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It appears that As(III) can be oxidized to As(V) while Cu(II) is reduced to Cu(I) and Cu(0). The molecular-scale data are very useful in revealing the oxidation states and interconversions of arsenic during the photocatalytic reactions. This work has implications in that the toxicity of arsenic in contaminated groundwater or wastewater can be effectively decreased via solar-driven photocatalysis, which may facilitate further treatments by coagulation.X-ray absorption is a sensitive and versatile tool for chemical speciation. However, when high doses are used, the absorbed energy can change the composition, amount and structure of the native material, thereby changing the aspects of the absorption process on which speciation is based. How can one calculate the dose when X-ray irradiation affects the chemistry and changes the amount of the material? This paper presents an assumption-free approach which can retrieve from the experimental data all dose-sensitive parameters - absorption coefficients, composition (elemental molecular units), material densities - which can then be used to calculate accurate doses as a function of irradiation. This approach is illustrated using X-ray damage to a solid film of a perfluorosulfonic acid fluoropolymer in a scanning transmission soft X-ray microscope. This new approach is compared against existing dose models which calculate the dose by making simplifying assumptions regarding the material quantity, density and chemistry. While the detailed measurements used in this approach go beyond typical methods to experimental analytical X-ray absorption, they provide a more accurate quantitation of radiation dose, and help to understand mechanisms of radiation damage.Ultra-SAXS can enhance the capabilities of existing synchrotron SAXS/WAXS beamlines. A compact ultra-SAXS module has been developed, which extends the measurable q-range with 0.0015 ≤ q (nm-1) ≤ 0.2, allowing structural dimensions in the range 30 ≤ D (nm) ≤ 4000 to be probed in addition to the range covered by a high-end SAXS/WAXS instrument. By shifting the module components in and out on their respective motor stages, SAXS/WAXS measurements can be easily and rapidly interleaved with USAXS measurements. The use of vertical crystal rotation axes (horizontal diffraction) greatly simplifies the construction, at minimal cost to efficiency. In this paper, the design considerations, realization and synchrotron findings are presented. Measurements of silica spheres, an alumina membrane, and a porous carbon catalyst are provided as application examples.Small-angle X-ray scattering (SAXS) is an established method for studying nanostructured systems and in particular biological macromolecules in solution. To obtain element-specific information about the sample, anomalous SAXS (ASAXS) exploits changes of the scattering properties of selected atoms when the energy of the incident X-rays is close to the binding energy of their electrons. While ASAXS is widely applied to condensed matter and inorganic systems, its use for biological macromolecules is challenging because of the weak anomalous effect. Biological objects are often only available in small quantities and are prone to radiation damage, which makes biological ASAXS measurements very challenging. The BioSAXS beamline P12 operated by the European Molecular Biology Laboratory (EMBL) at the PETRA III storage ring (DESY, Hamburg) is dedicated to studies of weakly scattering objects. Here, recent developments at P12 allowing for ASAXS measurements are presented. The beamline control, data acquisition and data reduction pipeline of the beamline were adapted to conduct ASAXS experiments. Modelling tools were developed to compute ASAXS patterns from atomic models, which can be used to analyze the data and to help designing appropriate data collection strategies. These developments are illustrated with ASAXS experiments on different model systems performed at the P12 beamline.Several different ways of measuring the energy resolution for meV-resolved inelastic X-ray scattering (IXS) are compared using scattering from poly(methyl methacrylate), PMMA, using scattering from borosilicate glass (Tempax), and using powder diffraction from aluminium. All of these methods provide a reasonable first approximation to the energy resolution, but, also, in all cases, inelastic contributions appear over some range of energy transfers. Over a range of ±15 meV energy transfer there is good agreement between the measurements of PMMA and Tempax at low temperature, and room-temperature powder diffraction from aluminium, so we consider this to be a good indication of the true resolution of our ∼1.3 meV spectrometer. The resolution over a wider energy range is self-consistently determined using the temperature, momentum and sample dependence of the measured response. The inelastic contributions from the PMMA and Tempax, and their dependence on momentum transfer and temperature, are then quantitatively investigated. The resulting data allow us to determine the resolution of our multi-analyzer array efficiently using a single scan. The importance of this procedure is demonstrated by showing that the results of the analysis of a spectrum from a glass are changed by using the properly deconvolved resolution function. The impact of radiation damage on the scattering from PMMA and Tempax is also discussed.The widespread use and development of inertia friction welding is currently restricted by an incomplete understanding of the deformation mechanisms and microstructure evolution during the process. Understanding phase transformations and lattice strains during inertia friction welding is essential for the development of robust numerical models capable of determining optimized process parameters and reducing the requirement for costly experimental trials. A unique compact rig has been designed and used in-situ with a high-speed synchrotron X-ray diffraction instrument to investigate the microstructure evolution during inertia friction welding of a high-carbon steel (BS1407). At the contact interface, the transformation from ferrite to austenite was captured in great detail, allowing for analysis of the phase fractions during the process. Measurement of the thermal response of the weld reveals that the transformation to austenite occurs 230 °C below the equilibrium start temperature of 725 °C. It is concluded that the localization of large strains around the contact interface produced as the specimens deform assists this non-equilibrium phase transformation.Synchrotron radiation can induce sample damage, whether intended or not. In the case of sensitive samples, such as biological ones, modifications can be significant. To understand and predict the effects due to exposure, it is necessary to know the ionizing radiation dose deposited in the sample. In the case of aqueous samples, deleterious effects are mostly induced by the production of reactive oxygen species via water radiolysis. These species are therefore good indicators of the dose. Here the application of a microfluidic cell specifically optimized for low penetrating soft X-ray radiation is reported. selleckchem Sodium benzoate was used as a fluorescent dosimeter thanks to its specific detection of hydroxyl radicals, a radiolytic product of water. Measurements at 1.28 keV led to the determination of a hydroxyl production yield, G(HO.), of 0.025 ± 0.004 µmol J-1. This result is in agreement with the literature and confirms the high linear energy transfer behavior of soft X-rays. An analysis of the important parameters of the microfluidic dosimetry cell, as well as their influences over dosimetry, is also reported.A scheme to generate wide-bandwidth radiation using a step-wise tapered undulator with a segmented structure is proposed. This magnetic field configuration allows to broaden the undulator harmonic spectrum by two orders of magnitude, providing 1 keV bandwidth with spectral flux density exceeding 1016 photons s-1 mm-2 (0.1% bandwidth)-1 at 5 keV on the sample. Such a magnetic setup is applicable to superconducting devices where magnetic tapering cannot be arranged mechanically. The resulting radiation with broadband spectrum and flat-top shape may be exploited at a multipurpose beamline for scanning over the spectrum at time scales of 10-100 ms. The radiation from a segmented undulator is described analytically and derivations with numerical simulations are verified. In addition, a start-to-end simulation of an optical beamline is performed and issues related to the longitudinally distributed radiation source and its image upon focusing on the sample are addressed.The detailed fabrication and performance of the temperature-gradient analyzers that were simulated by Ishikawa & Baron [(2010). J. Synchrotron Rad. 17, 12-24] are described and extended to include both quadratic and 2D gradients. The application of a temperature gradient compensates for geometric contributions to the energy resolution while allowing collection of a large solid angle, ∼50 mrad × 50 mrad, of scattered radiation. In particular, when operating relatively close to backscattering, π/2 - θB = 1.58 mrad, the application of a gradient of 1.32 K per 80 mm improves the measured total resolution from 60 to 25 meV at the full width at half-maximum, while when operating further from backscattering, π/2 - θB = 6.56 mrad, improvement from 330 to 32 meV is observed using a combination of a gradient of 6.2 K per 80 mm and dispersion compensation with a position-sensitive detector. In both cases, the operating energy was 15.8 keV and the incident bandwidth was 22 meV. Notably, the use of a temperature gradient allows a relatively large clearance at the sample, permitting installation of more complicated sample environments.A mathematical apparatus for solving problems of X-ray wave propagation through complex optical systems, when the lens thickness can change with jumps, is developed and presented. The developed method is based on the use of the superposition of oriented Gaussian beams, which satisfy the Helmholtz equation with high accuracy. The wave propagation in air and through kinoform and ordinary lenses is considered. Focusing and imaging properties are compared for both types of X-ray optics. The diffraction effects arising due to thickness jumps in the kinoform lenses and the influence of these jumps on the X-ray focusing and imaging are investigated. The prospect of using the developed theory for X-ray optics applications is discussed.Owing to the development of X-ray focusing optics during the past decades, synchrotron-based X-ray microscopy techniques allow the study of specimens with unprecedented spatial resolution, down to 10 nm, using soft and medium X-ray photon energies, though at the expense of the field of view (FOV). One of the approaches to increase the FOV to square millimetres is raster-scanning of the specimen using a single nanoprobe; however, this results in a long data acquisition time. This work employs an array of inclined biconcave parabolic refractive multi-lenses (RMLs), fabricated by deep X-ray lithography and electroplating to generate a large number of long X-ray foci. Since the FOV is limited by the pattern height if a single RML is used by impinging X-rays parallel to the substrate, many RMLs at regular intervals in the orthogonal direction were fabricated by tilted exposure. By inclining the substrate correspondingly to the tilted exposure, 378000 X-ray line foci were generated with a length in the centimetre range and constant intervals in the sub-micrometre range.
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