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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.

Physical review / A 107(1), 013113 (2023). doi:10.1103/PhysRevA.107.013113, We present the results of a theoretical study of XUV superfluorescence from doubly excited states of helium resonantly pumped by free-electron laser (FEL) pulses. Our model allows us to predict both the spectrum and angular distribution of emitted XUV radiation in a wide range of experimentally accessible parameters. This is achieved by going beyond two key deficiencies of most previous models: The one-dimensional treatment in space is upgraded to three dimensions with electromagnetic fields treated in the paraxial approximation and spontaneous emission is modeled by a recently developed approach that avoids the unrealistic delayed response but preserves the expected characteristics of the emitted field in the spontaneous emission limit. The case study of 3a$^1$P$^o$ resonance in helium with 63.66 eV excitation energy is presented for realistic parameters of seeded light pulses from the FERMI FEL facility and a recently developed high-pressure gas cell. Results of numerical simulations show that both the spectral width and angular divergence of emitted radiation vary with gas pressure and pump pulse intensity in a complex way., Published by Inst., Woodbury, NY

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

Human hair absorbs numerous biomolecules from the body during its growth. This can act as a fingerprint to determine substance intake of an individual, which can be useful in forensic studies. The cocaine concentration profile along the growth axis of hair indicates the time evolution of the metabolic incorporation of cocaine usage. It could be either assessed by chemical extraction and further analysis of hair bundels, or by direct single hair fibre analysis with mass spectroscopy imaging (MSI). Within this work, we analyzed the cocaine distribution in individual hair samples using MeV-SIMS. Unlike conventional surface analysis methods, we demonstrate high yields of nonfragmented molecular ions from the surface of biological materials, resulting in high chemical sensitivity and non-destructive characterisation. Hair samples were prepared by longitudinally cutting along the axis of growth, leaving half-cylindrical shape to access the interior structure of the hair by the probing ion beam, and attached to the silicon wafer. A focused 5.8 MeV 35Cl6+ beam was scanned across the intact, chemically pristine hair structure. A non-fragmented protonated [M+ H]+ cocaine molecular peak at m/z = 304 was detected and localized along the cross-section of the hair. Its intensity exhibits strong fluctuations along the direction of the hair’s growth, with pronounced peaks as narrow as 50 micrometres, corresponding to a metabolic incorporation time of approx. three hours.

We report an electron scattering experiment on argon gas where a keV electron beam is used as a probe and electrons are collected with a magnetic bottle spectrometer. For this purpose, we have built a thermionic gun that produces electron pulses with nanosecond duration by sweeping the beam across a small aperture. To reach the target, electrons must pass through the hole in an axially symmetric arrangement of strong permanent magnets required to operate the magnetic bottle. From the recorded multi-hit sequence of electron arrival times on the microchannel plate detector, a kinetic energy spectrum is built that allows an analysis of the elastic and inelastic electron scattering channels by means of the coincidence technique. After a description of the instrumental configuration and discussion of suitable working parameters, the results of an angle-integrated (e, 2e) experiment are presented for 800 eV electron scattering on argon atoms.

We present a theoretical approach for describing collective x-ray emission processes in extended multilevel targets, based on a combination of propagation equations for the quantum correlation functions and the semiclassical Maxwell-Bloch equations. Such a description overcomes the key deficiencies of the two constituent sets of equations, which have until now been independently used to describe these phenomena. The model developed is employed to study the spectral properties of superfluorescence of $K\ensuremath{\alpha}$ emission in zinc at $\ensuremath{\sim}8630\phantom{\rule{4pt}{0ex}}\mathrm{eV}$ after inner-shell photoionization with intense attosecond free-electron laser pulses. At high pump intensities, the numerical simulations predict a splitting of the $K{\ensuremath{\alpha}}_{1}$ emission line due to a self-induced Autler-Townes effect, which could readily be observed with standard high-resolution x-ray spectrometers. As short duration of the pump pulse is one of the crucial parameters for the manifestation of this phenomenon in the hard-x-ray regime, experimental verification could be possible due to the most recent developments of free-electron laser sources.

For an atomic state with two electrons missing from different core orbitals one may assume that the deeper hole decays first. However, it is quite probable that the double core-hole state will decay by emission of a slow Auger electron where the deeper core hole remains a spectator, especially if the outer core hole can be filled by Coster-Kronig transition, while the deeper cannot. We study here the competition of both Auger decay channels in a model system, the $1s2s2{p}^{6}(3s/3p)$ states of $\mathrm{N}{\mathrm{e}}^{+}$ ions. As the phenomenon can take place in any decay chain involving multiple core-excited states it can be critical to understand the ion yields, the electron and x-ray emission spectra, and the molecular fragmentation.

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.

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.

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.

International audience; The detailed study of single photon multiple ionization processes requires the detection in coincidence of all the electrons emitted from the same ionization event. The advent of magnetic bottle experiments made possible the development of this multi-electron coincidence spectroscopy. First we will briefly review the achievements of this technique. Then we will illustrate more specifically its high sensitivity taking as an example the decay by emission of three Auger electrons of 2p and 2s holes in argon. Our results show that the processes are completely different depending on the initial core hole: the three Auger electrons are emitted dominantly in a simultaneous path for the 2p case, but in cascade for the 2s one.

Imaging Mass Spectroscopy (IMS) is a unique research tool providing localization and identification of a wide range of biomolecules as essential data to understand biochemical processes in living organisms. Secondary Ion Mass Spectrometry with high-energy heavy ions (MeV-SIMS) is emerging as a promising IMS technique for chemical imaging of biological tissue.We measured the molecular mass spatial distributions in leaves of khat (Catha edulis). Khat is a natural drug plant, native to eastern Africa and the Arabian Peninsula. In these countries, fresh leaves are being chewed by significant part of population. It was reported that 80% of the adult population in Yemen chew the khat leaves. The main stimulating effects of khat are induced by a monoamine alkaloid called cathinone. During leaf ageing, cathinone is further metabolised to cathine and norephedrine. Earlier studies identified the alkaloids in khat, however little is known on their spatial distribution, reflecting the biosynthesis and accumulation in the tissue.Chemical mapping of alkaloids on cross-sections of khat leaves by MeV-SIMS was done at JSI by a pulsed 5.8 MeV Cl-35(6+) beam, focused to a diameter of 15 mu m, using a linear time-of-flight (TOF) spectrometer with a mass resolution of 500. In addition, measurements of MeV-SIMS mass spectra were performed at Kyoto University by a continuous broad beam of 6 MeV Cu-63(4+) ions at an orthogonal TOF spectrometer with a high mass resolution of 11,000. Sections of leaves were analysed and mass spectra obtained at both MeV-SIMS setups were compared. Tissue-level distributions of detected alkaloids are presented and discussed. (C) 2017 Elsevier B.V. All rights reserved.

We calculate the spectra of electrons emitted upon Auger decay of the $2p$ vacancy in chlorine. The vacant atomic and ionic states are populated by a single-photon absorption from the ground state of the chlorine atom and are tested by comparing the calculated photoabsorption spectrum with the existing theoretical and experimental photoionization data. The agreement is reasonably good, although the calculated Auger decay rates and oscillator strengths of the low-lying states are overestimated due to neglect of the core polarization effects. In the absence of any published experimental result, the nonresonant $L\ensuremath{-}{M}_{23}^{2}$ Auger spectrum of Cl at 220 eV photon energy is compared with the Cl $L\ensuremath{-}{V}^{2}$ Auger spectrum of HCl, measured at 235 eV photon energy. The calculated spectator and participator resonant Auger spectra of some strongly photoexcited Cl $2{p}^{\ensuremath{-}1}$ states are presented for future reference.

We present a method for measuring a complete frequency map of laser-dressed states with femtosecond lifetimes. It is based on collecting decay products as a function of the frequency of the excitation pulse and its delay with respect to the linearly chirped laser pulse, centered at the resonant transition frequency. The method has been tested on the case of laser-coupled 2s2p (1) P-0 and 2p(2) S-1(e) autoionizing resonances in He and is applicable to other quantum systems with short-lived states. When the laser coupling effects are known, the excitation pulse properties can be extracted from the map.

We present a theoretical study of self-amplification of extreme ultraviolet light in a helium gas target. Resonant excitation to the $3a\phantom{\rule{0.16em}{0ex}}^{1}P^{o}$ doubly excited state below the $N=2$ threshold by $100\phantom{\rule{0.28em}{0ex}}\mathrm{fs}$ free-electron laser pulses is followed by fluorescence at $40.7\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ photon energy. The process is modeled by a three-level atomic system coupled to the continuum and described by the Maxwell-Bloch equations. The evolution of state populations and radiation fields is studied over a wide range of pump intensities and target pressures, clearly showing the regions of spontaneous emission, amplification, and saturation of light emitted in the forward direction. The treatment includes both coherent and SASE pump pulses. In both cases the amplified pulses are temporally coherent and exhibit a duration similar to that of the pump pulses.

Single-site Double-Core Hole (ss-DCH or K−2) and two-site Double-Core Hole (ts-DCH or K−1K−1) photoelectron spectra including satellite lines were experimentally recorded for the aromatic C6H6 molecule using the synchrotron radiation and multielectron coincidence technique. Density functional theory and post-Hartree-Fock simulations providing binding energies and relative intensities allow us to clearly assign the main K−2 line and its satellites. K−1K−1 states’ positions and assignments are further identified using a core-equivalent model. We predict that, contrary to what has been observed in the C2H2n series of molecules, the K−1K−1 energy-level ordering in C6H6 does not reflect the core-hole distances between the two holes.Single-site Double-Core Hole (ss-DCH or K−2) and two-site Double-Core Hole (ts-DCH or K−1K−1) photoelectron spectra including satellite lines were experimentally recorded for the aromatic C6H6 molecule using the synchrotron radiation and multielectron coincidence technique. Density functional theory and post-Hartree-Fock simulations providing binding energies and relative intensities allow us to clearly assign the main K−2 line and its satellites. K−1K−1 states’ positions and assignments are further identified using a core-equivalent model. We predict that, contrary to what has been observed in the C2H2n series of molecules, the K−1K−1 energy-level ordering in C6H6 does not reflect the core-hole distances between the two holes.

To broaden our analytical capabilities with molecular imaging in addition to the existing elemental imaging with micro-PIXE, a linear Time-Of-Flight mass spectrometer for MeV Secondary Ion Mass Spectrometry (MeV-SIMS) was constructed and added to the existing nuclear microprobe at the Jožef Stefan Institute. We measured absolute molecular yields and damage cross-section of reference materials, without significant alteration of the fragile biological samples during the duration of measurements in the mapping mode. We explored the analytical capability of the MeV-SIMS technique for chemical mapping of the plant tissue of medicinal cannabis leaves. A series of hand-cut plant tissue slices were prepared by standard shock-freezing and freeze-drying protocol and deposited on the Si wafer. We show the measured MeV-SIMS spectra showing a series of peaks in the mass area of cannabinoids, as well as their corresponding maps. The indicated molecular distributions at masses of 345.5 u and 359.4 u may be attributed to the protonated THCA and THCA-C4 acids, and show enhancement in the areas with opened trichome morphology.

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.

Single photon simultaneous core ionization/core excitation (K−2V) of the Benzene molecule has been observed experimentally, using synchrotron radiation, by electron coincidence spectroscopy with a magnetic bottle time-of-flight electron spectrometer and reveals a rich spectrum. DFT and Post–Hartree–Fock calculations provide detailed assignments of K−2V states. The specific Auger decay of these states has also been determined experimentally with a new technique to improve the energy resolution.

In this work, we characterise the performance of a Sharp optical aerosol sensor model GP2Y1010AU0F. The sensor was exposed to different environments: to a clean room, to a controlled atmosphere with known aerosol size distribution and to the ambient atmosphere on a busy city street. During the exposure, the output waveforms of the sensor pulses were digitised, saved and a following offline analysis enabled us to study the behaviour of the sensor pulse-by-pulse. A linear response of the sensor on number concentration of the monosized dispersed PSL particles was shown together with an almost linear dependence on particle diameters in the 0.4 to 4 micrometer range. The gathered data about the sensor were used to predict its response to an ambient atmosphere, which was observed simultaneously with a calibrated optical particle counter.

Synopsis We have observed the autoionization of the laser-coupled 2s2p 1 Po and 2p 2 1 Se resonances in helium. The ions were collected while varying the frequency and delay of the extreme-ultraviolet (EUV) excitation pulse with respect to the linearly chirped visible (VIS) laser pulse. From the measured frequency-delay map the Autler-Townes splitting, the EUV-VIS cross-correlation and the linear chirp parameter were extracted.

We present a theoretical study of He $2\phantom{\rule{0.16em}{0ex}}^{1}P--2\phantom{\rule{0.16em}{0ex}}^{1}S$ emission from a helium gas, where the upper atomic state is prepared by a 100 fs laser pulse resonant with the $1\phantom{\rule{0.16em}{0ex}}^{1}S--2\phantom{\rule{0.16em}{0ex}}^{1}P$ transition. The fluorescence signal emitted in the forward direction at 2059 nm and the transmitted signal at $58.4\phantom{\rule{0.28em}{0ex}}\mathrm{nm}$ are followed in time starting with the low pump intensity regime where the single-atom spontaneous emission results in a characteristic exponential decay. By increasing the gas density and pump intensity, collective effects such as self-amplified spontaneous emission and superfluorescence modify the temporal dependence of the radiation field by amplifying the radiation pattern as well as changing its delay and intensity distribution. The extended Maxwell-Bloch simulation of the corresponding three-level $\mathrm{\ensuremath{\Lambda}}$ system in one spatial dimension covers emission delays of up to 2.4 ns, reaching beyond the natural lifetime of the $2\phantom{\rule{0.16em}{0ex}}^{1}P$ state.

According to the Beer-Lambert law, the spectral density of weak electromagnetic radiation is attenuated exponentially, with the characteristic length depending on atomic density and the frequency-dependent photoabsorption cross section of the target. We discuss an analog of the Beer-Lambert law in the time domain, showing that the temporal profile of the initial light pulse enters explicitly into each term of expansion of the exponential function as a multiconvolution with the corresponding temporal response of an atom. The form invokes a description of pulse propagation in terms of the temporal base functions, which may be precalculated for a chosen initial pulse shape, allowing us to obtain the attenuated profile at a given target depth simply by summing up a sufficient number of weighted base functions. The variant with a 100-fs initial Gaussian pulse is worked out in detail, with the atomic response exhibiting either pure exponential or mixed prompt-exponential decay, characteristic of a photoexcited bound state or a Fano resonance. The method is shown to be valid for an arbitrary temporal profile of the initial electric field and is illustrated for pulses resonantly tuned to the low-lying doubly excited states of the He atom.

We report results of analysis of a month-long measurement of indoor air and environment quality parameters in one gym during sporting activities such as football, basketball, volleyball, badminton, boxing, and fitness. We have determined an average single person's contribution to the increase of temperature, humidity, and dust concentration in the gym air volume of 12500 m(3) : during 90-min exercise performed at an average heart rate of 143 ± 10 bpm, a single person evaporated 0.94 kg of water into the air by sweating, contributed 0.03 K to the air temperature rise and added 1.5 μg/m(3) and 5 ng/m(3) to the indoor concentration of inhalable particles (PM10 ) and Ca concentration, respectively. As the breathing at the observed exercise intensity was about three times faster with respect to the resting condition and as the exercise-induced PM10 concentration was about two times larger than outdoors, a sportsman in the gym would receive about a sixfold higher dose of PM10 inside than he/she would have received at rest outside.

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.

We present the main characteristics of the experimental set-up used to perform gas-phase RIXS studies in the tender X-ray range. A complete in-vacuum curved-crystal X-ray emission spectrometer in Johansson geometry has been built for a 2–6 keV energy range with sub natural line-width energy resolution. The spectrometer operates in a dispersive geometry, employing a relatively large X-ray source placed inside the Rowland circle and a position sensitive detection of diffracted X-rays. A short review of the most recent experimental applications is given focusing on RIXS studies on isolated atoms and molecules.

Photoinduced reformation of chemical bonds is investigated in the CH3Cl molecule experimentally and computationally. The observation of stable HCl+ fragment formation after resonant Cl 2p photoexci ...

We present a theoretical and experimental study of resonant inelastic x-ray scattering on a large group of chlorinated hydrocarbons: CH3Cl, CH2Cl2, CHCl3, CCl4, CH3CH2Cl, ClCH2CH2Cl, CH3CHCl2, CH3CCl3, C2H2Cl2-iso, C2H2Cl2-cis, C2H2Cl2-trans, and C6H5Cl. Differences in structural and dynamical properties of the molecules generated by diverse chemical environments are observed in the measured Cl(K(α)) spectral maps as well as in the Cl(K) total fluorescence yield spectra. The energy position, relative intensity, and the width of the Franck-Condon distribution of low-lying σ* and π* resonances are extracted by a fitting procedure taking into account the experimental broadening. The theoretical values obtained with the transition potential and Δ Kohn-Sham methods are in good agreement with the experimental parameters indicating subtle differences due to variations in the molecular structure.

We have observed ${L}_{23}^{2}\ensuremath{-}{M}^{3}$ Auger decay in argon where a double vacancy is filled by two valence electrons and a single electron is ejected from the atom. A well-resolved spectrum of these two-to-one electron transitions is compared to the result of the second-order perturbation theory and its decay branching ratio is determined.

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.

In this work, a Johansson-type crystal spectrometer was employed to record the high-resolution L X-ray emission spectra of pure Ag, Pd and Cd target in order to determine minimum detection limits (MDL) for trace amounts of Pd and Cd in silver. The X-ray emission was induced by a 3 MeV proton beam as well as by monochromatic synchrotron radiation with excitation energy tuned just below the Ag L3 edge. As a direct consequence of extremely high spectrometer resolution reaching below the natural line widths of the measured L X-ray lines, detection limits of a few tens of parts per million were reached in case of proton excitation. These limits were additionally lowered by an order of magnitude using energy-selective photoexcitation with synchrotron radiation as the signal from the resonant Raman scattering (RRS) was completely separated from the Pd signal. The method presented in this work can be used in general to substantially improve detection limits in case of trace elements with atomic number in the close vicinity of the atomic number of the target matrix element. Copyright © 2011 John Wiley & Sons, Ltd.

We have measured the elemental concentrations in aerosols with a 2-h time resolution in two different types of working environment: a chemistry laboratory dealing with the processing of advanced nanoparticulate materials and a medium-sized machine workshop. Non-stop 10-day and 12-day samplings were performed at each location in order to determine the concentration trends during the non-working/working and weekday/weekend periods. Supplementary measurements of PM10 aerosols with a 2-day sample collection time were performed with a standard Gent PM10 sampler to compare the elemental concentrations with the time-averaged concentrations detected by the 2D step-sampler. The concentrations were determined a posteriori by analyzing the x-ray spectra of aerosol samples emitted after 3-MeV proton bombardment. The PM10 samples collected in the chemistry laboratory were additionally inspected by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) to determine the chemical compositions of the individual particles. In the workshop, a total PM10 mass sampling was performed simultaneously with a minute resolution to compare the signal with typical outdoor PM10 concentration levels. A factor analysis of the time-resolved dataset points to six and eight factors in the chemistry laboratory and the machine workshop, respectively. These factors describe most of the data variance, and their composition in terms of different elements can be related to specific indoor activities and conditions. We were able to demonstrate that the elemental concentration sampling with hourly resolution is an excellent tool for studying the indoor air pollution. While sampling the total PM10 mass concentration with a minute resolution may lack the potential to identify the emission sources in a “noisy” environment, the time averaging on a day time scale is too coarse to cope with the working dynamics, even if elemental sensitivity is an option.

Photon-induced fragmentation of a full set of chlorinated methanes (CH3Cl, CH2Cl2, CHCl3, CCl4) has been investigated both experimentally and computationally. Using synchrotron radiation and electron-ion coincidence measurements, the dissociation processes were studied after chlorine 2p electron excitation. Experimental evidence for CH3Cl and CH2Cl2 contains unique features suggesting that fast dissociation processes take place. By contrast, CHCl3 and CCl4 molecules do not contain the same features, hinting that they experience alternative mechanisms for dissociation and charge migration. Computational work indicates differing rates of charge movement after the core-excitation, which can be used to explain the differences observed experimentally.

We recorded a series of spectral maps of a hematite particle by combining a scanning proton microbeam excitation with detection of X-rays by a Si(Li) spectrometer equipped with polycapillary lens. The particle was driven through the sensitive microvolume to allow for a reconstruction of concentration in three dimensions. Beside the description of the experiment, important aspects of data analysis are emphasized to show the potential of the confocal micro-PIXE (Proton Induced X-ray Emission) imaging method: at present, this is limited by the focusing properties of the polycapillary lens.

A detailed report about the confocal experiment and the corresponding data analysis is presented to determine local atomic concentrations in a thick sample with a micrometer resolution. X-ray emission from a quartz substrate, loaded by aerosol particles, was induced by a scanning proton microbeam and observed by an Si(Li) spectrometer whose field of view was narrowed by a polycapillary lens. A series of X-ray images were recorded at different positions of the sample along the microbeam axis when the particles were driven through the sensitive microvolume. The concentrations reconstructed in three dimensions were used to extract penetration profiles of the strongest X-ray emitters (Fe, Ca, S) in an aerosol sample together with the surface profile of the matrix (Si). The results show exponentially dumped depth profiles with characteristic length depending on particle size. Copyright © 2009 John Wiley & Sons, Ltd.

In digital nuclear calorimetry, the effect on measured pulse amplitudes by piling up of pulses can be compensated based on the pulses' respective timestamps, making use of the fact that, for stable pulse shapes, the amount of pile-up induced error at each pulse amplitude measurement is completely determined by the amplitudes and precise occurrences in time of the neighboring pulses. We propose here a compensation method, based on the above observation, suitable for real-time as well as off-line implementation. Successful tests performed off-line both on synthetic and experimental data are shown as a proof of principle. We further propose a draft architectural approach to real-time compensation schemes of this functionality and the corresponding interaction with the experimental controls. (C) 2009 Elsevier B.V. All rights reserved.

We discuss general characteristics of the resonant X-ray scattering and briefly illustrate its applications in atomic, molecular and solid state physics by a few selected examples. The Ljubljana high resolution spectrometer set-up is presented, which was recently employed at ELETTRA and ESRF synchrotron beamlines to study X-ray emission of inner-shell excited states of xenon and argon, and of simple sulfur containing molecules and solid compounds.

We summarize recent results dealing with high resolution (resonant) X-ray spectroscopy of atomic and molecular targets in the tender X-ray energy region. We comment on advantages, new possibilities and problems related to RIXS spectroscopy with respect to the standard photoabsorption technique, where scanning the probe energy is the only option. In particular, three research areas are covered: X-ray emission mediated by energy dependent photoabsorption to multi-electron excited states, the Cl K core-hole clock studies exemplified by systematic study of chloro(fluoro)-hydrocarbon targets and the polarization dependent X-ray emission studies. Due to its spectral selectivity and simultaneous detection capability, high resolution wavelength dispersive X-ray spectroscopy has the capability to resolve structural and dynamical properties of matter within new instrumentation frontiers.

International audience; We present an experimental and theoretical study of resonant inelastic x-ray scattering (RIXS) in the carbon disulphide CS 2 molecule near the sulfur K-absorption edge. We observe a strong evolution of the RIXS spectral profile with the excitation energy tuned below the lowest unoccupied molecular orbital (LUMO) absorption resonance. The reason for this is twofold. Reducing the photon energy in the vicinity of the LUMO absorption resonance leads to a relative suppression of the LUMO contribution with respect to the emission signal from the higher unoccupied molecular orbitals, which results in the modulation of the total RIXS profile. At even larger negative photon-energy detuning from the resonance, the excitation-energy dependence of the RIXS profile is dominated by the onset of electron dynamics triggered by a coherent excitation of multiple electronic states. Furthermore, our study demonstrates that in the hard x-ray regime, localization of the S 1s core hole occurs in CS 2 during the RIXS process because of the orientational dephasing of interference between the waves scattering on the two sulfur atoms. Core-hole localization leads to violation of the symmetry selection rules for the electron transitions observed in the spectra.

International audience; The simultaneous core ionization and core excitation process (or K-2V process) induced by absorption of a single photon provides the basis of a new spectroscopy that offers both advantages of X-ray Photoelectron Spectroscopy (XPS) and near-edge x-ray absorption fine structures (NEXAFS) spectroscopy

We present in detail a theoretical model that provides absolute cross sections for simultaneous core-ionization core-excitation (K(-2)V) and compare its predictions with experimental results obtained on the water molecule after photoionization by synchrotron radiation. Two resonances of different symmetries are assigned in the main K(-2)V peak and comparable contributions from monopolar (direct shake-up) and dipolar (conjugate shake-up) core-valence excitations are identified. The main peak is observed with a much greater width than the total experimental resolution. This broadening is the signature of nuclear dynamics.

The formalism developed in the companion Paper I is used here for the interpretation of spectra obtained recently on the nitrogen molecule. Double core-hole ionization K(-2) and core ionization-core excitation K(-2)V processes have been observed by coincidence electron spectroscopy after ionization by synchrotron radiation at different photon energies. Theoretical and experimental cross sections reported on an absolute scale are in satisfactory agreement. The evolution with photon energy of the relative contribution of shake-up and conjugate shake-up processes is discussed. The first main resonance in the K(-2)V spectrum is assigned to a K(-2)π(∗) state mainly populated by the 1s→ lowest unoccupied molecular orbital dipolar excitation, as it is in the K(-1)V NEXAFS (Near-Edge X-ray Absorption Fine Structure) signals. Closer to the K(-2) threshold Rydberg resonances have been also identified, and among them a K(-2)σ(∗) resonance characterized by a large amount of 2s/2p hybridization, and double K(-2)(2σ(∗)/1π/3σ)(-1)1π(∗2) shake-up states. These resonances correspond in NEXAFS spectra to, respectively, the well-known σ(∗) shape resonance and double excitation K(-1)(2σ(∗)/1π/3σ)(-1)1π(∗2) resonances, all being positioned above the threshold.

International audience; In the last five years, a strong experimental and theoretical activity has been dedicated to the study of inner-shell double photoionization. Almost simultaneously, between 2009 and 2011, different experiments were performed using two different light sources: well established third generation synchrotron light sources that exist for more than two decades and recently developed x-ray free electron lasers (X-FEL) that provide brightness about 10 orders of magnitude higher. The high photon flux of X-FEL has made possible the successive absorption of many x-ray photons by inner-shell electrons in femtosecond timescale. The possibility to create multiple inner-shell vacancies with this new X-FEL light source has resuscitated “prophetic” 25 years old calculations by Cederbaum et al. [1][2] concerning double K-shell ionization that could be of great interest when conventional Electron Spectroscopy for Chemical Analysis (ESCA) finds some limitations. As a feedback, this has stimulated new theoretical developments. On the other hand, it was considered practically out of reach to observe such states with conventional third generation synchrotron light sources due to the very weak probability to eject two inner-shell electrons by a single photon when the dominant process, that could mask everything else, is single inner-shell ionization. However, due to the development of very efficient detection techniques, it was also possible to perform spectroscopy of double core-hole states with excellent accuracy using third generation synchrotron sources.In this paper we give an outlook, on the basis of recently published results, of the complementary of these light sources for double core-hole spectroscopy. Some new developments and results are also presented with a prospective of what could be done in the future with the technical breakthrough that will be necessary to improve further our understanding of chemical analysis.