Search

The thermal decomposition of Fe x (CO) y precursors for the synthesis of nanoparticles of iron carbides and their superstructures with sizes ranging from 2.8 to 15.1 nm is developed using imidazolium-based ionic liquids as solvents, stabilizers, and carbon source. A study of the influence of some synthesis parameters such as the heating temperature, nature, and concentration of the iron carbonyl precursor and chain length of the N-alkyl substituent on the imidazolium ring on the size and organization of the iron carbide nanoparticles is presented. These iron carbides nano-objects were characterized by infra-red spectroscopy, transmission electronic microscopy, powder X-ray diffraction, Mossbauer spectroscopy, and magnetic analyses.

International audience; This article focuses on the possibility of exciting some lanthanides (Ce3+, Tb3+, Gd3+, and Eu3+) by ultrasound in aqueous solutions. Depending on the lanthanide ions and on the acoustic cavitation conditions (single-bubble or multibubble systems), the excitation mechanism is shown to be photoexcitation (e.g., for Ce3+) or collision-induced excitation (e.g., for Tb3+). The sonoluminescence of Tb3+ is studied in detail at various ultrasonic frequencies, allowing quantification of the amount of quenching. The latter is much stronger in sonoluminescence than in photoluminescence due to the particular properties of acoustic cavitation. Complexation with citrate ions enhances manifold sonoluminescence of lanthanides due to reduction of intra- and inner-molecular quenching.

International audience; There are typically signs of light degradation of ionic liquids by pyrolysis when used in electrochemistry or when submitted to high heat or to ultrasound irradiation for chemical reactions. Cavitation observed through sonoluminescence from dry hydrophobic ionic liquids under sonication leads to degradation by pyrolysis at the level of traces. The degradation products can hinder recycling ionic liquids and, in turn, hinder the beneficial of their use and development of efficient large-scale processes. Unfortunately, various experimental limitations have prevented structural determination. The problems include the following: ionic liquids are almost non-volatile, which excludes the use of classical analytical techniques, and degradation products are produced at very low concentrations, which complicates extraction and analysis. Reported here is the first structural determination of the degradation products of a hydrophobic bis(trifluoromethylsulfonyl)imide-based ionic liquid under ultrasonic irradiation.

A kinetic isotope effect in Pu(V) disproportionation has been observed in nitric acid solution under the effect of power ultrasound with intensity 0.9W·cm−2 and frequency 22 kHz. The isotope separation coefficient α for242Pu/239Pu isotopes was found to be 1.0081 at 20°C. Without sonication the k.i.e. was not observed. The rate constant of Pu(V) disproportionation was found to be accelerated under sonication. The rate constant determined was (5.7±0.6)·10−3 12·mol−2·s−1 atl=0.9 W·cm−2,v=22 kHz, [HNO3]=0.5 mol·l−1 andT=20°C. It is supposed that the acceleration of Pu(V) disproportionation and the kinetic isotope effect are due to the activation of plutonoyl groups in the interface between the cavitation bubble and the bulk solvent.

International audience; The sonoluminescence (SL) spectra of OH(A2Σ+) excited state produced during the sonolysis of water sparged with argon were measured and analyzed at various ultrasonic frequencies (20, 204, 362, 609, and 1057 kHz) in order to determine the intrabubble conditions created by multibubble cavitation. The relative populations of the OH(A2Σ+) v′ = 1–4 vibrational states as well as the vibronic temperatures (Tv, Te) have been calculated after deconvolution of the SL spectra. The results of this study provide evidence for nonequilibrium plasma formation during sonolysis of water in the presence of argon. At low ultrasonic frequency (20 kHz), a weakly excited plasma with Brau vibrational distribution is formed (Te ∼ 0.7 eV and Tv ∼ 5000 K). By contrast, at high-frequency ultrasound, the plasma inside the collapsing bubbles exhibits Treanor behavior typical for strong vibrational excitation. The Te and Tv values increase with ultrasonic frequency, reaching Te ∼ 1 eV and Tv ∼ 9800 K at 1057 kHz.

Sonochemical synthesis of platinum nanoparticles (Pt NPs) in formic acid solutions and pure water was investigated using a 20 kHz ultrasonic irradiation. The obtained results gave new insights on the underneath Pt(IV) reduction mechanism in formic acid media under argon and in pure water under Ar/CO atmosphere. It was shown that in pure water sonochemical reduction of platinum ions occurs by hydrogen issued from homolytic water molecule split. Pt(IV) ion reduction appears to be a very slow process under argon atmosphere in pure water due to formation of oxidizing species like OH radicals and H(2)O(2) leading to reoxidation of intermediate Pt(II) ions. Sonochemical reduction is accelerated manifold in the presence of formic acid or Ar/CO gas mixture. Solution and gas-phase analyses reveal that both CO and HCOOH act as OH(.) radical scavenger and reducing agent under ultrasonic irradiation. Their ability to reduce platinum ions at room temperature is enhanced due to the local heating in the liquid shell surround the cavitation bubble. An innovative synthesis route for monodispersed Pt NPs in pure water without any templates or capping agents in the presence of Ar/CO gas mixture is then proposed. Obtained Pt NPs within the range of 2-3 nm exhibited a strong stability towards sedimentation in water. Since Ar/CO atmosphere is the only restriction of the process, this procedure can be applied in various media and is also compatible with a large array of experimental conditions.

By means of theoretical modeling and experimental synthesis and characterization, we investigate the structural properties of amorphous Zr-Si-C. Two chemical compositions are selected, Zr0.31Si0.29C0.40 and Zr0.60Si0.33C0.07. The amorphous structures are generated in the theoretical part of our work, by the stochastic quenching (SQ) method, and detailed comparison is made as regards structure and density of the experimentally synthesized films. These films are analyzed experimentally using X-ray absorption spectroscopy, transmission electron microscopy and X-ray diffraction. Our results demonstrate for the first time a remarkable agreement between theory and experiment concerning bond distances and atomic coordination of this complex amorphous metal carbide. The demonstrated power of the SQ method opens up avenues for theoretical predictions of amorphous materials in general., 29 pages, 11 figures

Ultrasounds excite uranium: Uranyl ions exhibit an ultrabright multibubble sonoluminescence in cooled H3PO4 solutions exposed to high-frequency ultrasound. The mechanism of UO22+ excitation seems to vary with uranium concentration: sonophotoluminescence dominates in diluted solutions, and collisional excitation would contribute in concentrated UO22+ solutions

International audience; Experimental techniques as neutron diffraction (ND) with isotopic substitution (NDIS), extended X-ray absorption fine structure spectroscopy (EXAFS), and quasielastic neutron scattering (QENS), in combination with molecular dynamics (MD) simulations, are usually applied to the study of noncrystalline solids, but they are also very useful for the study of complex systems, where the short range order provides an insight of its structure and dynamics. Here, they are used in the study of the coordination of the Sm3þ in the interlayer of hydrated synthetic montmorillonite and hectorite. The ND results indicate that not all oxygen atoms in the first coordination shell of the Sm3þ belong to water molecules, supporting the formation of theSm3þ inner-sphere complex.On the other hand, the other techniques suggest that the adsorbed Sm3þ cations form outer-sphere complexes with the clay surface. The hypothesis making compatible all results is that there are different Sm species adsorbed in the clay interlayer: a part of Sm is in the Sm3þ cationic form, forming outer-sphere adsorption complexes, another part is hydrolyzed and present in the interlayer space as Sm(OH)2þ, SmðOHÞþ 2 , or SmðOHÞ0 3 species. The latter are more hydrophobic than Sm3þ cations and can be dehydrated and are able to stick to the clay surface.

The development of new efficient afterglow phosphors is currently hampered by a limited understanding of the persistent luminescence mechanism. Radioluminescence (RL) and x-ray absorption measurements on the persistent phosphor SrAl${}_{2}$O${}_{4}$:Eu,Dy were combined to reveal possible valence state changes for the rare earth (co)dopants. Traps in the phosphor material are quickly filled when exposing thermally emptied SrAl${}_{2}$O${}_{4}$:Eu,Dy powder to x rays. On the same time scale a partial oxidation of Eu${}^{2+}$ to Eu${}^{3+}$ is observed by x-ray absorption near-edge spectroscopy (XANES), while for the trivalent dysprosium the valence state remains unchanged. The impact of these observations on the recently proposed models for persistent luminescence is discussed.

The fields of bioscience and nanomedicine demand precise thermometry for nanoparticle heat characterization down to the nanoscale regime. Since current methods often use indirect and less accurate techniques to determine the nanoparticle temperature, there is a pressing need for a direct and reliable element-specific method. In-situ extended X-ray absorption fine structure (EXAFS) spectroscopy is used to determine the thermo-optical properties of plasmonic branched gold nanoparticles upon resonant laser illumination. With EXAFS, the direct determination of the nanoparticle temperature increase upon laser illumination is possible via the thermal influence on the gold lattice parameters. More specifically, using the change of the Debye-Waller term representing the lattice disorder, the temperature increase is selectively measured within the plasmonic branched nanoparticles upon resonant laser illumination. In addition, the signal intensity shows that the nanoparticle concentration in the beam more than doubles during laser illumination, thereby demonstrating that photothermal heating is a dynamic process. A comparable temperature increase is measured in the nanoparticle suspension using a thermocouple. This good correspondence between the temperature at the level of the nanoparticle and at the level of the suspension points to an efficient heat transfer between the nanoparticle and the surrounding medium, thus confirming the potential of branched gold nanoparticles for hyperthermia applications. This work demonstrates that X-ray absorption spectroscopy-based nanothermometry could be a valuable tool in the fast-growing number of applications of plasmonic nanoparticles, particularly in life sciences and medicine.

For the first time, acoustic cavitation was used as a source of excitation for photoactive species contained in an extended solid phase. Spectroscopic measurements performed during the sonication of (Ce0.9Tb0.1)PO4 sintered pellets with 20 kHz power ultrasound in cooled water under argon showed the Tb(III) light emission resulting from 5D4–7Fj f–f transitions. The emission spectra were measured as a function of the focus within the cavitation zone, as a function of the distance between the pellet and the ultrasonic horn, or using sonoluminescence quenchers (air or tert-butanol). The experiments revealed that Tb(III) sonoluminescence results from a solid-state Tb(III) excitation by photons emitted from the cloud of ultrasonically driven cavitation bubbles, referred to as “sonophotoluminescence”.

The present work analyses the mechanism of W(2)C/C nanocomposite formation during sonolysis of W(CO)(6) in diphenylmethane (DPhM) solutions. Carbon supported WC(x) nanoparticles attract much interest as an alternative fuel cell electrocatalysts. Sonolysis of neat DPhM under the effect of 20 kHz power ultrasound in argon at 80 °C yields a sonopolymer as a solid product and acetylene, hydrogen, methane, diacetylene and benzene as gaseous products. Diacetylene is formed due to the secondary sonochemical dimerisation of acetylene obtained at the primary stage of DPhM sonolysis. FTIR and μ-Raman studies show that the sonopolymer consists of a mixture of some polymeric partially oxidized aromatic species, and disordered carbon. Sonolysis of W(CO)(6) in diphenylmethane solutions follows the first order kinetics. This process yields monodispersed 2-3 nm X-ray amorphous WC(x) nanoparticles embedded in amorphous sonopolymer. The annealing of air sensitive as-prepared solids in an inert atmosphere at 600 °C causes formation of stable W(2)C/C nanocomposite with W(2)C average particle size in the range of 4-7 nm and hexagonal carbon fine particles with the average size of 30-40 nm. Kinetic study revealed that tungsten carbide is formed inside the cavitation bubble due to the reaction of tungsten nanoparticles originated from primary sonolysis of W(CO)(6) with acetylene produced as a result of diphenylmethane sonochemical degradation.

The industrial treatment of spent nuclear fuel is based upon a hydrometallurgical process in nitric acid medium. In order to minimize the volume of radioactive waste it seems interesting to generate the reactive species in situ in such solutions using ultrasonic irradiation without addition of salt-forming reagents. This review summarizes for the first time the versatile sonochemical processes with uranium, neptunium and plutonium in homogeneous nitric acid solutions and heterogeneous systems. The dissolution of refractory solids, ultrasonically driven liquid-liquid extraction and the sonochemical degradation of the volatile products of organic solvent radiolysis issued from PUREX process are considered. Also the guidelines for required further work to ensure successful application of the studied processes at industrial scale are discussed.

The kinetics and mechanism of formic acid sonochemical degradation were studied at ultrasonic frequencies of 20, 200, and 607 kHz under argon atmosphere. Total yield of HCOOH sonochemical degradation increases approximately 6-8-fold when the frequency increased from 20 to 200 or to 607 kHz. At low ultrasonic frequencies, HCOOH degradation has been attributed to oxidation with OH(•) radicals from water sonolysis and to the HCOOH decarboxylation occurring at the cavitation bubble-liquid interface. With high-frequency ultrasound, the sonochemical reaction is also influenced by HCOOH dehydration. Whatever the ultrasonic frequency, the sonolysis of HCOOH yielded H(2) and CO(2) in the gas phase as well as trace amounts of oxalic acid and formaldehyde in the liquid phase. However, CO and CH(4) formations were only detected under high-frequency ultrasound. The most striking difference between low-frequency and high-frequency ultrasound is that the sonolysis of HCOOH at high ultrasonic frequencies initiates Fischer-Tropsch hydrogenation of carbon monoxide.

We present a high-resolution in situ imaging and localization method of energetic particle beams. Recording of the scattered radiation from a thin featureless foil, placed in the path of the beam, and taken with a pinhole or coded aperture camera arrangement magnifies beam movements at the sensor. At the same time, a magnified image of the beam is available with an exceptional signal-to-noise ratio. We show measurement results of the level of precision that can be achieved and compare them to theoretical limits based on the signal-to-noise levels. © 2011 Optical Society of America.

The equilibrium isotope effect in tin(II)-tin(IV) electron-exchange systems has been studied by a redox chromatography method using an anion-exchange resin. It was shown that the light isotopes are concentrated in tin(II) preferably. The values of the isotope separation coefficient (α) for 112Sn and heavy isotopes were determined at 82°C and 5.5 mol dm−3 HCl. The dependence of α on isotopic mass ratio was found to be defined by the curve reaching top values of α for isotopes heavier than 120Sn.

The industrial treatment of spent nuclear fuel is based upon a hydrometallurgical process in nitric acid medium. In order to minimize the volume of radioactive waste it seems interesting to generate the reactive species in situ in such solutions using ultrasonic irradiation without addition of salt-forming reagents. This review summarizes for the first time the versatile sonochemical processes with uranium, neptunium and plutonium in homogeneous nitric acid solutions and heterogeneous systems. The dissolution of refractory solids, ultrasonically driven liquid-liquid extraction and the sonochemical degradation of the volatile products of organic solvent radiolysis issued from PUREX process are considered. Also the guidelines for required further work to ensure successful application of the studied processes at industrial scale are discussed.

Power ultrasound (20 kHz, Iac = 20−56 W cm−2) was used to investigate physical and chemical effects of acoustic cavitation at the water−glass interface. Physical effects were characterized with different techniques of microscopy (optical, SEM, AFM) and were shown to increase and evolve as a function of sonication duration according to two distinctive periods: (i) an incubation period that initiates weak points on a glass surface, which may be the result of acoustically created shock-waves, and (ii) a second period of erosion, which is related to direct impact fracture erosion of the material. Chemical analysis of water (ICP-OES), after ultrasonic treatment, clearly indicates that bubble collapse at the water−glass interface initiates not only mechanical erosion but also accelerates the leaching processes of the glass components.

This paper describes, for the first time, a simple method for the synthesis of uranyl aluminate (URAL) nanoparticles. URAL was prepared by U(VI) hydrolytic precipitation with ammonia at pH = 11 in the presence of mesoporous alumina MSU-X under 20 kHz of sonication followed by annealing of the obtained solids at 800 degrees C. TEM, XAFS, powder XRD, and (27)Al MAS NMR studies revealed that the speciation of uranium in this system strongly depends on uranium concentration. The sample with 5 wt % of uranium yields air-stable nanoparticles ( approximately 5 nm) of URAL. Presumably, UO(2)(2+) cations in this compound are coordinated with bidentate AlO(2)(-) groups. The increase of uranium concentration to 30 wt % causes mostly formation of U(3)O(8) fine particles ( approximately 50 nm) and small amounts of URAL.

A confocal setup based on polycapillary half-lenses was used to demonstrate three-dimensional (3D) spatially resolved mu-XANES in fluorescence detection mode at the DUBBLE XAS station of the ESRF (BM26A). The incoming beam was focused using a polycapillary half-lens and a second glass polycapillary was placed in front of the energy dispersive detector to establish the confocal detection. The full-width-half-maxima along the main axes of the resulting ellipsoidal detection volume were 18.5 x 12.0 x 10.0 microm(3) at the Cu K-edge. The confocal mu-XANES mode is applied in the 3D resolved study of mineral inclusions in rare natural diamonds at the Fe K edge.

International audience

A focusing system based on a polycapillary half-lens optic has been successfully tested for transmission and fluorescence µ-X-ray absorption spectroscopy at a third-generation bending-magnet beamline equipped with a non-fixed-exit Si(111) monochromator. The vertical positional variations of the X-ray beam owing to the use of a non-fixed-exit monochromator were shown to pose only a limited problem by using the polycapillary optic. The expected height variation for an EXAFS scan around the Fe K-edge is approximately 200 µm on the lens input side and this was reduced to ∼1 µm for the focused beam. Beam sizes (FWHM) of 12–16 µm, transmission efficiencies of 25–45% and intensity gain factors, compared with the non-focused beam, of about 2000 were obtained in the 7–14 keV energy range for an incoming beam of 0.5 × 2 mm (vertical × horizontal). As a practical application, an As K-edge µ-XANES study of cucumber root and hypocotyl was performed to determine the As oxidation state in the different plant parts and to identify a possible metabolic conversion by the plant.

The synthesis of marokite CaMn(2)O(4) nanowires using a hydrothermal method is reported. Transmission electron microscopy and electron diffraction measurements show that the nanowires are polycrystalline in nature with diameters between 10 and 20 nm and lengths ranging from approximately 100 to 500 nm. Most interestingly, in contrast with the bulk material, magnetization measurements show that these nanowires exhibit ferromagnetic ordering with a Curie temperature (T(C)) of approximately 40 K.

Laboratory scale 20 kHz sonochemical reactors with different geometries have been tested using thermal probes, the kinetics of H 2 O 2 formation, and the kinetics of diphenylmethane (DPhM) sonochemical darkening. Results revealed that the overall sonochemical reaction rates in H 2 O and DPhM are driven by the total absorbed acoustic energy and roughly independent the geometry of the studied reactors. However, the sonochemical efficiency, defined as η = VG / S , where G is a sonochemical yield of H 2 O 2 , V is a volume of sonicated liquid, and S is a surface of the sonotrode, was proved to increase with the decrease of S . This phenomenon was explained by growing of the maximum cavitating bubble size with ultrasonic intensity and its independence towards the specific absorbed acoustic power. For the cleaning bath reactor the kinetics of the sonochemical reactions in H 2 O and DPhM depends strongly on the reaction vessel materials: the reaction rates decreased with the increase of the materials elasticity. Kinetic study of H 2 SO 4 sonolysis using a sonoreactor without direct contact with titanium sonotrode showed that sulphate anion is an effective scavenger of OH radicals formed during water sonolysis.

The complex [BuMeIm]2[UCl6] was characterized in the solid state and in a solution of [BuMeIm][Tf2N] room temperature ionic liquid using single-crystal XRD, EXAFS, visible absorption spectroscopy and NMR techniques.The structure of solid [BuMeIm]2[UCl6] contains two crystallographically independent formula units (U(1) and U(2)).The U–Cl distances in Click to view the MathML source anions range from 2.576(6) to 2.638(4) Å, the average values being 2.621(6) and 2.601(8) Å for U(1) and U(2), respectively.The BuMeIm+ cations have four different conformations of C4H9 chains.The shortest distances between the centres of the five-member rings of the BuMeIm+ cations and U atoms of [UCl6]2− anions are in the range 5.53–4.90 Å.Single-crystal XRD data reveal the existence of a hydrogen bond between the most acidic H atom of the imidazolium ring (C2) and the chloride anion of the Click to view the MathML source octahedron, with the shortest distance Clcdots, three dots, centeredH(C2) equal to 2.57 Å.Quantitative EXAFS measurements indicate that the octahedral complex Click to view the MathML source(RU–Cl = 2.632(2) Å) is the predominant chemical form of U(IV) in [BuMeIm][Tf2N] solution.Visible absorption spectroscopy and 1H NMR spectroscopy confirm the existence of hydrogen bonding between theClick to view the MathML source anion and the acidic proton of the BuMeIm+ cation in RTIL solution, similar to that in the solid state.

Magnetically tunable, high-density arrays of coaxial nanocables within anodic aluminum oxide (AAO) membranes have been synthesized. The nanocables consist of magnetite nanowires surrounded by cobalt nanotube sheaths and cobalt nanowires surrounded by magnetite nanotube sheaths. These materials are a combination of separate hard (Co) and soft (Fe3O4) magnetic materials in a single nanocable structure. The combination of two or more magnetic materials in such a radial structure is seen as a very powerful tool for the future fabrication of magnetoresistive, spin-valve and ultrafast spin-injection devices with nonplanar geometries. The nanocable arrays were prepared using a supercritical-fluid inclusion process, whereby the nanotube was first deposited onto the pore walls of the nanoporous membranes and subsequently filled with core material to form coaxial nanocables. In essence, this paper describes a technique for placing novel magnetic technologies into well-defined building blocks that may ultimately lead to new multifunctional devices, such as spin valves and high-density magnetic storage devices.

wird nachgereicht

Sonolysis of diphenylmethane (DPhM) has been studied under the effect of 20 kHz ultrasound (absorbed acoustic power 0.45 W/ml, surface area of sonotrode 1 cm2, volume of sonicated solution 100 ml) under argon at 60 °C. The solid product of the sonolysis was characterized by elemental analysis, FTIR, 13C MAS NMR, TGA/DSC, XRD and TEM techniques. It was found that the sonolysis of DPhM causes formation of the polymer with the composition similar to crosslinked polystyrene. Assumed mechanism of DPhM sonolysis consists of DPhM molecules dissociation inside the cavitating bubble. Secondary radical scavenging and radical recombination processes yields the sonopolymer in the liquid phase. The breakdown of the aromatic ring during DPhM sonolysis confirms that a very high temperature established in the cavitating bubble.

Nitric acid solutions will be created from the dissolution of Hanford K Basin sludge. These acidic dissolver solutions must be made alkaline by treatment with NaOH solution before they are disposed to ~ the Tank Waste Remediation System on the Hanford Site. During the alkali treatments, sodium diuranate, hydroxides of iron and aluminum, and radioelements (uranium, plutonium, and americium) will precipitate from the dissolver solution. Laboratory tests, discussed here, were pefiormed to provide information on these precipitates and their precipitation behavior that is important in designing the engineering flowsheet for the treatment process. Specifically, experiments were conducted to determine the optimum precipitation conditions; the completeness of uranium, plutonium, and americium precipitation; the rate of sedimentation; and the physico-chemical characteristics of the solids formed by alkali treatment of simulated acidic dissolver solutions. These experiments also determined the redistribution of uranium, plutonium, and americium flom the sodium di~ate and iron and al&inurn hydroxide precipitates upon contact with carbonate- and EDTA-bearing simulated waste solutions. Note: EDTA is the tetrasodium salt of ethylenediaminetetraacetate.

Europium doped zinc thiogallate, ZnGa2S4:Eu2+, has been reported as a saturated green emitting phosphor, suitable as conversion phosphor in white LEDs for lighting or displays. Up to now, no direct proof for the incorporation of Eu2+ in ZnGa2S4 has been given. We combined X-ray diffraction (XRD), cathodoluminescence in electron microscopy (SEM-CL) and X-ray absorption spectroscopy (XAS) to study the incorporation of the europium ions in the host material. The previously reported green luminescence was found to originate from small amounts of unintentionally formed EuGa2S4, and not from europium ions incorporated into ZnGa2S4. EuGa2S4 has a low quantum efficiency (< 20%) and shows strong thermal quenching, already below room temperature. The XAS data analysis suggests that a certain amount of europium might occupy octahedral voids inside the zinc thiogallate lattice in a divalent state. The zinc ion next to these interstitial dopants is then removed for charge compensation. Notwithstanding the possible, but limited, incorporation of Eu2+ in ZnGa2S4, these ions do not activate any luminescence as was shown with SEM-CL.

Molecular-scale chemical information about solutions is of primary importance in the understanding of liquid-liquid extraction phenomena. From this point of view, NMR spectroscopy is a useful tool. However, in the field of the nuclear fuel reprocessing, this technique needs to overcome certain intrinsic limitations, including the presence of both paramagnetic metals and radioactivity. Because of the experimental difficulties encountered, paramagnetic data about actinides is scarce but nevertheless required in order to take advantage of information contained in the electron-nucleus interactions. This study will present two speciation studies dealing with Am(III) and U(IV) complexes in solution. Am(III) paramagnetism was found to be weak enough to observe a complex formed with a tetrapodal hexadentate N,O ligand in an aqueous solution. Although U(IV) paramagnetism is stronger, due to a fast chemical exchange with the ionic liquid used it was possible to extract structural information arising from 1H NMR spectra analysis. Results obtained in solution are consistent with X-Ray data which indicate that ligand-metal interactions mainly come from hydrogen bonding.

Glass polycapillary optics are shown to be easy to use focusing optics for bending magnet XAS stations. These achromatic optics have acceptances of several mm horizontally and vertically, while their angular acceptances can be matched to the source divergence by the design of the polycapillary. A polycapillary half-lens based focusing system was successfully tested for transmission and fluorescence µ-XAS at the DUBBLE beamline (BM26A, ESRF) and the feasibility of confocal µ-XANES in fluorescence mode is presented. Transmission efficiencies of 25-45% with flux density gain factors of about 2000 and beam sizes of 10-20 µm were obtained in the 7-14 keV energy range. Although the polycapillary optic has a smoothly changing energy dependent transmission efficiency, the amplitude and shape of the EXAFS oscillations are not influenced by this. The focusing properties of the polycapillary lens cancel slight vertical motions of the incoming X-ray beam, resulting in a fixed µ-beam spot in the focal plane, making polycapillaries also suitable optic in combination with a non-fixed exit monochromator. In addition, by mounting a second polycapillary half-lens in front of an energy dispersive detector, a confocal set-up is obtained, which restricts the part of the sample seen by the detector to a microscopic volume of about 20×20×15 µm3 at the Fe K absorption edge for example.

We have investigated two in situ methods of measuring x-ray beam parameters such as integrated intensity, position, and intensity distribution. These virtually transparent methods both rely on the collection of scattered radiation from a thin amorphous foil. The scattered radiation is collected by an active pixel sensor placed below the foil, well out of the direction of the beam path. These methods measure a cross-sectional image of the beam as opposed to a profile or beam centroid position provided by existing in situ detection methods. We present the results of measurements taken at a third generation synchrotron radiation source and provide analytical methods of deriving beam profile, position, and absolute intensity.

The kinetic isotope effect has been observed for γ-radiolytic reduction of PbII in aqueous formate solutions and the values of the isotope separation coefficient (α) for 208/207Pb, 208/206Pb and 208/204pb have been determined.

Data on the separation of uranium isotopes by chemical isotopic exchange have been reviewed. Promising methods for enriching uranium have been compared. The bibliography contains 120 references.