-electron lasers opens the possibility to transfer nonlinear spectroscopic techniques from the optical and infrared into the X-ray regime. Here, we present a conceptual treatment of nonlinear X-ray processes with an emphasis on stimulated resonant X-ray scattering as well as a quantitative estimate for the scaling of stimulated X-ray scattering cross sections. These considerations provide the order of magnitude for the required X-ray intensities to experimentally observe stimulated resonant X-ray scattering for photon energies ranging from the extreme ultraviolet to the soft and hard X-ray regimes. At the same time, the regime where stimulated processes can safely be ignored is identified. With this basis, we discuss prospects and implications for spectroscopy, scattering, and imaging experiments at X-ray free-electron lasers. [ABSTRACT FROM PUBLISHER]

To investigate the effect of plasma-incorporated fluorine on Si donors in pseudomorphic-high electron mobility transistors (P-HEMTs), we used x-ray photoemission spectroscopy to analyze three layers near the Si ä-doped layer and the Si ä-doped layer itself, in which we previously found fluorine accumulation after post-thermal annealing following fluorocarbon-based plasma exposure. For this evaluation, we developed controllable and low-speed AlGaAs wet-chemical etching using citric-acid-based wet etchant. We used it to expose one of the layers to be analyzed: one 7.5 nm above the Si ä-doped layer, one 1.5 nm above it, the ä-doped layer itself, and one 1.5 nm below it. We found that the accumulated fluorine localized in the ä-doped layer and reacted with Si donors. This is apparently the main reason for the carrier passivation in the fluorocarbon-based plasma-exposed P-HEMTs. [ABSTRACT FROM AUTHOR]