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The design and performance of a high-resolution transmission-type X-ray spectrometer for use in the 15–26 keV energy range at synchrotron light sources is reported. Monte Carlo X-ray-tracing simulations were performed to optimize the performance of the transmission-type spectrometer, based on the DuMond geometry, for use at the Super X-ray absorption beamline of the Swiss Light Source at the Paul Scherrer Institute. This spectrometer provides an instrumental energy resolution of 3.5 eV for X-ray emission lines around 16 keV and 12.5 eV for emission lines at 26 keV, which is comparable to the natural linewidths of the K and L X-ray transitions in the covered energy range. First experimental data are presented and compared with results of the Monte Carlo X-ray simulations.

We report on the radiative decay of double K-shell vacancy states produced in solid Ca, V, Fe, and Cu targets by impact with about 10 MeV/amu C and Ne ions. The resulting K hypersatellite x-ray emission spectra were measured by means of high- energy-resolution spectroscopy using a von Hamos bent crystal spectrometer. The experiment was carried out at the Philips variable energy cyclotron of the Paul Scherrer Institute. From the fits of the x-ray spectra the energies, line widths, and relative intensities of the hypersatellite x-ray lines could be determined. The fitted intensities were corrected to account for the energy-dependent solid angle of the spectrometer, effective source size, target self-absorption, crystal reflectivity, and detector efficiency. The single-to-double K-shell ionization cross-section ratios were deduced from the corrected relative intensities of the hypersatellites and compared to theoretical predictions from the semiclassical approximation model using hydrogenlike and Dirac-Hartree-Fock wave functions and from classical trajectory Monte Carlo calculations.

We report on the investigation of the photon energy dependence of double 1s photoionization of light atoms and compare the cross sections for hollow atom and He-like ion production. Measurements of the Kα hypersatellite x-ray spectra of Mg, Al, and Si were carried out using the Fribourg high-resolution x-ray spectrometer installed at the ID21 and ID26 beam lines at the ESRF. The double-to-single photoionization cross section ratios were derived as a function of the incident photon beam energy and compared to convergent close-coupling (CCC) calculations for He-like ions. The dynamical electron-electron scattering contribution to the DPI cross-sections was found to be more important for neutral atoms than for the He isoelectronic series.

X-ray atomic properties of Nickel were investigated in a singular approach that combines different experimental techniques to obtain new and useful reliable values of atomic fundamental parameters for X-ray spectrometric purposes and for comparison to theoretical predictions. We determined the mass attenuation coefficients in an energy range covering the L- and K- absorption edges, the K-shell fluorescence yield and the Kb/Ka and Kb1,3/Ka1,2 transition probability ratios. The obtained line profiles and linewidths of the Ka and Kb transitions in Ni can be considered as the contribution of the satellite lines arising from the [KM] shake processes suggested by Deutsch et al. [1] and Ito et al. [2]. Comparison of the new data with several databases showed a good agreement but also discrepancies were found with existing tabulated values.

In the present work high energy resolution off-resonant X-ray spectroscopy (HEROS) was employed at a synchrotron to study a silica supported Ta(V) bisalkyl catalyst activated in hydrogen. The Ta Lα1 HEROS spectra were measured during oxidation of the starting complex and the relative species’ concentration was successfully retrieved as a function of time using the fingerprint HEROS spectra measured for the unoxidized and the oxidized catalyst. Based on the experimental data and theory- based calculations, it was shown that oxidation of the active Ta catalyst leads to the formation of mono- and di-meric species on the SiO2 surface. The obtained results were compared to those of the previously reported time-resolved HEROS study on an inactive silica supported Ta(V) bisalkyl catalyst’s concentration evolution during its oxidation Błachucki et al. (2015). The study allowed observation of an immediate transition of the active Ta catalyst from its unoxidized form to the oxidized one. This finding is dissimilar to the result of the study on the inactive Ta catalyst, where the oxidation led through an intermediate step.

The potential of valence to core Al X-ray emission spectroscopy to determine aluminum distribution in ferrierite zeolites was investigated. The recorded emission spectra of four samples prepared with different structure directing agents exhibit slight variations in the position of the main emission peak and the intensity of its low energy shoulder. Theoretical calculations indicate that an increased intensity of the Kβx shoulder in the Al emission spectra can be linked to a predominant occupation of the T3 site by a single aluminum atom. This study thus suggests that valence to core X- ray emission spectroscopy can be applied to help determine the occupation of aluminum at crystallographic T-sites in zeolites.

Single-photon double K-shell ionization of low-Z neutral atoms in the range 12⩽Z⩽23 is investigated. The experimental method was based on measurements of the high- resolution Kαh hypersatellite x-ray spectra following the radiative decay of the K-shell double-vacancy states excited by monochromatic synchrotron radiation. The photon energy dependence of the double K-shell ionization was measured over a wide range of photon energies from threshold up to and beyond the maximum of the double-to- single photoionization cross section ratios. From the high-resolution x-ray emission spectra the energies and linewidths of the hypersatellite transitions, as well as the Kαh1:Kαh2 intensity ratios, were determined. The relative importance of the initial-state and final-state electron-electron interactions to the K-shell double photoionization is addressed. Physical mechanisms and scaling laws of the K-shell double photoionization are examined. A semiempirical universal scaling of the double- photoionization cross sections with the effective nuclear charge for neutral atoms in the range 2⩽Z⩽47 is established.

We report on nonlinear interaction of solid Fe with intense femtosecond hard x-ray free-electron laser (XFEL) pulses. The experiment was performed at the CXI end- station of the Linac Coherent Light Source (LCLS) by means of high- resolution x-ray emission spectroscopy. The focused x-ray beam provided extreme fluence of ~10⁵ photons/Ų. Two-photon absorption leading to K-shell hollow atom formation and to single K-shell ionization of solid Fe was investigated.

Fluorescence yields (FYs) for the Ge L shell were determined by a theoretical and two experimental groups within the framework of the International Initiative on X-Ray Fundamental Parameters Collaboration. Calculations were performed using the Dirac-Fock method, including relativistic and QED corrections. The experimental value of the L3FYωL3 was determined at the Physikalisch-Technische Bundesanstalt undulator beamline of the synchrotron radiation facility BESSY II in Berlin, Germany, and the Lα1,2 and Lβ1 line widths were measured at the Swiss Light Source, Paul Scherrer Institute, Switzerland, using monochromatized synchrotron radiation and a von Hamos x-ray crystal spectrometer. The measured fluorescence yields and line widths are compared to the corresponding calculated values.

We report on the reactivity of grafted tantalum organometallic catalysts with molecular oxygen. The changes in the local Ta electronic structure were followed by in situ high-energy resolution off-resonant spectroscopy (HEROS). The results revealed agglomeration and formation of Ta dimers, which cannot be reversed. The process occurs independently of starting grafted complex.

The grazing emission X-ray fluorescence (GEXRF) technique was applied to the analysis of different Al films, with nominal thicknesses in the range of 1 nm to 150 nm, on Si wafers. In GEXRF the sample volume from which the fluorescence intensity is detected is restricted to a near-surface region whose thickness can be tuned by varying the observation angle. This is possible because of the refraction of the fluorescence X-rays and the quite long emission paths within the probed sample. By recording the X-ray fluorescence signal for different shallow emission angles, defined relatively to the flat, smooth sample surface, the deposited Al surface layers of the different samples could be well characterized in terms of layer thickness, layer density, oxidation and surface roughness. The advantages offered by synchrotron radiation and the employed wavelength-dispersive detection setup were profited from. The GEXRF results retrieved were confirmed by complementary measurements. The experimental setup, the principles and advantages of GEXRF and the analysis of the recorded angular intensity profiles will be discussed in details.

High-energy-resolution photoexcited KN2,3 x-ray-emission measurements were carried out on krypton with the excitation energy tuned around the 1s4p and 1s3d double-excitation thresholds. Comprehensive two-dimensional resonant inelastic x-ray-scattering maps were recorded for the range of excitation and emission energies corresponding to both types of double excitations. The double-excitation signal could be clearly resolved from the dominant 1s ionization signal. The latter was subtracted from the measured maps, yielding isolated 1s4p and 1s3d photoexcitation spectra. Both two-electron excitation spectra are well described by a model spectrum built of consecutive bound-bound discrete transitions and shake-up and shake-off channels giving precise energies and intensities of the corresponding contributions. The obtained results are compared with other existing experimental values based on x-ray-absorption measurements and theoretical predictions.

X-ray emission spectra recorded in the off-resonant regime carry information on the density of unoccupied states. It is known that by employing the Kramers-Heisenberg formalism, the high energy resolution off-resonant spectroscopy (HEROS) is equivalent to the x-ray absorption spectroscopy (XAS) technique and provides the same electronic state information. Moreover, in the present Letter we demonstrate that the shape of HEROS spectra is not modified by self-absorption effects. Therefore, in contrast to the fluorescence-based XAS techniques, the recorded shape of the spectra is independent of the sample concentration or thickness. The HEROS may thus be used as an experimental technique when precise information about specific absorption features and their strengths is crucial for chemical speciation or theoretical evaluation.

A detailed investigation of the Lα1,2 (L3→M4,5) and Lβ1 (L2→M4) x-ray satellite and hypersatellite structures in zirconium, molybdenum, and palladium atoms multiply ionized by impact with 278.6-MeV oxygen ions is reported. The x-ray spectra were measured with a high-resolution von Hamos bent crystal spectrometer. For the interpretation of the complex spectral features, relativistic multiconfiguration Dirac-Fock calculations were performed for all multivacancy configurations expected to contribute to the observed spectra. The data analysis clearly demonstrates that the spectra are dominated by structures originating from (L−1M−mN−n) satellite and (L−2M−mN−n) hypersatellite transitions corresponding to the radiative decay of the excited multivacancy configurations. The ionization probabilities of the L and M shell were determined from the data and compared with theoretical predictions from the geometrical model and the semiclassical approximation, using in the latter case both relativistic hydrogenlike and self-consistent Dirac-Hartree-Fock wave functions. The results support the independent electron picture of the multiple ionization. They also show the importance of using relativistic and self-consistent electronic wave functions for the L and M shells.

We report on high-resolution measurements of the photoinduced L1M2 and L1M3 x-ray emission lines of 69Tm, 70Yb, 71Lu, 73Ta, 74W, 75Re, 77Ir, 81Tl, 83Bi, and 95Am. From the linewidths of the measured transitions an accurate set of M2 and M3 level widths is determined assuming for the L1 level widths the values reported by Raboud [P.-A. Raboud et al., Phys. Rev. A 65, 022512 (2002)]. Furthermore, the present experimental M2,3 data set is extended to 80Hg, 90Th, and 92U, using former L1M2,3 high-resolution x-ray emission spectroscopy measurements performed by our group. A detailed comparison of the M2 and M3 level widths determined in the present work with those recommended by Campbell and Papp [J. L. Campbell and T. Papp, At. Data Nucl. Data Tables 77, 1 (2001)] and other available experimental data as well as theoretical predictions is done. The observed abrupt changes of the M2,3 level widths versus atomic number Z can be explained satisfactorily by the cutoffs and onsets of the M2M4N1, respectively M3M4N3,4,5 and M3M5N2,3 Coster-Kronig transitions deduced from the semiempirical (Z+1) approximation. As a spin-off result of this study, precise L1M2 and L1M3 transition energies are obtained for the investigated elements. A very good agreement with transition energies calculated within the many-body perturbation theory is found.

We report on the surface-sensitive grazing emission X-ray fluorescence technique combined with synchrotron radiation excitation and high-resolution detection to realize depth-profile measurements of Al-implanted Si wafers. The principles of grazing emission measurements as well as the benefits offered by synchrotron sources and wavelength-dispersive detection setups are presented. It is shown that the depth distribution of implanted ions can be extracted from the dependence of the X-ray fluorescence intensity on the grazing emission angle with nanometer-scale precision provided that an analytical function describing the shape of the depth distribution is assumed beforehand. If no a priori assumption is made, except a bell shaped form for the dopant distribution, the profile derived from the measured angular distribution is found to reproduce quite satisfactorily the depth distribution of the implanted ions.

We propose a novel approach for the theoretical analysis of the photoinduced high-resolution Khα1,2 x-ray hypersatellite spectra, which allows us to obtain reliable values of lifetimes of the doubly K-shell ionized states and fundamental information about the relative role of K-shell double photoionization (DPI) mechanisms. It is demonstrated for the first time that the Khα1,2 hypersatellite natural line broadening observed for selected metal atoms with 20≤Z≤30 can be well reproduced quantitatively by taking into account the influences of the open-shell valence configuration (adopted from predictions of the band-structure method) and the outer-shell ionization and excitation following the DPI process.

xperimental evidence for the correlated two-electron one-photon transitions (1s⁻²→2s⁻¹2p⁻¹) following single-photon K-shell double ionization is reported. The double K-shell vacancy states in solid Mg, Al, and Si were produced by means of monochromatized synchrotron radiation, and the two-electron one-photon radiative transitions were observed by using a wavelength dispersive spectrometer. The two-electron one-photon transition energies and the branching ratios of the radiative one-electron to two-electron transitions were determined and compared to available perturbation theory predictions and configuration interaction calculations.

The KMM radiative Auger (RA) x-ray spectra of solid Ca were induced by monochromatic synchrotron radiation and measured with a high-resolution von Hamos bent crystal spectrometer. Two excitation energies were employed, one in the near K threshold region and the second well above the K absorption edge. The KMM RA spectral structure and relative intensity with respect to the diagram Kβ1,3 (K-M3,2) line are found to be independent of the excitation energy. The overall RA structure resembles the density of unoccupied s, p, and d states. Due to solid-state effects, however, spectral features resulting from the major discrete shake-up transitions could not be resolved. For the total KMM RA to Kβ1,3 yield ratio, a value of 0.053(3) is obtained. The latter is compared to theoretical predictions and available experimental data obtained by various types of target excitation.

The electron-induced L₃M two-step double ionization cross sections of metallic Pd were determined experimentally for incident electron beam energies ranging from the double ionization threshold up to 18 keV. The double L₃M ionization cross sections were derived from the intensity ratios (ILαM:ILα) of the resolved M satellites to the parent diagram lines. The sample was bombarded with monoenergetic electrons from an energy-tunable 20-kV electron gun. The diagram and M-satellite x-ray lines were measured by means of high-resolution x-ray spectroscopy, using a reflection-type von Hamos bent crystal spectrometer. The two-step partial cross sections were determined by subtracting from the measured total double ionization cross sections the contributions due to the shake process and L₁-L₃M4,5 Coster-Kronig transitions. Despite the thick target employed in the present study, the dependence of the two-step cross sections on the incoming electron energy could be derived using a target slice decomposition method. It is shown that the obtained energy dependence can be well reproduced by the semiempirical parametrization model of Pattard and Rost.

An observation of the internal structure of the L-shell hypersatellite x rays resulting from the one-photon decay of L⁻² double-vacancy states in palladium multiply ionized by oxygen ions is reported. The Pd L₃→M4,5 x-ray spectrum was measured with a von Hamos high-resolution crystal spectrometer. The complex shape of the observed spectrum could be interpreted in detail using relativistic multiconfiguration Dirac-Fock calculations. The relative intensities of the measured x rays were found to be in good agreement with semiclassical approximation calculations using relativistic Dirac-Hartree-Fock wave functions.

The development of a wavelength-dispersive spectrometer for microfluorescence analysis at the X-ray Microscopy ID21 beamline of the European Synchrotron Radiation Facility (ESRF) is reported. The spectrometer is based on a polycapillary optic for X-ray fluorescence collection and is operated in a flat-crystal geometry. The design considerations as well as operation characteristics of the spectrometer are presented. The achieved performances, in particular the energy resolution, are compared with the results of Monte Carlo simulations. Further improvement in the energy resolution, down to ~eV range, by employing a double-crystal geometry is examined. Finally, examples of applications requiring both spatial and spectral resolutions are presented.

The synchrotron radiation based high-resolution grazing emission X-ray fluorescence (GEXRF) technique was used to extract the distribution of Al ions implanted with a dose of 10¹⁶ atoms/cm² in Si wafers with energies ranging between 1 and 100 keV. The depth distributions of the implanted ions were deduced from the measured angular profiles of the Al-Kα X-ray fluorescence line with nanometer-scale precision. The experimental results were compared to theoretical predictions of the depth distributions resulting from ion implantation. A good agreement between experiment and theory was found which proved that the presented high-resolution grazing emission X-ray fluorescence technique is well suited to perform depth profiling measurements of impurities located within the extinction depth, provided the overall shape of the distribution can be assumed a priori.

The interpretation of L-shell satellites and hypersatellites for Lα1,2 (L₃→M4,5) and Lβ₁ (L₂→M₄) x-ray transitions in zirconium multiply ionized by oxygen and neon ions is reported. The x-ray spectra were measured with a high-resolution von Hamos spectrometer and interpreted in terms the relativistic multi-configuration Dirac-Fock (MCDF) calculations. The ionization probabilities of L- and M-shell derived from the data are compared with the predictions of the semiclassical approximation (SCA) calculations.

The xenon L-subshell Coster-Kronig (CK) transition yields were revisited via high-resolution measurements of the Lα1,2 (L₃-M4,5) and Lβ₁ (L₂-M₄) x-ray emission lines. The L x-ray spectra were measured employing a Johansson-type curved crystal spectrometer and energy-tunable synchrotron radiation. The CK yields were derived from the relative L x-ray intensity jumps at the L edges by fitting the fluorescence intensities as a function of the photon energy to the L-subshell photoionization cross sections. The latter were obtained from the measured L-edge photoabsorption spectrum. Values of 0.118±0.029, 0.383±0.037, and 0.096±0.016 were found for the f₂₃, f₁₃, and f₁₂ CK yields, respectively. Thanks to high resolution, the L₁ fluorescence yield of 0.059±0.002 was also determined from intensity ratios of the well-resolved Lβ₄ (L₁-M₂) and Lβ₁ (L₂-M₄) lines.