L x‐ray fluorescence cross‐sections of heavy elements in the atomic region 57 ≤ Z ≤ 71 excited by 17.78 keV photons

L x‐ray fluorescence cross‐sections (σ_Lα, σ_Lβ, and σ_Lγ) were measured with an accuracy of 6% (except for the Lγ x‐ray line around 8%) for La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb and Lu at an excitation energy of 17.78 keV. Relative intensities I_Kβ/I_Kα and I_Lγ/I_Lα were also measured for the same elements. The measured cross‐sections were compared with experimental and theoretical values. Measurements of the emitted x‐rays were performed using an Si(Li) detector. Copyright © 2004 John Wiley & Sons, Ltd.     

Charge redistribution and a shortening of the Fe—As bond at the quantum critical point of SmO1–xFxFeAs

Many researchers have pointed out that there is a quantum critical point (QCP) in the F‐doped SmOFeAs system. In this paper, the electronic structure and local structure of the superconductive FeAs layer in SmO_1–xF_xFeAs as a function of the F‐doping concentration have been investigated using Fe and As K‐edge X‐ray absorption spectroscopy. Experiments performed on the X‐ray absorption near‐edge structure showed that in the vicinity of the QCP the intensity of the pre‐edge feature at the Fe‐edge decreases continuously, while there is a striking rise of the shoulder‐peak at the As edge, suggesting the occurrence of charge redistribution near the QCP. Further analysis on the As K‐edge extended X‐ray absorption fine structure demonstrated that the charge redistribution originates mostly from a shortening of the Fe—As bond at the QCP. An evident relationship between the mysterious QCP and the fundamental Fe—As bond was established, providing new insights on the interplay between QCP, charge dynamics and the local structural Fe—As bond in Fe‐based superconductors.     

A study of KαL1 X‐ray satellite spectrum of the elements 27 ≤ Z ≤ 31 by photon excitation

K _α X‐ray satellite spectra of Co, Ni, Cu, Zn, and Ga generated by photon excitation are analyzed using a wavelength dispersion spectrometer. Spectra of Ni, Cu, Zn, and Ga are studied for the first time using a LiF420 crystal. Spectrum of Co was studied with LiF200 crystal in second order. K_αL¹ X‐ray satellite energies and relative intensities are measured. The energy shifts relative to diagram line are computed and are compared with theoretical and semi‐empirical values. Dependence of energy shifts and relative intensities on Z and mode of excitation is analyzed.     

The density and tube energy dependency of cobalt Kα/Kβ in x‐ray fluorescence spectrometryfor thick target measurements

The relative intensity of K_α/K_β for cobalt in thick targets with cobalt mass densities from 0.51 to 22.49% has been measured by the wavelength dispersive x‐ray fluorescence (XRF) spectrometer. The measuring conditions are: tube current ranging from 10 to 60 mA and voltages ranging from 20 to 60 kV. We plotted the K_α/K_β ratio vs Co densities for different tube voltages and currents. Our study shows that the K_α/K_β ratio is below the theoretical value for low Co densities and it increases with increasing Co density. For higher x‐ray energies, the K_α/K_β ratio shows a sharp growth at the special density and then reaches a nearly constant value. However, K_α/K_β ratio is theoretically constant and independent of energy in thin target measurements. The changes of this ratio according to the x‐ray energy and the element density have been studied in thick target measurements. The results provide experimental evidence to suggest that exciting energy and element density can indeed affect the K_α/K_β ratio. Copyright © 2008 John Wiley & Sons, Ltd.     

Residual‐density mapping and site‐selective determination of anomalous scattering factors to examine the origin of the Fe K pre‐edge peak of magnetite

The electron‐density distribution and the contribution to anomalous scattering factors for Fe ions in magnetite have been analyzed by X‐ray resonant scattering at the pre‐edge of Fe K absorption. Synchrotron X‐ray experiments were carried out using a conventional four‐circle diffractometer in the right‐handed circular polarization. Difference‐Fourier synthesis was applied with a difference in structure factors measured on and off the pre‐edge (E_on = 7.1082 keV, E_off = 7.1051 keV). Electron‐density peaks due to X‐ray resonant scattering were clearly observed for both A and B sites. The real part of the anomalous scattering factor f′ has been determined site‐independently, based on the crystal‐structure refinements, to minimize the squared residuals at the Fe K pre‐edge. The f′ values obtained at E_on and E_off are ?7.063 and ?6.682 for the A site and ?6.971 and ?6.709 for the B site, which are significantly smaller than the values of ?6.206 and ?5.844, respectively, estimated from the Kramers–Kronig transform. The f′ values at E_on are reasonably smaller than those at E_off. Our results using a symmetry‐based consideration suggest that the origin of the pre‐edge peak is Fe ions occupying both A and B sites, where p–d mixing is needed with hybridized electrons of Fe in both sites overlapping the neighbouring O atoms.     

Measurements of L subshell and L shell x‐ray fluorescence cross‐sections for U and Th

The Ll, Lα_{1, 2}, Lη, Lβ₆, Lβ_{2, 4, 15, 17}, Lβ_{1, 3, 5}, Lβ_{9, 10}, Lγ₁, Lγ_{2, 3, 6, 8}, Lγ_4,4′ and Lγ₅ x‐ray fluorescence cross‐sections for U and Th were measured at 59.5 keV incident photon energy by using theoretical L_i subshell photoelectric cross‐sections, fluorescence and Coster–Kronig yields and fractional emission rates, and calculated theoretically by using atomic parameters. The measured values were compared with the theoretical values and experimental results available in the literature. Copyright © 2003 John Wiley & Sons, Ltd.     

Quantitative analysis of Mo–Si–B alloy phases with wavelength dispersive spectroscopy (WDS–SEM)

Mo–Si–B alloys show great potential as high temperature materials. Due to peak overlapping of B‐K_α and Mo‐M_ζ, analyzing these alloys with microanalysis presents a real challenge. This paper describes the analytical methodology used to qualify and quantify the boron content in these alloys without stoichiometric reference samples by the use of a single parallel‐beam wavelength dispersive spectrometer. Characterization of boron is performed by using a coupled energy dispersive X‐ray spectroscopy—wavelength dispersive spectroscopy system in a scanning electron microscope. Self‐made pure element samples are used for calibration and quantification of the boron content.     

Strikingly dissimilar effect of Mn and Zn dopants imposed on local structural distortion of Ba0.5K0.5Fe2As2 superconductor

To clarify the contrasting impurity effects of Mn and Zn dopants on the critical temperature of optimally doped Ba_0.5K_0.5Fe₂As₂ superconductors, extended X‐ray absorption fine‐structure spectroscopy was implemented at the Fe and As K‐edge. In Mn‐doped compounds a gradual deviation of the symmetric FeAs₄ tetrahedron and weakening of the Fe—As bond was observed. Conversely, in Zn‐doped compounds the perfect FeAs₄ tetrahedron is maintained and the Fe—As bond is rigid. The local structural details are consistent with the development of superconductivity in these two systems, suggesting a significant role played by the topology of the FeAs₄ tetrahedron and rigidness of the Fe—As bond in Mn/Zn‐doped Ba_0.5K_0.5Fe₂As₂ superconductors.     

Cascade Mi (i = 1–5) subshell X‐ray emission at incident photon energies across the Lj (j = 1–3) subshell absorption edges of 66Dy

The total M shell and the M_k (k = ξ, αβ, γ, m) X‐ray production cross sections for ₆₆Dy have been measured at incident photon energies across its L_j (j = 1–3) subshell absorption edge energies, ranging 7.8–9.2 keV. This study aims to investigate the evolution of the probability for cascade decay of L_j subshell vacancies as the tunable incident energy ionizes progressively different ₆₆Dy L_j subshells. The experimental X‐ray production cross sections have been compared with theoretical ones calculated using the nonrelativistic Hartree–Fock–Slater (HFS) model‐based photoionization cross sections; three sets of the X‐ray emission rates, fluorescence and Coster–Kronig yield based on the nonrelativistic Hartree–Slater (NRHS) model, Dirac–Hartree–Slater (DHS) model and Dirac–Fock (DF) model; the L_j (j = 1–3) subshell to the M_i (i = 1–5) subshell vacancy transfer probabilities evaluated in the present work. Presently measured total M shell and the M_αβ X‐ray production cross sections are found to be significantly lower than the theoretical ones evaluated using physical parameters based on the relativistic Dirac–Fock/Dirac–Hartree–Slater model calculations, whereas a much better agreement is observed with respect to the NRHS model‐based calculations; however, the measured X‐ray production cross sections are still systematically lower than the NRHS values.     

Study of absorption parameters around the K edge for selected compounds of Gd

The K shell absorption jump ratios, jump factors, effective atomic numbers, and electron densities were derived from the measured total mass attenuation coefficient using an energy dispersive X‐ray fluorescence spectrometer for Gd₂O₃, Gd₂(CO₃)₃H₂O, Gd₂(C₂O₄)₃H₂O, and Gd₂(SO₄)₃ compounds. The total mass attenuation coefficients were measured in the X‐ray energy range from 39.52 to 57.14 keV in a transmission geometry utilizing the Kα₂, Kα₁, Kβ₁, and Kβ₂ X‐rays from different secondary source targets excited by the 59.54‐keV photons from an Am‐241 annular source and detected by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. The energy gap, ionization energy, electron affinity, and global electrophilicity parameters of oxide, sulfate, oxalate, and carbonate ions were calculated using density functional theory (B3LYP). The experimental results are discussed based on these parameters. Copyright © 2015 John Wiley & Sons, Ltd.     

Three dimensional (Z‐dependence), collective and individual semi‐empirical formulae for L X‐ray production and ionization cross section by protons impact within corrected ECPSSR theory and updated experimental data: a review

In this paper we propose a new three dimensional semi‐empirical formulae for the deduction of L X‐ray production and ionization cross sections by introducing the dependence on the atomic number of the target, noted as ‘Z‐dependence’. The data are also fitted collectively and separately (for each element) by analytical functions to calculate semi‐empirical cross sections. For this purpose, the corrected ECPSSR model (noted as eCPSSR) and the published experimental data of L_α, L_β and L_γ X‐ray production and L₁, L₂ and L₃ ionization cross sections in the period (1950–2014) are combined to calculate the semi‐empirical ones for a wide range of elements by proton impact. The semi‐empirical cross sections (for the three x‐rays lines L_α, L_β, L_γ and the three sub‐shells L₁, L₂, L₃) are then deduced by fitting the available experimental data normalized to their corresponding theoretical values (using the eCPSSR model) giving a better representation of the experimental data for the individual interpolation. At last, a comparison is made between the three semi‐empirical formulae reported in this work. Copyright © 2016 John Wiley & Sons, Ltd.     

Methodology for the characterisation of characteristic spectral profiles,applied to chromium Kβ

The investigation of tests of quantum electrodynamics in the X‐ray regime down to 2–20 parts per million (ppm) amplifies the need for improved characterisation of asymmetric reference sources and energies in this regime. While several transition metal characteristic energies have been defined, most are not referenced to accurate profiles or robust links to the metre via X‐ray optical interferometry. Lower intensity Kβ transitions have relatively poor accuracy – we ask how to determine Kβ transitions to an accuracy approaching those of Kα transitions. Instrumental broadening normally encountered in X‐ray experiments shifts the features of profiles used for calibration, such as peak energy, by a significant amount many times the quoted accuracies. We present a study of a methodology used recently to determine energies and profiles experimentally down to 4.5 and 2.7 ppm for Ti and V Kβ. In this study, we investigate the robustness of the methodology for a difficult data set and demonstrate that the approaches to and characterisation of the chromium Kβ spectral profile are consistent with accurate measurements in the literature down to 24 ppm. The peak energy of the chromium Kβ spectral profile is found to be 5946.68(14) eV prior to instrumental broadening. Characterisation of the spectral profile of the radiation, including the instrumental broadening, allows us to obtain an accurate and notably transferable standard. Significantly, we present a widely applicable methodology for achieving and using this standard. This approach has been used down to an accuracy of 2–5 ppm.     

X‐ray fluorescence determination of sulfur chemical state in sulfide ores

This paper describes the X‐ray fluorescence technique for estimation of the ratio between sulfide and total sulfur in sulfide ores using the influence of sulfur chemical state on positions and intensities of lines (SKα_1,2, SKβ_1,3) and satellites (SKβ′, SKα_3,4) of the sulfur X‐ray emission spectra measured by the wavelength‐dispersive X‐ray fluorescence spectrometer. The samples to be analyzed were prepared as pressed powder pellets on boric acid substrate. The SKα_1,2 line chemical shift is the most appropriate parameter for sulfur chemical state estimation because spectral lines in this field are intensive and are almost not affected by spectral overlap of lead spectrum lines. The ratios of line intensities SKβ′/SKβ_1,3, SKα_3,4/SKα_1,2 and SKβ_1,3/SKα_1,2 were also used as analytical parameters. Forty‐one samples of sulfide ores collected in the Russian Far East and Southern Ural deposits have been analyzed. The results of estimation of sulfur chemical state by gravimetric and proposed X‐ray fluorescence techniques agree fairly well. Copyright © 2016 John Wiley & Sons, Ltd.     

Study of fossil bones by synchrotron radiation micro‐spectroscopic techniques and scanning electron microscopy

Earlymost Villafranchian fossil bones of an artiodactyl and a perissodactyl from the Milia excavation site in Grevena, Greece, were studied in order to evaluate diagenetic effects. Optical microscopy revealed the different bone types (fibro‐lamellar and Haversian, respectively) of the two fragments and their good preservation state. The spatial distribution of bone apatite and soil‐originating elements was studied using micro‐X‐ray fluorescence (µ‐XRF) mapping and scanning electron microscopy. The approximate value of the Ca/P ratio was 2.2, as determined from scanning electron microscopy measurements. Bacterial boring was detected close to the periosteal region and Fe bearing oxides were found to fill bone cavities, e.g. Haversian canals and osteocyte lacunae. In the perissodactyl bone considerable amounts of Mn were detected close to cracks (the Mn/Fe weight ratio takes values up to 3.5). Goethite and pyrite were detected in both samples by means of metallographic microscopy. The local Ca/P ratio determined with µ‐XRF varied significantly in metal‐poor spots indicating spatial inhomogeneities in the ionic substitutions. XRF line scans that span the bone cross sections revealed that Fe and Mn contaminate the bones from both the periosteum and medullar cavity and aggregate around local maxima. The formation of goethite, irrespective of the local Fe concentration, was verified by the Fe K‐edge X‐ray absorption fine structure (XAFS) spectra. Finally, Sr K‐edge extended XAFS (EXAFS) revealed that Sr substitutes for Ca in bone apatite without obvious preference to the Ca₁ or Ca₂ unit‐cell site occupation.     

Experimental L x‐ray fluorescence cross‐sections for elements with 45 ≤ Z ≤ 50 at 7 keV by synchrotron radiation photoionization

L x‐ray fluorescence cross‐sections for elements with 45 ≤ Z ≤ 50 were measured at 7 keV using synchrotron radiation photoionization. The experimental set‐up provided a linearly polarized monoenergetic photon beam producing a low background and improving the signal‐to‐noise ratio. The data obtained for the L lines, Ll, Lα, Lβ_I, Lβ_II, Lγ_I and Lγ_II, were grouped considering the transition scheme, the energies of the emission lines and the detector resolution. Results for the experimental cross‐sections obtained were compared with theoretical values using two different data tables. In general, it was found that the experimental fluorescence cross‐sections are slightly higher (7–10%) than the theoretically calculated data and in some cases these differences are up to 40%. Copyright © 2005 John Wiley & Sons, Ltd.     

Synchrotron radiation induced X‐ray production cross sections of 66Dy at energies across its Li (i = 1–3) subshell absorption edges

The X‐ray production (XRP) cross sections for the ₆₆Dy L_k (k = l, α, η, β_2,6,7,15, β_1,6, β_1,3,4,6, β_2,7,15, γ_1,5, γ₂,₃) emission lines have been measured by tuning the incident synchrotron radiation at energies over the range 7.8–9.2 keV and ~10–370 eV above the respective L_i (i = 1–3) absorption edges. These measurements aim to check the reliability of the independent particle approximation models used to generate the theoretical data sets of different physical parameters required to calculate the XRP cross sections and also investigate the influence of many body effects on the photoionization process. The measured values have been compared with 4 sets of XRP cross sections calculated using the Dirac–Fock model‐based X‐ray emission rates, 2 sets of the L_i (i = 1–3) subshell photoionization cross sections deduced from the self‐consistent Dirac–Hartree–Fock model‐based values and the nonrelativistic Hartree–Fock–Slater model‐based values, and 2 sets of the fluorescence (ω_i) and Coster–Kronig (f_ij) yields. The present measured Lγ_2,3 (originating from decay of the L₁ subshell vacancies) XRP cross sections are found to be significantly higher than different sets of theoretical values, whereas a good agreement is generally observed for the various other XRP cross sections and relative intensities.     

Physical parameters for atomic inner‐shell photoionization processes and analytical applications: a status report

The atomic inner‐shell vacancy decay processes comprising of radiative and non‐radiative transitions are characterized by the physical parameters, namely, the photoionization cross‐sections; X‐ray, Auger and Coster–Kronig (CK) transition rates; fluorescence and CK yields; and the vacancy transfer probabilities. These parameters are required to calculate the K‐shell and L_i (i = 1–3)/M_i (i = 1–5) sub‐shell X‐ray production cross‐sections and relative intensities which, in turn, are needed for different analytical applications. This report intended to provide a detailed account of the currently available data sets of different physical parameters for use in various analytical applications. Copyright © 2011 John Wiley & Sons, Ltd.     

X‐ray spectroscopy for chemistry in the 2‐4 keV energy regime at the XMaS beamline: ionic liquids,Rh and Pd catalysts in gas and liquid environments,and Cl contamination in γ‐Al2O3

The 2–4 keV energy range provides a rich window into many facets of materials science and chemistry. Within this window, P, S, Cl, K and Ca K‐edges may be found along with the L‐edges of industrially important elements from Y through to Sn. Yet, compared with those that cater for energies above ca. 4–5 keV, there are relatively few resources available for X‐ray spectroscopy below these energies. In addition, in situ or operando studies become to varying degrees more challenging than at higher X‐ray energies due to restrictions imposed by the lower energies of the X‐rays upon the design and construction of appropriate sample environments. The XMaS beamline at the ESRF has recently made efforts to extend its operational energy range to include this softer end of the X‐ray spectrum. In this report the resulting performance of this resource for X‐ray spectroscopy is detailed with specific attention drawn to: understanding electrostatic and charge transfer effects at the S K‐edge in ionic liquids; quantification of dilution limits at the Cl K‐ and Rh L₃‐edges and structural equilibria in solution; in vacuum deposition and reduction of [Rh^I(CO)₂Cl]₂ to γ‐Al₂O₃; contamination of γ‐Al₂O₃ by Cl and its potential role in determining the chemical character of supported Rh catalysts; and the development of chlorinated Pd catalysts in `green' solvent systems. Sample environments thus far developed are also presented, characterized and their overall performance evaluated.     

Instrumental detection limit and sensitivity of K and L shell X‐ray emission lines of 17Cl, 37Rb,and 38Sr elements using PC‐WDXRF spectrometer

This work was aimed to improve the instrumental detection limit and sensitivity of ₁₇Cl, ₃₇Rb, and ₃₈Sr elements present in solid samples by using the advanced polychromatic wavelength dispersive X‐ray fluorescence spectrometry method. Instrumental measuring parameters, as well as study of calibration curves of K and L shell spectral lines, were evaluated to select the best conditions for ₁₇Cl, ₃₇Rb, and ₃₈Sr quantification. From the results, it was observed that the detection limits of the Rb Kα and Sr Kα spectral lines were lower than those of the Kβ_1,3 and Lα spectral lines. From the calibration curves, it was concluded that Kα spectral lines are more suitable than Kβ_1,3 and Lα lines to identify the traces of ₁₇Cl, ₃₇Rb, and ₃₈Sr elements in different types of solid samples.