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A new parallel-beam wavelength dispersive (PB-WDS) X-ray emission spectrometer was constructed at the external proton beamline at the Microanalytical Centre of the Joˇzef Stefan Institute in Ljubljana. The spectrometer combines polycapillary X-ray optics for efficient X-ray collection with diffraction on a flat crystal analyzer and achieves energy resolution in the eV range. The whole set-up is enclosed within a He bag to be able to operate in the tender X-ray energy range. The basic design is described together with the results of characterization measurements yielding the main operation characteristics. Finally, an application for the micro-PIXE analysis of biological tissue is demonstrated exploiting both spatial and energy resolution of the new set-up.

High energy resolution X-ray emission spectroscopy was used to study the multiple ionization satellites in the K X-ray spectra of titanium induced by target irradiation with MeV alpha particles. Beam energies of 3–5 MeV were used to explore the beam energy dependence. In addition, several titanium binary oxides excited with 5 MeV beam were measured to study also the chemical bonding effects on the multiple ionization satellites. Energy shifts and intensities of the satellites corresponding to one and two L-shell vacancies were determined from the measured spectra. The results will be used to refine the existing experimental alpha particle induced multiple ionization satellite database which is needed to improve the accuracy of PIXE analysis using alpha particle beams, including the PIXE mode of the Mars alpha particle X-ray spectrometers.

Kα x-ray emission induced by 2 MeV protons in thick Ti metal, TiO, Ti2O3, TiO2, MgTiO3, FeTiO3, TiC, TiN, TiB2, Cr metal, Cr2O3, CrO2, CrO3, K2Cr2O7 targets was measured using a wavelength dispersive spectrometer employing Johansson geometry to study chemical sensitivity of X-ray spectra. In the spectra the main Kα1 and Kα2 components as well as the KαL1 multiple ionization satellites were clearly resolved. The Kα1 and Kα2 peak positions and widths were extracted directly from the measured spectra in a consistent way. The results were compared with the existing data obtained by proton and photon induced ionization mechanisms, with the results of multiplet calculations, and with the observed chemical effects found in the related experimental Kβ spectra measured on the same Ti and Cr compounds at earlier times. The results obtained confirm linear correlations of the Kα1 first moments (M1) and the Kα center of gravity energy shifts with the central metal formal oxidation state, as well as between the Kα1 line widths and the Kα1 - Kβ1 M1 and/or centre of gravity energy shifts. The Kα energy shifts calculated by multiplet structure method for Cr compounds agreed with the experimentally obtained trends. Keywords: X-ray emission spectroscopy, High resolution X-ray spectra, Ti and Cr compounds, PIXE, Multiple ionization satellites.

The journal of physical chemistry / C 126(12), 5435 - 5442 (2022). doi:10.1021/acs.jpcc.1c10622, X-ray Raman spectroscopy (XRS) is an emerging spectroscopic technique that utilizes inelastic scattering of hard X-rays to study X-ray absorption edges of low Z elements in bulk material. It was used to identify and quantify the amount of carbonyl bonds in a cathode sample, in order to track the redox reaction inside metal–organic batteries during the charge/discharge cycle. XRS was used to record the oxygen K-edge absorption spectra of organic polymer cathodes from different multivalent metal–organic batteries. The amount of carbonyl bond in each sample was determined by modeling the oxygen K-edge XRS spectra with the linear combination of two reference compounds that mimicked the fully charged and the fully discharged phases of the battery. To interpret experimental XRS spectra, theoretical calculations of oxygen K-edge absorption spectra based on density functional theory were performed. Overall, a good agreement between the amount of carbonyl bond present during different stages of battery cycle, calculated from linear combination of standards, and the amount obtained from electrochemical characterization based on measured capacity was achieved. The electrochemical mechanism in all studied batteries was confirmed to be a reduction of double carbonyl bond and the intermediate anion was identified with the help of theoretical calculations. X-ray Raman spectroscopy of the oxygen K-edge was shown to be a viable characterization technique for accurate tracking of the redox reaction inside metal–organic batteries., Published by Soc., Washington, DC

In this work, valence-to-core (VtC) Kβsulfur X-ray emission spectroscopy (XES) was used to perform quantitative analysis of different sulfur compounds produced in a lithium sulfur (Li–S) battery during discharge. The analysis is based on the theoretical sulfur KβXES spectra obtained from ab initio quantum chemical calculations based on density functional theory. The emphasis is given to the Kβsulfur XES spectra of the polysulfide molecules (Li2Sx, x = 2,…,8) produced electrochemically within the Li–S battery. Ab initio molecular dynamics calculations are used further to calculate also the Kβspectra of Li2Sx dissolved in a model solvent. Calculated spectra were directly compared with the experimental ones collected with a Johansson type tender XES spectrometer on laboratory synthesized Li2Sx reference standards and pre-cycled battery cathodes. These results demonstrate that sulfur VtC XES can be used effectively to quantitatively analyze electrochemical sulfur conversion, also in a smaller laboratory without the need for large scale synchrotron facilities.

Wavelength-dispersive X-ray spectrometry is used to examine the influence of multiple ionization satellites induced by 3–5 MeV energy helium ion beams upon the accuracy of particle-induced X-ray emission analysis (PIXE). The work extends our prior study of elements magnesium, aluminum and silicon and their oxides to elements phosphorus, chlorine, potassium, calcium, titanium and chromium and, for the latter two, their oxides. Fitting of the spectra with Voigtian peaks enables construction of a database that comprises the mean energies and the relative intensities of up to four distinct satellite groupings. This database provides an empirical means for inclusion of one peak per satellite group when modelling energy-dispersive spectra. This is a useful step towards improving the accuracy of PIXE analysis of materials using helium beams ; an example of this is provided using a spectrum recorded by the Curiosity rover on Mars.

International audience; In a lithium/sulfur (Li/S) battery, the reduction of sulfur along discharge involves a particular mechanism, where the active material successively dissolves into the electrolyte to form lithium polysulfides intermediate species (Li2Sx), with x being a function of state of charge. In this work, sulfur K-edge Resonant Inelastic X-ray Scattering measurements were applied for the characterization of different Li2Sx polysulfide standard solutions. High Energy Resolution Fluorescence Detected X-ray Absorption Spectroscopy allowed to separate clearly the pre-edge absorption peak corresponding to terminal sulfur atoms from the main absorption peak due to internal atoms, and to evaluate quantitatively the evolution of the peak area ratio as a function of the polysulfide chain length. Results of this experimental work demonstrate that the normalized area of the pre-edge is a reliable fingerprint of Li2Sx mean chain length in agreement with recent theoretical predictions. As a perspective, this work confirms that operando HERFD XAS can be used to differentiate polysulfides mean composition, which is key issue in the characterization of Li/S cells.

The Curiosity rover’s alpha particle X-ray spectrometer employs simultaneous XRF and PIXE to analyze rock and soil samples on the Martian surface. The PIXE is accomplished by alpha particle emission from 244Cm, and the XRF by the L X-rays from the daughter. Recent work [1] has shown that fits to these spectra, which extend over a 23 keV range, are improved by accounting rigorously for both X-ray detector non-linearity and the alpha-induced multiple ionization satellites. This work necessitated the insertion of an interim satellite database into the GUPIX-based fitting code GUAPX. The database was assembled from a rather sparse literature and involved considerable extrapolation and interpolation. For 3- 5 MeV alphas, the summed intensity in the KL1 , KL2 , KL3 satellites is of similar order to that of the KL0 diagram line. It is clear that the accuracy of laboratory-based PIXE with alpha particles can be improved by including these in the spectrum fitting procedure. We have therefore started an effort to refine and extend the interim satellite database, using WDX spectroscopy at IJS and IRB. Work has been completed on magnesium, aluminum, silicon and their oxides. The spectra below are from Si and SiO2 ; all individual Voigtians are shown. Comparison of our results for individual line energies and intensities with those of the database has enabled small corrections to the latter. The work will now proceed to elements of higher atomic number. [1] J. L. Campbell, B. Ganly, C. M. Heirwegh, J. A. Maxwell, Nucl. Instr. Meth. B414, 2018, 38.

International audience; The electronic structure of AgxMo9Se11 as a potential material for thermoelectric applications was studied using high- energy-resolution fluorescence-detection X-ray absorption spectros- copy (HERFD-XAS) and the resonant inelastic X-ray scattering (RIXS) technique. The experiments were supported by first-principle calculations using density functional theory (DFT). The analysis of obtained spectra indicate the presence of subvalent (less than 1+) Ag in AgxMo9Se11. The advanced HERFD-XAS measurements allowed us to resolve the contribution of the electronic states at the Fermi level of AgxMo9Se11 and to monitor its dependence on the x value. A comparison of the experimental data with the results of the DFT calculations suggests the importance of the Ag2-type sites with the shortest Ag−Se distance for affecting the properties of AgxMo9Se11.

High energy resolution X-ray emission spectroscopy employing wavelength dispersive (WDS) crystal spectrometers can provide energy resolution on the level of core-hole lifetime broadening of the characteristic emission lines. While crystal spectrometers have been traditionally used in combination with electron excitation for major and minor element analysis, they have been rarely considered in proton induced X-ray emission (PIXE) trace element analysis mainly due to low detection efficiency. Compared to the simplest flat crystal WDS spectrometer the efficiency can be improved by employing cylindrically or even spherically curved crystals in combination with position sensitive X-ray detectors. When such spectrometer is coupled to MeV proton excitation, chemical bonding effects are revealed in the high energy resolution spectra yielding opportunity to extend the analytical capabilities of PIXE technique also towards chemical state analysis. In this contribution we will focus on the high energy resolution PIXE (HR-PIXE) spectroscopy in the tender X-ray range performed in our laboratory with our home-built tender X-ray emission spectrometer. Some general properties of high energy resolution PIXE spectroscopy in the tender X-ray range are presented followed by an example of sulfur speciation in biological tissue illustrating the capabilities as well as limitations of HR-PIXE method used for chemical speciation in the tender X-ray range.

Magnesium–sulfur batteries are considered as attractive energy-storage devices due to the abundance of electrochemically active materials and high theoretical energy density. Here we report the mechanism of a Mg–S battery operation, which was studied in the presence of simple and commercially available salts dissolved in a mixture of glymes. The electrolyte offers high sulfur conversion into MgS in the first discharge with low polarization. The electrochemical conversion of sulfur with magnesium proceeds through two well-defined plateaus, which correspond to the equilibrium between sulfur and polysulfides (high-voltage plateau) and polysulfides and MgS (low-voltage plateau). As shown by XANES, RIXS (resonant inelastic X-ray scattering), and NMR studies, the end discharge phase involves MgS with Mg atoms in a tetrahedral environment resembling the wurtzite structure, while chemically synthesized MgS crystallizes in the rock-salt structure with octahedral coordination of magnesium.

A new parallel beam wavelength dispersive X-ray emission spectrometer for high energy resolution PIXE analysis using focused proton microbeam has been constructed and installed at the microprobe of the J. Stefan Institute. Polycapillary X-ray optics is used to enhance the solid angle of X-ray collection and to transform collected proton-induced X-rays into quasi parallel beam which is analyzed using diffraction on a flat crystal. The spectrometer is installed in a vacuum chamber and operates in the 2–10 keV energy range. The main characteristics and operational properties are presented together with the results of first characterization measurements. Finally, two selected experimental examples are given illustrating the capabilities of the spectrometer in PIXE analysis and fundamental research in atomic physics.

Stochastic processes are highly relevant in research fields as different as neuroscience, economy, ecology, chemistry, and fundamental physics. However, due to their intrinsic unpredictability, stochastic mechanisms are very challenging for any kind of investigations and practical applications. Here we report the deliberate use of stochastic X-ray pulses in two-dimensional spectroscopy to the simultaneous mapping of unoccupied and occupied electronic states of atoms in a regime where the opacity and transparency properties of matter are subject to the incident intensity and photon energy. A readily transferable matrix formalism is presented to extract the electronic states from a dataset measured with the monitored input from a stochastic excitation source. The presented formalism enables investigations of the response of the electronic structure to irradiation with intense X-ray pulses while the time structure of the incident pulses is preserved., Free electron X-ray laser pulses, generated by self-amplified spontaneous emission, are stochastic in nature. Here the authors present a reconstruction method for 2D spectroscopy while preserving the intrinsic properties of the incident pulses and apply it to a study towards X-ray intensity induced effects.

"Probe-before-destroy" methodology permitted diffraction and imaging measurements of intact specimens using ultrabright but highly destructive X-ray free-electron laser (XFEL) pulses. The methodology takes advantage of XFEL pulses ultrashort duration to outrun the destructive nature of the X-rays. Atomic movement, generally on the order of >50 fs, regulates the maximum pulse duration for intact specimen measurements. In this contribution, we report the electronic structure damage of a molecule with ultrashort X-ray pulses under preservation of the atoms' positions. A detailed investigation of the X-ray induced processes revealed that X-ray absorption events in the solvent produce a significant number of solvated electrons within attosecond and femtosecond timescales that are capable of coulombic interactions with the probed molecules. The presented findings show a strong influence on the experimental spectra coming from ionization of the probed atoms' surroundings leading to electronic structure modification much faster than direct absorption of photons. This work calls for consideration of this phenomenon in cases focused on samples embedded in, e.g., solutions or in matrices, which in fact concerns most of the experimental studies.

The electronic structure of phosphorus, sulfur, and chlorine in compounds with T_d and C_3v local symmetries was studied with high-resolution Kβ X-ray emission spectroscopy (XES) in the tender X-ray range. Measured spectra are compared to the results of ab initio quantum chemical calculations based on density functional theory (DFT). The spectral structure is reproduced by the model spectra of isolated XO^{; ; ; ; 4n–}; ; ; ; and XO^{; ; ; ; 3n–}; ; ; ; (X = P, S, or Cl) anions incorporating only the first coordination sphere around the central atom. The main spectral components can be explained by the molecular orbital theory. Finally, the potential of XES spectroscopy combined with DFT calculations to study the electronic structure of third-row elements in a slightly larger molecule is investigated.

Considerable effort has been devoted to the development of first-row transition-metal catalysts containing redox-active imino-pyridine ligands that are capable of storing multiple reducing equivalents. This property allows abundant and inexpensive first-row transition metals, which favor sequential one-electron redox processes, to function as competent catalysts in the concerted two-electron reduction of substrates. Herein we report the syntheses and characterization of a series of iron complexes that contain both π-donating thiolate and π-accepting (α-imino)-N-heterocycle redox-active ligands, with progressively larger N-heterocycle rings (imidazole, pyridine, and quinoline). A cooperative interaction between these complementary redox-active ligands is shown to dictate the properties of these complexes. Unusually intense charge-transfer (CT) bands, and intraligand metrical parameters, reminiscent of a reduced (α-imino)-N-heterocycle ligand (L(•−)), initially suggested that the electron-donating thiolate had reduced the N-heterocycle. Sulfur K-edge X-ray absorption spectroscopic (XAS) data, however, provides evidence for direct communication, via backbonding, between the thiolate sulfur and the formally orthogonal (α-imino)-N-heterocycle ligand π*-orbitals. DFT calculations provide evidence for extensive delocalization of bonds over the sulfur, iron, and (α-imino)-N-heterocycle, and TD-DFT shows that the intense optical CT bands involve transitions between a mixed Fe/S donor, and (α-imino)-N-heterocycle π*-acceptor orbital. The energies and intensities of the optical and S K-edge pre-edge XAS transitions are shown to correlate with N-heterocycle ring size, as do the redox potentials. When the thiolate is replaced with a thioether, or when the low-spin S = 0 Fe(II) is replaced with a high-spin S = 3/2 Co(II), the N-heterocycle ligand metrical parameters and electronic structure do not change relative to the neutral L(0) ligand. With respect to the development of future catalysts containing redox-active ligands, the energy cost of storing reducing equivalents is shown to be lowest when a quinoline, as opposed to imidazole or pyridine, is incorporated into the ligand backbone of the corresponding Fe complex.

An experimental and theoretical study of phosphorus electronic structure based on high energy resolution X-ray emission spectroscopy was performed. The Kα and Kβ emission spectra of several phosphorus compounds were recorded using monochromatic synchrotron radiation and megaelectronvolt (MeV) proton beam for target excitation. Measured spectra are compared to the results of ab initio quantum chemical calculations based on density functional theory (DFT). Clear correlation between energy position of the Kα emission line and the phosphorus formal oxidation state as well as DFT-calculated number of valence electrons is obtained ; measured energy shifts are reproduced by the calculations. Chemical sensitivity is increased further by looking at the Kβ emission spectra probing directly the structure of occupied molecular orbitals. Energies and relative intensities of main components are given together with the calculated average atomic character of the corresponding molecular orbitals involved in transitions.

The anticrossing structure of the $1s7l$ manifold of the helium atom in combined dc electric and magnetic fields is studied using a broadband photoexcitation with synchrotron light. The anticrossing signal is provided by the yield of atoms in the metastable $1s2s$ states to which the $1s7l$ states cascade. The mapping resolution depends solely on the homogeneity of the two fields in the target region, which is formed by the intersection of the synchrotron beam and the helium atom beam. The measured positions, as well as anticrossing intensities and widths, measured in the region of 1--1.5 kV/cm and 0--10 mT are in excellent agreement with the results of our extended theoretical simulations based on highly accurate zero-field wave functions. By centering the photoexcitation window to 65.110 and 65.130 eV, the same technique is applied to look for the anticrossings in the vicinity of the ${7}^{+}{\phantom{\rule{0.16em}{0ex}}}^{1}{P}_{1}^{o}--7d{\phantom{\rule{0.16em}{0ex}}}^{3}{D}_{1}^{o}$ and $7d{\phantom{\rule{0.16em}{0ex}}}^{1}{P}_{1}^{o}--{8}^{\ensuremath{-}}{\phantom{\rule{0.16em}{0ex}}}^{1}{P}_{1}^{o}$ pairs of doubly excited states, respectively.

International audience; A combination of resonant inelastic x-ray scattering and resonant Auger spectroscopy provides complementary information on the dynamic response of resonantly excited molecules. This is exemplified for CH3I, for which we reconstruct the potential energy surface of the dissociative I 3d−2 double-core-hole state and determine its lifetime. The proposed method holds a strong potential for monitoring the hard x-ray induced electron and nuclear dynamic response of core-excited molecules containing heavy elements, where ab initio calculations of potential energy surfaces and lifetimes remain challenging.

Kα X-ray emission spectra from a series of phosphorus, sulfur, and chlorine containing compounds covering the full range of oxidation states were measured employing high energy resolution proton induced X-ray emission (PIXE) spectroscopy in the tender X-ray range. Measurements were accompanied by quantum chemistry calculations based on density functional theory (DFT). Clear energy shifts of the Kα lines were measured in correlation with the formal oxidation state for all three elements. This correlation was improved even further using the effective charge based on the DFT calculated valence electron population. Finally, it is demonstrated that the oxidation state analysis based on the Kα energy shifts can be used also for a quantitative analysis of the proportion of separate low-Z species in mixed valence systems.

Application of new analytical tools providing insight into the mechanism of lithium– polysulfide formation in the cathode and their interaction with the host matrix and electrolyte is essential for further development of Li–S batteries. In this work, resonant inelastic X-ray scattering (RIXS) measurements at the sulfur K-edge were performed on the Li–S battery in operando mode to study the lithium-polysulfide formation during the discharge process. The relative amounts of each sulfur compound in the cathode during the discharge process were determined from the linear combination fit using reference spectra measured on standard sulfur compounds. Because of resonant excitation condition the sensitivity for the lithium–polysulfide detection was significantly enhanced, while the sulfate signal from the electrolyte was heavily suppressed. In addition, the influence of self- absorption effects in the analysis was minimized due to fixed excitation energy. Consequently, a full quantitative analysis could be performed for the conventional Li–S battery consisting of sulfur–carbon composite cathode free from any additives and a LiTFSI based electrolyte.

In this paper we report an X-ray emission study of bulk aqueous sulfuric acid. Throughout the range of molarities from 1 M to 18 M the sulfur Kβ emission spectra from H2SO4 (aq) depend on the molar fractions and related deprotonation of H2SO4. We compare the experimental results with results from emission spectrum calculations based on atomic structures of single molecules and structures from ab initio molecular dynamics simulations. We show that the S Kβ emission spectrum is a sensitive probe of the protonation state of the acid molecules. Using non-negative matrix factorization we are able to extract the fractions of different protonation states in the spectra and the results are in good agreement with the simulation for the higher part of the concentration range.

The effect of γ-radiation on a variety of model vitreous wasteforms applied to, or conceived for, immobilisation of UK intermediate and high level radioactive wastes was studied up to a dose of 8 MGy. It was determined that γ-irradiation up to this dose had no significant effect upon the mechanical properties of the wasteforms and there was no evidence of residual structural defects. FTIR and Raman spectroscopy showed no evidence of radiation directly affecting the silicate network of the glasses. The negligible impact of this γ-irradiation dose on the physical properties of the glass was attributed to the presence of multivalent ions, particularly Fe, and a mechanism by which the electron–hole pairs generated by γ-irradiation were annihilated by the Fe2+–Fe3+ redox mechanism. However, reduction of sulphur species in response to γ-radiation was demonstrated by S K-edge XANES and XES data.

Kβ X-ray spectra of chromium metal and selected chromium oxides were measured twice using medium resolution flat crystal spectrometer and high resolution spectrometer employing Johansson geometry after excitation with 2 MeV proton beams. The positions and intensities of crossover ( Kβ ″) and valence ( Kβ 2,5 ) band X-rays relative to the primary Kβ X-ray components were extracted in a consistent way. The results were compared with the existing data obtained by proton and photon induced ionization mechanisms and theoretical predictions. The obtained results in peak relative positions and intensities were analyzed in order to study dependence on the chromium oxidation states and chromium–oxygen bond lengths in selected chromium oxides. Our results obtained by both spectrometers confirm that the linear trend observed for the valence peak relative energy shift as a function of chromium oxidation number does not depend on the experimental resolution. Experimental results for normalized intensities (i.e. relative intensities divided with the number of chromium–oxygen pairs) of crossover and valence band X-rays obtained by both spectrometers are in very good agreement, and follow exponential relationship with the average Cr―O bond lengths in corresponding chromium oxides. The observed trends in crossover and valence X-rays normalized intensities could be used to measure the average chromium–oxygen bond length in various chromium oxides, with the sum of both crossover and valence X-ray normalized intensities being the most sensitive measure.

An X-ray spectroscopy and theoretical study of the chemical state of several sulfur bearing minerals and a synthetic sodium sulfite sample was performed. X-ray absorption and high-resolution Kα X-ray emission spectra were recorded and compared to ab initio quantum chemical calculations. A consistent interpretation of the chemical shift in the Kα emission spectra is obtained based on three different theoretical approaches (density functional theory, multiple scattering theory, and atomic multiplet theory). An analysis of the theoretical sulfur orbital population and valence bond is in agreement with the fluorescence energy position of the Kα lines even within the sulfide (S2−) series. It is shown that the Kα energy shifts can be used for a quantitative determination of the proportion of different sulfur species in heterogeneous samples.

In a previous work, it was shown that L shell X-ray yields relative to the Lα transition depend on the irradiation ion beam energy and the chemical species being irradiated [M.A. Reis, P.C. Chaves, J.C. Soares, Nucl. Instr. and Meth. B 239 (2005) 413]. Further studies give rise to the possibility that this dependence persists for transitions to the same sub-shell, where the ionization process is expected to play no role [P.C. Chaves, M.A. Reis, in: Milos Budnar, Matjaž Kavcic (Eds.), Proceedings (CD) of the Tenth International Conference on Particle Induced X-ray Emission and its Analytical Application, 4–8 June, Portorož – Slovenia, J. Stefan Institute, Ljubljana, 2004, p. 810]. In the present work, very high counting statistics (>4 × 106 counts in the peak) W–L spectra collected using a Si(Li) detector and Mo–L spectra obtained using the high resolution Johanson type crystal spectrometer from the Josef Stefan Institute were studied. In the case of Mo, an ultra pure Mo metal foil was used to avoid any possible target contamination and spectra were obtained for proton beam energies between 0.4 and 2.0 MeV. In the case of the W spectra, proton beam energies between 1.40 and 2.38 MeV were used. Normalizing to the theoretical yield ratios and plotting results as a function of the reduced velocity allows a single curve to be drawn for both cases. In this communication the results obtained are presented and discussed.

In this work our previous study about chemical effects in the Kα spectra of S compounds employing high-resolution X-ray spectroscopy has been extended to the Kβ emission spectra. The measurements were performed with a wavelength dispersive single crystal spectrometer operated in the von Hamos geometry having an energy resolution comparable to the natural linewidth of the measured Kβ X-ray lines. The target fluorescence was produced by irradiating the samples with the bremsstrahlung from an X-ray tube. The energies and widths of the main components in the Kβ emission spectrum are given for different sulfur compounds (sulfide, sulfite, sulfate). The measured energy shifts between the Kβ lines of the compounds and elemental sulfur are presented as a function of the sulfur oxidation state and compared with the results obtained from the former Kα measurements.

Introduction The influence of polyacetal wear particles on aseptic loosening of non-cemented isoelastic femoral stems with polyacetal coating remains unclear. The aim of our study was to use nuclear methods to prove the presence of polyacetal wear particles, to determine their morphology and to check their distribution in the tissues around loosend hip prosthetic components. Methods Tissue samples obtained during retrieval of 4 aseptic loosened primary hip prostheses with isoelastic stems made of polyacetal were subjected to nuclear analyses. Proton microbrobe method (mikro-PIXE) was used to prove the presence of polyacetal wear particles and to check for their morphology by detection of barium, which is molecularly in BaSO 4 embedded in polyacetal. Thermal neutron activation was used to determine distribution pattern of polyacetal wear in the peri-prosthetic tissues. Results Against expectations, polyacetal wear particles were found rather rare, larger than 100 µm and present in pseudo-membrane samples around the loosened stem, but virtual l y absent in tissues away from their origin. Concentration of BaSO 4 in polyacetal wear particles in pseudo-membrane samples was similar to the one in polyacetal coating (conc. Ba = 14217 µg/g and 14800 µg/g, respectively). Conclusion According to the results, the primary cause of the loosening of the isoelastic stems with polyacetal coating is most probably mechanical restlessness, which is responsible for local production of the large polyacetal wear particles responsible to accelerate the process of loosening. PIXE method and thermal neutron activation are sensitive quantitative nuclear methods suitable for direct or indirect detection of wear particles in the tissue around loosened prostheses and to determine morphology of wear particles and their distribution in the tissues.

Molybdenum oxides and sulfides were studied using resonant inelastic X-ray scattering (RIXS). The 2p(3/2)3d Mo RIXS planes show a rich structure with considerably more spectral information than in conventional X-ray absorption near edge structure (XANES) spectroscopy. The spectra were simulated using FEFF9 giving generally good agreement and detailed electronic information can be derived. The reference materials serve as a starting point for detailed electronic and geometric investigations of a broad range of compounds. In particular, this can provide insights in the properties and performance of unknown and changing materials like those in catalysis.

The aim of this study was to quantify the amount of the biologically active wear particles in the periprosthetic tissue around loosened polyacetal isoelastic stems to find the pattern of their distribution in the periprosthetic tissue and determine their origin. Proton microbeam measurements of thin tissue sections enabled us identification and quantified elemental analysis of individual wear particles in the tissue. The Ba concentration measured on the wear particles matches the Ba concentration measured with in-air PIXE on the polyacetal stem directly proving the origin of the wear particles which suppose to play a decisive biological role in the process of premature aseptic loosening of polyacetal stems.

A high-energy resolution crystal spectrometer in Johansson geometry, which allows energy resolution below the natural linewidth of the Ka diagram lines, was employed in the measurements of proton-induced Ka x-ray emission spectra of titanium and sulfur pure and compound targets. The results demonstrate a clear dependence of the Ka energy shifts on the chemical state of the element in the sample. This dependence permits the chemical state speciation of low-Z elements in an unknown sample by employing high-resolution PIXE measurements of the Ka line. The potential of the technique in speciation studies is demonstrated in the case of an aerosol sample. The analysis of the Ka line obtained from the high-energy resolution proton-induced S Ka x-ray spectrum allowed the identification of sulfur in the aerosol sample as sulfate ([SO 4 ] 2- ).

The proton induced Kα X-ray emission spectra of pure and some compound targets of sulfur were measured with a crystal spectrometer in Johansson geometry, which enables energy resolution below the natural linewidth of the measured Kα line. From these measurements the absolute energies of the S-Kα 1,2 lines were experimentally determined. In addition, the energies of the KαL 1 X-ray satellite lines, appearing in these spectra as a result of the radiative decay of atomic states with one hole in the K shell and one in the L subshells, were also measured. The measured Kα diagram and satellite line energies depend crucially on the S chemical state. The measured diagram line energies, as well as their relative intensity ratios obtained from the X-ray spectra of different S compounds, allow the deconvolution of X-ray spectra of mixed targets containing two different S compounds and the accurate determination of their mass ratio. Finally, the proton induced S-Kα X-ray spectrum from an aerosol sample was collected and the measured energies of the Kα 1,2 lines were used to specify the chemical state of S in the aerosol as a sulfate ([SO 4 ] 2− ). In conclusion, the results of the present paper demonstrate that the S-Kα 1,2 emission energies depend on the S chemical state and, therefore, their determination allows the chemical state speciation of S in a given sample.

Proton induced Kβ 1,3 X-ray spectra of mono-elemental targets of 3d transition elements (Ca, Ti, Cr) and chromium compounds (Cr 2 O 3 , K 2 CrO 4 , K 2 Cr 2 O 7 ) were measured by means of high-resolution crystal spectrometry. Kβ ′ line, Kβ 5 line, KβL 1 satellite line and the KMM radiative Auger contributions were clearly resolved and their energies and intensities relative to the parent diagram line determined. The influence of the oxidation state on the second order radiative contributions in emitted spectra of chromium compounds has been demonstrated and feasibility of its potential use for chemical state determination has been discussed.

The experimental database of the intensities of the KαL satellites induced in collisions with protons has been assembled. A detailed analysis of the rearrangement process and the influence of the L-shell spectator vacancy on the Kα fluorescence yield has been carried out, providing the ratios of the double to single ionization cross-section for the collected experimental points. These ratios were compared to the theoretical predictions within the independent particle model employing the semiclassical approximation (SCA). An empirical curve describing the ratio of the experimental and theoretical ionization probabilities has been deduced. This relationship can be used along with computed SCA values within PIXE data-processing packages such as GUPIX, to incorporate double ionization satellites into the model PIXE spectrum.

The paper presents the verification of home made Position Sensitive Spectrometer (PSS) while using synchrotron radiation light (SRL) as an excitation source. When Cr in the substance of light base was analyzed by the PSS, the lowest detection limit of a few ppm was achieved. Also linear proportionality between the count rate of the PSS and Cr concentration was obtained. This verities the feasibility of trace element analysis with high-energy resolution when using the PSS. At measurement of Cr Kβ5 band in metallic Cr and its compounds, it was discerned that the intensity of Cr Kβ5 becomes more intense with increasing oxidation number of Cr compounds. Such a change shows that high-energy resolution analysis using the PSS can make a useful method for the study of chemical states.

We report a theoretical and experimental study of the high resolution resonant K(α) X-ray emission lines around the chlorine K-edge in gas phase 1,1-dichloroethylene. With the help of ab initio electronic structure calculations and cross section evaluation, we interpret the lowest lying peak in the X-ray absorption and emission spectra. The behavior of the K(α) emission lines with respect to frequency detuning highlights the existence of femtosecond nuclear dynamics on the dissociative Potential Energy Surface of the first K-shell core-excited state.

photoexcitation spectra. Both two-electron excitation spectra are well described by a model spectrum builtofconsecutivebound-bounddiscretetransitionsandshake-upandshake-offchannelsgivingpreciseenergiesandintensitiesofthecorrespondingcontributions.Theobtainedresultsarecomparedwithotherexistingexperimentalvalues based on x-ray-absorption measurements and theoretical predictions.DOI: 10.1103/PhysRevA.90.022513 PACS number(s): 32

Seeded free electron lasers theoretically have the intensity, tunability, and resolution required for multiphoton spectroscopy of atomic and molecular species. Using the seeded free electron laser FERMI and a novel detection scheme, we have revealed the two-photon excitation spectra of dipole-forbidden doubly excited states in helium. The spectral profiles of the lowest (-1,0)^{+1} ^{1}S^{e} and (0,1)^{0} ^{1}D^{e} resonances display energy shifts in the meV range that depend on the pulse intensity. The results are explained by an effective two-level model based on calculated Rabi frequencies and decay rates.

Non-magnetic Pt catalysts, supported on carbon coated magnetic Co nanoparticles, changed catalytic performance in the presence of an external magnetic field. This behavior relates to an electronic change of Pt induced by a localized magnetic field, which modifies the CO adsorption geometry. In situ resonant inelastic X-ray scattering (RIXS) experiments and theory reveal the change of atop CO adsorption geometry on the Pt catalyst to bridged geometry under an external magnetic field. This observation opens the possibility of catalytic control by means of an external magnetic field.

We present a method suitable for the measurement of a high-energy resolved absorption spectrum in the emission mode upon target excitation with an intense monochromatic pulse of x-ray light. The approach is based on a measurement of a single resonant Raman x-ray spectrum at a fixed off-resonant excitation energy by a dispersive-type high-resolution emission spectrometer. Using a simple Lorentzian tail correction function and an energy-scale transformation, we reconstructed the ${L}_{3}$ absorption edge of Xe from the $3d$-$2{p}_{3/2}$ resonant Raman x-ray spectrum recorded at excitation energy 25 eV below the ${L}_{3}$ edge. The energy resolution is well below the ${L}_{3}$ core-hole lifetime broadening and allows for a straightforward extraction of the $[2{p}_{3/2}]n\ensuremath{\ell}$ resonance energies and emission strengths. The reconstructed spectrum is nearly equivalent to the high-energy resolution fluorescence detected absorption spectrum, which is recorded by scanning the photon excitation energy across the absorption edge.

Chlorine is a main elemental component of atmospheric particulate matter (APM). The knowledge of the chemical form of chlorine is of primary importance for source apportionment and for estimation of health effects of APM. In this work the applicability of high-resolution wavelength dispersive proton induced X-ray emission (PIXE) spectroscopy for chemical speciation of chlorine in fine fraction atmospheric aerosols is studied. A Johansson-type crystal spectrometer with energy resolution below the natural linewidth of Cl K lines was used to record the high-resolution Kα and Kβ proton induced spectra of several reference Cl compounds and two atmospheric aerosol samples, which were collected for conventional PIXE analysis. The Kα spectra which refers to the oxidation state, showed very minor differences due to the high electronegativity of Cl. However, the Kβ spectra exhibited pronounced chemical effects which were significant enough to perform chemical speciation. The major chlorine component in two fine fraction aerosol samples collected during a 2010 winter campaign in Budapest was clearly identified as NaCl by comparing the high-resolution Cl Kβ spectra from the aerosol samples with the corresponding reference spectra. This work demonstrates the feasibility of high-resolution PIXE method for chemical speciation of Cl in aerosols.

In the contribution the high-resolution X-ray spectrometer, originally constructed for the atomic physics research, is presented. Test measurements of Lβ and Lγ intensity ratios on In and Te compounds were performed. The applicability of the spectrometer for detection of chemical effects in X-ray spectra of compounds is discussed.

The basic purpose of the x-ray trace element analytical techniques is to detect with high sensitivity elemental constituents of the target (including elements in trace amounts) and determine quantitatively the elemental composition of the investigated sample. These techniques are based on the detection of x-rays following the atomic inner shell ionization. An inner shell (core) electron can be removed from the atom in different ways, for the analytical purposes x-ray absorption and proton scattering are most commonly used. In the case of X-Ray Fluorescence (XRF) method the x-ray tube is usually applied to irradiate the sample while in the case of Proton Induced X-ray Emission (PIXE) the proton beam accelerated by the electrostatic accelerator to typical energy of MeV is used to ionize the target atoms. The atom with a hole in the inner shell (core hole) is extremely unstable with characteristic lifetime in the order of 10-15 s. Consequently, the inner shell ionization is followed via subsequent x-ray or Auger electron emission. Both, PIXE and XRF method exploit the radiative decay channel. The energy of the emitted x rays is given by the energy difference of the electron states involved in the transition which is characteristic of the target element atomic number. In order to identify the elemental composition of the target, energy analysis of the emitted radiation is required with energy resolution high enough to resolve characteristic spectral contributions from different elements in the sample. Such resolution is achieved by the energy dispersive solid state detectors in which electric signals are proportional to the incident x-ray energy and they are commonly used in x-ray trace element analytical techniques. Besides good enough energy resolution they also provide an excellent efficiency, which is crucial to collect weak signals from trace elements in the sample. It was in fact the development of the semiconductor detectors in the seventies that has triggered the development of x-ray analytical techniques. Today both PIXE and XRF techniques being a multi-element, sensitive, fast, non destructive and relatively inexpensive, have established as a routine analytical tool in a variety of fields such as material analysis, environmental and biomedical research, archeological and art studies,... However, in some special cases the energy resolution of solid state energy dispersive detectors, nowadays reaching the order of 130 – 150 eV for the x-ray energies of few keV, is not enough and significantly higher energy resolution is required to enhance the analytical capabilities of the x-ray techniques. In order to increase further the energy resolution of x

We have measured a series of high-resolution x-ray spectra emitted upon resonant photoexcitation of HCl. The photon energy was tuned across the dissociative $1s\ensuremath{\rightarrow}6{\ensuremath{\sigma}}^{*}$ resonance and the Rydberg states converging to the Cl $1{s}^{\ensuremath{-}1}$ threshold, and inelastic photon scattering was observed in the region of KL emission lines. Excellent agreement is found between fully ab initio calculated and measured spectra if interferences between different excitation-emission paths are taken into account. The effect of electronic state interferences is enhanced due to dynamical broadening of the $6{\ensuremath{\sigma}}^{*}$ resonance in HCl.

The electronic structure and ligand environment of sulfur was investigated in various sulfur-containing compounds with different structures and chemical states by using X-ray emission spectroscopy (XES). Calculations were performed using density functional theory (DFT) as implemented in the StoBe code. The sulfur chemical state and atomic environment is discussed in terms of the molecular orbitals and partial charges that are obtained from the calculations. The main spectral features can be modeled using our calculational approach. The sensitivity of the Kbeta emission to the cation and the local symmetry is discussed.