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The effect of the deposition of kinetic energy and neutralization energy of slow highly charged xenon ions on the process of the nanostructures creation at the surface of gold nanolayers is investigated. The nanolayers of thickness of 100 nm were prepared by e-beam evaporation of gold on crystalline silicon Si(100) substrate. The samples were irradiated at the Kielce EBIS facility of the Jan Kochanowski University (Kielce, Poland), under high vacuum conditions. The irradiations were performed for constant kinetic energy 280 keV and different ions charge states (Xe$^{q+}$, q = 25, 30, 35, 36 and 40) and for constant charge state Xe$^{35+}$ and different kinetic energies: 280 keV, 360 keV, 420 keV and 480 keV. The fluence of the ions was on the level of 10$^{10}$ ions/cm$^2$. Before and after irradiation the nanolayer surfaces were investigated using the atomic force microscope. As the result, well pronounced modifications of the nanolayer surfaces in the form of craters have been observed. A systematic analysis of the crater sizes (diameter on the surface and depth) allowed us to determine the influence of the deposited kinetic and the neutralization energy on the size of the obtained nanostructures. The results are theoretically interpreted within the micro-staircase model based on the quantum two-state vector model of the ionic Rydberg states population. The charge dependent ion-atom interaction potential inside the solid is used for the calculation of the nuclear stopping power. According to the model the formation of the nanostructures is governed by the processes of the ionic neutralization in front of the surface and the kinetic energy loss inside the solid., Comment: 12 pages, 7 figures, Submitted to Vacuum journal on May 29th, 2022

The main advantage of wavelength-dispersive spectrometers applied in X-ray study is their high energy resolution. The design and construction of spectrometer, usually dedicated to the specific experimental systems, for example synchrotron based setups, need information about the characteristics of the main elements of the spectrometer such as X-ray optics elements, crystals and detectors. Such information can be obtained using Monte-Carlo simulations. In this paper, the Monte-Carlo simulations of X-ray tracing in parallel-beam wavelength-dispersive spectrometer (PBWDS), equipped with polycapillary optics, are presented and discussed. The study concentrates on the description of the polycapillary model, simulations of the properties of X-ray polycapillary optics and, finally, on the simulations of X-ray track in the spectrometer designed and installed at the ID21 beamline at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). The results of simulations were compared with experimental data obtained for different registered X-ray energies and spectrometer crystals, showing good agreement. The obtained results showed that the X-ray transmission in the tested polycapillary optics is at the level of 15%, while the divergence of the outgoing beam changes from 8 mrad to 3 mrad with an increase of photon energy from 2 keV to 10 keV. The spectrometer provides an energy resolution of 5 eV and 33 eV in the energy range of 1.4 keV - 6.5 keV. The developed simulation program can be successfully used for the construction of spectrometers dedicated to the different experimental conditions. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

X-ray diffraction (XRD), grazing incidence X-ray diffraction (GIXRD) and X-ray reflectometry (XRR) techniques were applied for analysis of titanium (Ti) and titanium (IV) oxide (TiO2) nanolayers with thickness of 25 nm, 50 nm and 75 nm deposited on silicon, quartz and BK7 glass substrates. The aim of studies was investigating the crystal structure and morphology of the nanolayers in dependence on the substrate type. The chemical phases of nanolayers and substrates were determined by using the XRD and GIXRD measurements. The benefits of applying low angle GIXRD and XRR analytical techniques, both for substrate and nanofilm analysis, is discussed based on theoretical calculations and simulations. Additional, analytical capabilities of the XRR technique to nanolayer and substrate morphology analysis are presented. Simulated XRR curves for titanium (Ti) and titanium (IV) oxide nanolayers are discussed depending on the substrate type as well as the substrate and nanolayer roughnesses. Experimental reflectometry curves are presented for all titanium and titanium (IV) oxide nanolayers deposited on the different substrates. As the result of the XRR analysis, the nanolayer thickness and roughness together with substrate roughness are estimated. The mean values of the Ti and TiO2 layer thickness and roughness are presented for all studied samples. The largest roughness, both for nanolayers and for substrates, is obtained for BK7 glass material. In the manuscript, sample properties, experimental setups and measurement conditions are presented in details.

In this work synchrotron radiation based X-ray reflectometry method was applied for determination of morphology of TiO2 nanolayers, unmodified, and irradiated with low energy highly charged Xeq+ ions. Using the synchrotron radiation based X-ray reflectometry technique density, thickness, and roughness of the TiO2 nanolayers were determined. The results showed that the thicknesses of the nanolayers obtained with synchrotron radiation based X-ray reflectometry method agree within the experimental uncertainty with the declared thicknesses. Moreover, the density of the nanolayers is much lower than density of the bulk TiO2 due to their nanometer thickness. The results obtained for irradiated samples suggest possible amorphization and smoothening of the TiO2 nanolayers surface due to interactions of the highly charged ions.

31st International Conference on Photonic, Electronic and Atomic Collisions, ICPEAC XXXI, Deauville, France, 23 Jul 2019 - 30 Jul 2019; Journal of physics / Conference series Conference series [...] 1412, 132031 (2020). doi:10.1088/1742-6596/1412/13/132031, Published by IOP, Bristol

Total reflection X-ray photoelectron spectroscopy (TRXPS) is applied in the analysis of Ti and TiO2 nanolayers deposited on silicon and silicon dioxide substrates. The idea of application of total-reflection phenomenon for exciting X-ray used in the XPS technique is briefly discussed. The experimental setup and measurement conditions for the studied Ti and TiO2 layers are presented. The XPS spectra were registered both for the non-total and total reflection regimes. The survey spectra and C1s, N1s, Ti2p and O1s photoelectron peaks are shown. For energy calibration, the position of C1s photoelectron peak was applied (C-C component, binding energy 284.8 eV). The peak to background ratios are discussed as regards the dependence of the excitation angle. An increase of this ratio for the glancing angle 1°, being below critical angle of the X-ray beam and sample material, results in an improvement of XPS detection limit by factor up to 2. In the case of the Ti nanolayer, additionally, the thickness of the overlayer TiO2 is determined. As an example of applying the TRXPS technique, the analysis of Ti nanolayers implanted by highly charged Xe35+ ions of 280 keV energy is discussed. The Xe3d and O1s photoelectron peaks are presented and discussed.

The measured M-X-ray production cross sections for protons, which are used in the particle induced X-ray emission (PIXE) technique, are systematically underestimated for low impact energies by the ECPSSR and ECUSAR theories. These theories, which are based on the plane wave Born approximation (PWBA) and use the screened hydrogenic wave functions, include corrections for the projectile Coulomb deflection and electron relativistic and binding effects. In the present paper, in order to interpret the observed disagreement at low impact energies, the systematic calculations of the M-shell ionization cross sections for gold were performed using the semiclassical (SCA) and the binary encounter (BEA) approximations in order to identify a role of the electronic wave function and electron binding effects. In these calculations the different wave functions, from nonrelativistic hydrogenic to selfconsistent Dirac-Hartree-Fock, were considered and the binding effect was treated within extreme separated- (SA) and united-atoms (UA) limits. The results are discussed in details and the observed discrepancies are attributed to inadequate description of the electron binding effect at the lowest impact energies for which the molecular approach is required.

The measurements of the M- and N-shell ionization probabilities in gold bombarded by highly charged S q+ (q = 4–14) ions of energy 0.4–3.8 MeV/amu are reported. The ionization probabilities were extracted from the measured L-X-ray spectra which were substantially modified by the multiple ionization effects. The observed L-X-ray line shifts and broadening allowed us (Banaś et al., 2002) to extract both the M- and N-shell ionization probabilities for the zero impact parameter. These ionization probabilities, which correspond to the moment of X-ray emission , were correlated with the ionization probabilities for the moment of ion impact ionization by using the vacancy rearrangement procedure developed here. In this way the ionization probabilities for the moment of ion impact multiple ionization were obtained. By comparing to the theoretical predictions of the semiclassical approximation (SCA) (Trautmann and Kauer, 1989) and the “geometrical model” (GM) (Sulik et al., 1987) based on the binary encounter approximation (BEA), the role of the electronic wave functions and the binding effect is discussed. Generally, the calculations using the hydrogenic wave functions reproduce the measured ionization probabilities.

Total reflection X-ray fluorescence analysis and X-ray powder diffraction were used for elemental and chemical composition analysis of 83 samples of human kidney stones. Samples came from patients after surgical removal of stones. Elements such as P, K, Ca, Fe, Zn, Ni, Br, Sr, and Pb were determined in all samples. Other elements Mg, S, Cl, Ti, V, Cr, Mn, Cu, Se, Rb, I, and Bi were found in some of the analyzed kidney stones (censoring effect). Descriptive statistics were calculated for all elements paying particular attention to the censored elements. From diffraction measurements, the following crystalline substances were determined in the stones: apatite, struvite, uric acid, weddellite, whewellite, magnesium phosphate, and calcium phosphate. Information of chemical composition was applied to classify the analyzed kidney stone into four groups. Statistical analysis of the results included multigroups comparison, testing of element concentration distribution, and elemental correlations in the dependence of kind of kidney stones. The presented studies are part of wider microbiological studies focusing on the correlation between different kinds of bacteria and fungi presented in the samples of kidney stones and their elemental as well as chemical composition. Information on stone composition can be helpful in understanding kidney stone formation and complemented by additional metabolic blood and urine tests. This, in turn, can lead to appropriate medical treatment together with the reduction of the risk as regards forming new stones.

Deficiency or excess of elements could disrupt proper functioning of the human body and could lead to several disorders. Determination of their concentrations in different biological human fluids and tissues should become a routine practice in medical treatment. Therefore the knowledge about appropriate element concentrations in human organism is required. The purpose of this study was to determine the concentration of several elements (P, S, Cl, K, Ca, Cr, Fe, Cu, Zn, Se, Br, Rb, Pb) in human serum and to define the reference values of element concentration. Samples of serum were obtained from 105 normal presumably healthy volunteers (66 women aged between 15 and 78 years old; 39 men aged between 15 and 77 years old). Analysis has been done for the whole studied population and for subgroups by sex and age. It is probably first so a wide study of elemental composition of serum performed in the case of Świetokrzyskie region. Total reflection X-ray fluorescence (TXRF) method was used to perform the elemental analysis. Spectrometer S2 Picofox (Bruker AXS Microanalysis GmbH) was used to identify and measure elemental composition of serum samples. Finally, 1st and 3rd quartiles were accepted as minimum and maximum values of concentration reference range.

A particular subject of X-ray fluorescence analysis is its application in studies of the multielemental sample of composition in a wide range of concentrations, samples with different matrices, also inhomogeneous ones and those characterized with different grain size. Typical examples of these kinds of samples are soil or geological samples for which XRF elemental analysis may be difficult due to XRF disturbing effects. In this paper the WDXRF technique was applied in elemental analysis concerning different soil and geological samples (therapeutic mud, floral soil, brown soil, sandy soil, calcium aluminum cement). The sample morphology was analyzed using X-ray microtomography technique. The paper discusses the differences between the composition of samples, the influence of procedures with respect to the preparation of samples as regards their morphology and, finally, a quantitative analysis. The results of the studies were statistically tested (one-way ANOVA and correlation coefficients). For lead concentration determination in samples of sandy soil and cement-like matrix, the WDXRF spectrometer calibration was performed. The elemental analysis of the samples was complemented with knowledge of chemical composition obtained by X-ray powder diffraction.

Particle-induced X-ray emission (PIXE) technique is usually applied using typically 1 MeV to 3 MeV protons or helium ions, for which the ion-atom interaction is dominated by the single ionization process. For heavier ions the multiple ionization plays an increasingly important role and this process can influence substantially both the X-ray spectra and atomic decay rates. Additionally, the subshell coupling effects are important for the L- and M-shells ionized by heavy ions. Here we discuss the main features of the X-ray emission induced by heavy ions which are important for PIXE applications, namely, the effects of X-ray line shifts and broadening, vacancy rearrangement and change of the fluorescence and Coster–Kronig yields in multiple ionized atoms. These effects are illustrated here by the results of the measurements of L X-ray emission from heavy atoms bombarded by 6 MeV to 36 MeV Si ions, which were reported earlier. The strong L-subshell coupling effects are observed, in particular L 2 -subshell, which can be accounted for within the coupling subshell model (CSM) developed within the semiclassical approximation. Finally, the prospects to use heavy ions in PIXE analysis are discussed.

The influence of activation temperature on the structure of halloysite mineral (HM) from the “Dunino” strip mine (Poland), activated with 25 wt% sulfuric(VI) acid, was investigated using a surface sensitive X-ray photoelectron spectroscopy (XPS) method. XPS measurements were performed for commercially available halloysite nanoclay (HNT), raw halloysite mineral (HS) directly from the mine and samples of a halloysite mineral (HM) activated at different temperatures up to 100 °C. The XPS spectra were measured in wide range of the electron binding energy (survey spectra) and in the region of O, Al and Si photoelectron peaks (detailed spectra). Changes of photoelectron peak positions and their intensities are discussed as a function of activation temperature. Elemental composition of HS, HM and HNT surfaces was estimated and compared with bulk results obtained using the wavelength dispersive X-ray fluorescence (WDXRF) method. Concentration changes of O, Al, Si and Fe obtained by both XPS and WDXRF measurements are discussed. An increase of the silicon to aluminum ratio (Si/Al), as a result of higher activation temperature, is demonstrated.

Synopsis In this work we have systematically studied process of energy deposition and formation of nanostructures on metallic (Au nanolayer) surfaces as a result of the irradiation with slow highly charged xenon ions (HCI). Well pronounced modifications of the surfaces in form of craters were observed. We found that, in the systems considered, the kinetic energy influences the crater depth, while the potential energy affects the crater size at the surface. This finding showed that for gold nanolayers the potential energy plays important role in the nanostructures creation.

Synopsis Two-Electron One-Photon (TEOP) X-ray transitions were observed for the first time in collisions of highly charged Xe ions with metallic Be surface. The intensities of TEOP X-rays are well described by performed MCDF for one-electron one-photon (OEOP) dipole-allowed transition of Paschen and Brackett series assuming constant TEOP/OEOP branching ratio. The importance of the Internal Dielectronic Excitation (IDE) in relaxation of hollow Xe ions/atoms has been evidenced and discussed.

We report here on the progress in the X-ray spectroscopy program at the EBIS-A facility installed recently at the Institute of Physics of Jan Kochanowski University in Kielce. In this facility the beams of low-energy highly charged ions (HCI) produced by the Dresden EBIS-A ion source, after extraction and charge-state separation in the double focusing magnet, are directed to the experimental UHV chamber equipped with a 5-axis universal sample manipulator. The X-rays emitted in interaction of the highly charged ions with solids can be measured by an energy dispersive X-ray silicon drift detector (SDD) and/or a wavelength-dispersive X-ray spectrometer (WDS) mounted at the experimental chamber. The surface nanostructures formed by an impact of HCI will be studied by the grazing emission X-ray fluorescence (GEXRF) technique and using a multiprobe surface analysis system based on the X-ray photoelectron spectrometer (XPS) coupled to the UHV chamber of the EBIS-A facility. In this paper a brief description of the facility, X-ray instrumentation and the surface analysis system is given and the first results are presented.

The results of the elemental and chemical composition analysis of human medical samples (blood, serum, hair, urine, tooth, kidney stones, gallstones) and environmental samples (slag, cereal, vegetables, our, pork bones, pork meat, sh) are presented. The analysis were performed by application of the total re ection X-ray uorescence, wavelength dispersive X-ray uorescence and X-ray powder di raction methods. With X-ray uorescence methods the following elements were identi ed: O, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Se, Br, Rb, Sr, Zr, I, Ba, and Pb, whose concentrations were from a few ng/g to tens of percent. For some samples the elemental analysis was extended by X-ray powder di raction measurements. With this method the chemical composition was determined. In the paper the experimental setups, methodology of samples preparation and methods of carrying out the measurements are described. As an example the X-ray spectra registered for gallstone sample are discussed in detail. Finally, the results of X-ray di raction and elemental analysis for selected medical and environmental samples are summarized.

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.

Elemental and chemical composition of raw and activated samples of halloysite mineral using wavelength dispersive X-ray fluorescence (WDXRF), total reflection X-ray fluorescence (TXRF) and X-ray powder diffraction (XRPD) methods were determined. As the result, it has been shown that application of the complementary X-ray spectrometry techniques allows very precise observation of changes in composition of halloysite mineral samples caused by its chemical modifications. Sample preparation procedure and usability of the research methods applied are described in details. Procedure of activation of raw halloysite mineral samples by etching them in sulfuric acid of various concentrations has been described and discussed. The ability of the samples to adsorb lead from intentionally contaminated water was tested and confirmed.

X-ray fluorescence analysis methods (wavelength dispersive X-ray fluorescence analysis (WDXRF) and total reflection X-ray fluorescence (TXRF)) and X-ray powder diffraction (XRPD) have been applied in complementary geochemical studies of the Pleistocene till samples. The XRPD technique gave information about the mineral composition of the analyzed samples while the WDXRF and TXRF studies allowed the fast elemental analysis. The till samples were collected from different regions of Holy Cross Mountains (located in central Poland) which are still not unambiguously described in the context of the geochemical studies of the Quaternary sediments. The analysis was concentrated on the geochemical composition of the till samples both for materials occurring on the surface (characterized by continuous weathering processes) and for samples taken from core borehole. The overriding purpose of these studies is determination of the local lithotype of the tills and its lithologic and petrographic diagnostic properties, including the chemical composition of clay and minerals found in the clay. In the presented work the experimental sets up, sample preparation procedure and measurements programme will be discussed in details. Finally, the elemental and mineral compositions will be presented for studied different groups of the samples.

Total reflection X-ray fluorescence (TXRF) and grazing emission X-ray fluorescence (GEXRF) are surface sensitive techniques and can be used for detailed surface studies of different materials, including ultra-low concentration contamination or the lateral and depth distributions of elements. The calibration procedure typically used involves placing a micro-droplet ( ∼ μ l ) of the standard solution onto a silicon wafer (or quartz backing). After evaporation of the solvent, the residual amount of elements is used as a reference standard. Knowledge of the distribution of residue material on the substrate surface is crucial for precise quantification. In the present work the investigation of the lateral distribution of elements in the multielemental calibrating samples, containing the 23 most commonly studied elements, by using the synchrotron radiation based micro X-ray fluorescence is presented. The goal of this project was the study of a uniformity of the elemental distributions and determination of the residual elements morphology depending on the temperature of the drying process. The X-ray images were compared with optical and SEM images. Paper presents in details the experimental setup, sample preparation procedures, measurements and results. In the analysis of the X-ray images of the sample dried in high temperature the censoring approach was applied improving the quality of statistical analysis. The information on the elements distribution in the calibrating samples can be useful for developing more accurate calibration procedures applied in quantitative analysis of surface sensitive TXRF and GEXRF techniques.

The investigations of a compact 6-crystal Johann/Johansson diffraction X-ray spectrometer, covering a wide range (70 eV–15 keV) of photon energies, applied to observe the X-rays emitted from electron bombarded surfaces are discussed in terms of its focusing properties and achievable energy resolution. In the present study the X-ray spectra of Si-K α 1,2 and Al-K α 1,2 X-ray lines excited by 5 keV electron beam were measured using PET and TAP crystal, respectively, in the “out-of-focus” geometry which will be used to study the electron/ion surface interactions at the electron beam ion source (EBIS) facility. The measured X-ray spectra were interpreted in terms of the performed ray-tracing simulations which demonstrate the key features of the “out-of-focus” geometry. It was demonstrated that in this case the energy resolution in the range 1–3 eV for photon energy 1–2 keV can be achieved with an increased acceptance for the extension of X-ray source, of about 1 mm, which is important feature for practical applications. Additionally, a dependence of the X-ray intensity and energy resolution on slit opening was studied in details. The results are important for investigations of surfaces with electron and ion impact, in particular, for the future high-resolution X-ray spectroscopy experiments at the EBIS facility.

Results of the calculations of differential L−shell radiative recombination (RR) rate coefficients for bare uranium ions colliding with free electrons using the nonrelativistic dipole approximation and fully relativistic calculations are reported. The rate coefficients were obtained for very low, in the range of meV, relative electron-ion energies. We demonstrate that even for such low relative ion-electron energies the relativistic effects significantly modify the differential RR rate coefficients for the L−subshells and, as a result, the measurements of the relative electron energy dependence of the L-RR rates could be used for studying of the relativistic effects. These effects are strongest for the L 3-subshell, which is discussed here in more details.

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.

X-ray techniques have evolved over decades to become highly refined tools for a broad range of investigations. Importantly, these approaches rely on X-ray measurements that depend linearly on the number of incident X-ray photons. The advent of X-ray free electron lasers (XFELs) is opening the ability to reach extremely high photon numbers within ultrashort X-ray pulse durations and is leading to a paradigm shift in our ability to explore nonlinear X-ray signals. However, the enormous increase in X-ray peak power is a double-edged sword with new and exciting methods being developed but at the same time well-established techniques proving unreliable. Consequently, accurate knowledge about the threshold for nonlinear X-ray signals is essential. Herein we report an X-ray spectroscopic study that reveals important details on the thresholds for nonlinear X-ray interactions. By varying both the incident X-ray intensity and photon energy, we establish the regimes at which the simplest nonlinear process, two-photon X-ray absorption (TPA), can be observed. From these measurements we can extract the probability of this process as a function of photon energy and confirm both the nature and sub-femtosecond lifetime of the virtual intermediate electronic state., Scientific Reports, 6, ISSN:2045-2322

We have performed femtosecond X-ray spectroscopy measurements after UV photoexcitation of a colloidal solution of ZnO nanoparticles. The results indicate sub-ps hole trapping at oxygen vacancies with shallowly-trapped electrons in the conduction band.

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. Copyright © 2012 John Wiley & Sons, Ltd.

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.

We report the results of the x-ray radiative recombination (RR) experiment at the electron cooler of the ESR storage ring performed, for the first time, for detuned (off-cooling) electron energies. In this experiment the recombination of stored, decelerated bare uranium ions with electrons in the energy range 0–1000 meV was studied by observing K-RR x-ray photons emitted from direct radiative recombination to the lowest n=1 state. In this way the RR process was studied in a state selective manner for several off-cooling electron energies. The measured dependency of the recombination rate on the relative electron energies for K-shell RR x-ray photons are compared with the predictions of both nonrelativistic and fully relativistic calculations for the radiative recombination. A role of the relativistic effects, which contribute substantially for higher relative electron energies, are discussed. Strong enhancement of the recombination rate is observed for the the zero relative electron energy (cooling condition) for the K-shell.

The L-shell X-ray production cross sections have been measured for sulphur ions in the energy range of 12.8–120 MeV for Au and Bi elements. The experimental L X-ray spectra were analyzed using the method that takes into account the multiple ionization in outer shells. The L-subshell ionization cross sections have been obtained from measured X-ray production cross sections for resolved Lα 1,2 Lγ 1 and Lγ 2,3 transitions using the L-shell fluorescence and Coster–Kronig yields modified by the multiple ionization effects in the M and N shells. The results are compared with the predictions of ECUSAR theory, which is the modified ECPSSR approach describing both direct ionization and electron-capture processes and the semiclassical approximation (SCA) calculations for direct ionization. These approaches were modified by the L-subshell coupling effects within the “coupled-subshell model” (CSM). Both modified approaches are in good agreement with the data. Remaining discrepancies are discussed in terms of the L-shell decay rates modified for the multiple ionization effects.

The total reflection X-ray fluorescence method was applied to study the trace element concentrations in human breast malignant and breast benign neoplasm tissues taken from the women who were patients of Holycross Cancer Centre in Kielce (Poland). These investigations were mainly focused on the development of new possibilities of cancer diagnosis and therapy monitoring. This systematic comparative study was based on relatively large (∼ 100) population studied, namely 26 samples of breast malignant and 68 samples of breast benign neoplasm tissues. The concentrations, being in the range from a few ppb to 0.1%, were determined for thirteen elements (from P to Pb). The results were carefully analysed to investigate the concentration distribution of trace elements in the studied samples. The measurements of concentration of trace elements by total reflection X-ray fluorescence were limited, however, by the detection limit of the method. It was observed that for more than 50% of elements determined, the concentrations were not measured in all samples. These incomplete measurements were treated within the statistical concept called left-random censoring and for the estimation of the mean value and median of censored concentration distributions, the Kaplan–Meier estimator was used. For comparison of concentrations in two populations, the log-rank test was applied, which allows to compare the censored total reflection X-ray fluorescence data. Found statistically significant differences are discussed in more details. It is noted that described data analysis procedures should be the standard tool to analyze the censored concentrations of trace elements analysed by X-ray fluorescence methods.

We present a new experiment for the accurate study of the intrashell transition 1s2p 3P2 → 1s2s 3S1 in helium-like uranium near 4.5 keV using a Johann-type Bragg spectrometer with a spherically bent crystal. The focusing property of the bent crystal enhances the spectrometer's efficiency compared to flat crystal spectrometers and it will enable us, for the first time, to evaluate, accurately, the Lamb shift for n = 2 states in highly charged helium-like ions. The data will be acquired at the storage ring ESR of GSI using a fast H-like uranium beam colliding with a gas target. This measurement will provide the most sensitive test for the relativistic electron–electron interaction in a strong Coulomb field.PACS Nos.: 07.85.Nc, 12.20.Fv, 29.30.Kv and 32.30.Rj

The construction and results of the Monte-Carlo ray-tracing simulations for a low energy x-ray crystal spectrometer designed for future experiments at the ESR storage ring with fast highly charged ions are presented. The spectrometer has a radius of the Rowland circle R = 0.5 m and operates in the Johann geometry. The x-rays emitted from a source are diffracted by spherically bent silicon Si(111) crystal and registered by two-dimensional deep depleted back-illuminated CCD camera. The estimated spectrometer efficiency, calculated according to a dynamical theory of x-ray diffraction is about 10−6. The energy resolution of the spectrometer obtained from the simulations is about 0.5 eV. Influence of the source size and Doppler broadening on the spectrometer resolution is discussed.

Depth-profiling measurements by means of synchrotron radiation based grazing XRF techniques, i.e., grazing emission X-ray fluorescence (GEXRF) and grazing incidence X-ray fluorescence (GIXRF), present a promising approach for the non-destructive, sub-nanometer scale precision characterization of ultra shallow ion-implantations. The nanometer resolution is of importance with respect to actual semiconductor applications where the down-scaling of the device dimensions requires the doping of shallower depth ranges. The depth distributions of implanted ions can be deduced from the intensity dependence of the detected X-ray fluorescence (XRF) signal from the dopant atoms on either the grazing emission angle of the emitted X-rays (GEXRF), or the grazing incidence angle of the incident X-rays (GIXRF). The investigated sample depth depends on the grazing angle and can be varied from a few to several hundred nanometers. The GEXRF setup was equipped with a focusing polycapillary half-lens to allow for laterally resolved studies. The dopant depth distribution of the investigated low-energy (energy range from 1 keV up to 8 keV) P, In and Sb ion-implantations in Si or Ge wafers were reconstructed from the GEXRF data by using two different approaches, one with and one without a priori knowledge about the bell-shaped dopant depth distribution function. The results were compared to simulations and the trends predicted by theory were found to be well reproduced. The experimental GEXRF findings were moreover verified for selected samples by GIXRF.

To achieve the low ppb detection level a major experimental effort and optimization of the TXRF setup are required. The new solution described in this paper leads to enhancement of the TXRF intensity and to improved signal/noise ratio. The adjusted quartz reflector allows control of a reflection angle of a photon beam with respect to the crystal surface with high precision up to 0.006°. The installed adjusted diaphragm (followed by the quartz reflector) substantially reduces the level of registered background in the studied range of x-ray energy. The dependence of the x-ray spectra shape, x-ray intensity and detection limit on the diaphragm width and its position on the photon beam as well as on the value of the glancing angle of x-rays from the sample carrier have been studied. The new optimal parameters found result in essential improvement in detection limit equal to ∼1.0 ppb for elements detected in a liquid sample without any special pre-concentration preparation. Also a very good repeatability of measurements has been reached. Copyright © 2006 John Wiley & Sons, Ltd.

Ten samples taken from wooden torches and small fireplaces discovered at the Krzemionki neolithic flint mine localized in central Poland were dated using the AMS facility at Erlangen University. The radiocarbon results points two main periods of exploitation of studied mines, i.e. approximately to 3500–3100 BC and to 3100–2900 BC. The results are discussed in the aspect of the mine chronology. The new radiocarbon dates confirm the previous radiocarbon data obtained from other mine units in this part of the Krzemionki mine complex.

The coupling and binding effects in ionization of L-shell electrons by heavy ions have been studied by measuring the L γ (L–N,O) X-ray transitions in gold excited by an impact of O, Si and S ions in the energy range 0.3–5 MeV/amu. The L-subshell ionization cross sections were extracted from measured X-ray spectra taking into account their substantial modifications due to the multiple ionization effects, which also change the fluorescence and Coster–Kronig yields. In order to interpret the data the L-subshell couplings were incorporated in the theoretical calculations based on the semiclassical approximation (SCA) within the “coupled subshell model” (CSM). Resulting SCA–CSM calculations, which describe the data for oxygen ions quite satisfactory, are further modified to include the saturation of the binding effect in order to describe the data for heavier Si and S ions. We find that the semiclassical SCA–CSM calculations of L-shell ionization by heavy ions ( Z 1 ≫ 1), which include corrections both for coupling and binding saturation effects, agree reasonably well with the measured data.

We demonstrate that the effect of detection limits in the X-ray fluorescence analysis (XRF), which limits the determination of very low concentrations of trace elements and results in appearance of the so-called “nondetects”, can be accounted for using the statistical concept of censoring. More precisely, the results of such measurements can be viewed as the left random censored data, which can further be analyzed using the Kaplan–Meier method correcting the data for the presence of nondetects. Using this approach, the results of measured, detection limit censored concentrations can be interpreted in a nonparametric manner including the correction for the nondetects, i.e. the measurements in which the concentrations were found to be below the actual detection limits. Moreover, using the Monte Carlo simulation technique we show that by using the Kaplan–Meier approach the corrected mean concentrations for a population of the samples can be estimated within a few percent uncertainties with respect of the simulated, uncensored data. This practically means that the final uncertainties of estimated mean values are limited in fact by the number of studied samples and not by the correction procedure itself. The discussed random-left censoring approach was applied to analyze the XRF detection-limit-censored concentration measurements of trace elements in biomedical samples.

In the present paper, which follows our earlier observation that the asymmetric and long-tailed concentration distributions of trace elements in biomedical samples, measured by the X-ray fluorescence techniques, can be modeled by the log-stable distributions, further specific aspects of this observation are discussed. First, we demonstrate that, typically, for a quite substantial fraction (10–20%) of trace elements studied in different kinds of biomedical samples, the measured concentration distributions are described in fact by the “symmetric” log-stable distributions, i.e. the asymmetric distributions which are described by the symmetric stable distributions. This observation is, in fact, expected for the random multiplicative process, which models the concentration distributions of trace elements in the biomedical samples. The log-stable nature of concentration distribution of trace elements results in several problems of statistical nature, which have to be addressed in XRF data analysis practice. Consequently, in the present paper, the following problems, namely, (i) the estimation of parameters for stable distributions and (ii) the testing of the log-stable nature of the concentration distribution by using the Anderson–Darling (A2) test, especially for symmetric stable distributions, are discussed in detail. In particular, the maximum likelihood estimation and Monte Carlo simulation techniques were used, respectively, for estimation of stable distribution parameters and calculation of the critical values for the Anderson–Darling test. The discussed ideas are exemplified by the results of the study of trace element concentration distributions in selected biomedical samples, which were obtained by using the X-ray fluorescence (XRF, TXRF) methods.

It is shown that the detection limits in the total-reflection X-ray fluorescence (TXRF), which restrict quantification of very low concentrations of trace elements in the samples, can be accounted for using the statistical concept of censoring. We demonstrate that the incomplete TXRF measurements containing the so-called “nondetects”, i.e. the non-measured concentrations falling below the detection limits and represented by the estimated detection limit values, can be viewed as the left random-censored data, which can be further analyzed using the Kaplan–Meier (KM) method correcting for nondetects. Within this approach, which uses the Kaplan–Meier product-limit estimator to obtain the cumulative distribution function corrected for the nondetects, the mean value and median of the detection limit censored concentrations can be estimated in a non-parametric way. The Monte Carlo simulations performed show that the Kaplan–Meier approach yields highly accurate estimates for the mean and median concentrations, being within a few percent with respect to the simulated, uncensored data. This means that the uncertainties of KM estimated mean value and median are limited in fact only by the number of studied samples and not by the applied correction procedure for nondetects itself. On the other hand, it is observed that, in case when the concentration of a given element is not measured in all the samples, simple approaches to estimate a mean concentration value from the data yield erroneous, systematically biased results. The discussed random-left censoring approach was applied to analyze the TXRF detection-limit-censored concentration measurements of trace elements in biomedical samples. We emphasize that the Kaplan–Meier approach allows one to estimate the mean concentrations being substantially below the mean level of detection limits. Consequently, this approach gives a new access to lower the effective detection limits for TXRF method, which is of prime interest for investigation of metallic impurities on the silicon wafers.

Application of the total-reflection X-ray fluorescence (TXRF) analysis in the studies of trace element contents in biomedical samples is discussed in the following aspects: (i) a nature of trace element concentration distributions, (ii) censoring approach to the detection limits, and (iii) a comparison of two sets of censored data. The paper summarizes the recent results achieved in this topics, in particular, the lognormal, or more general logstable, nature of concentration distribution of trace elements, the random left-censoring and the Kaplan–Meier approach accounting for detection limits and, finally, the application of the logrank test to compare the censored concentrations measured for two groups. These new aspects, which are of importance for applications of the TXRF in different fields, are discussed here in the context of TXRF studies of trace element in various samples of medical interest.

The quantitative aspects of a use of random left-censoring as a statistical approach accounting for the detection limit effects in x-ray fluorescence (XRF) analysis were investigated using the Monte Carlo simulations. More precisely, the performance of the Kaplan-Meier method applied to the estimation of the original concentration distributions from detection limit censored concentration measurements are discussed. The simulations were performed for assumed log-normal and log-stable concentration distributions, which are known to model fairly well both concentrations and detection limits for biomedical and environmental samples. In particular, the question of the accuracy of the estimation of the mean value and median for the discussed concentration distributions using the Kaplan-Meier estimator was addressed. It is demonstrated that both the mean value and median of the concentration distribution can be estimated from censored data fairly precisely, typically within 4% for the log-normal and within 15% for log-stable models, even for substantial censoring levels (up to 80%). Moreover, the estimation of the median is much more precise than that of the mean value, in particular for stable distributions. Finally, the simulations show that random left-censoring can be recommended as a standard tool for analysing the detection limit censored concentration measurements of trace elements in XRF analysis.

The use of x-ray fluorescence techniques (XRF, TXRF, μXRF) in studies of trace element concentrations is limited by the detection limits (DL) of these methods. In this work we demonstrate that concentration measurements below the DL level, the so-called 'non-detects', can be included in data analysis by using the statistical concept of 'censoring', which is widely used, for instance, in survival analysis. This paper describes the non-parametric methods of analysis of censored data using the random left-censoring formalism, which can be used to account for the detection limits in XRF analysis. In particular, the application of the Kaplan-Meier and Nelson-Aalen estimators for the estimation of concentration distributions under censoring is discussed. These approaches are compared with the 'reconstruction method' developed earlier in our group to correct XRF data for the effect of detection limits. By using Monte Carlo simulations, the accuracy of the Kaplan-Meier and Nelson-Aalen estimators for censored data is discussed, in particular in the context of the estimation of the mean value and median of a concentration distribution. We demonstrate that for the 'two-group' comparison of left-censored concentrations, which is a problem of great practical importance, the log-rank test can be used. The idea of random left censoring is applied to analyse the TXRF detection limit-censored measurements of the concentrations of trace elements in biomedical samples.

The high-resolution spectra of thorium Mα 1,2 (M 5 N 6,7 ) and Mβ(M 4 N 6 ) X-ray lines induced by O and Ne ions with energies 376 and 178 MeV, respectively, have been measured using a von Hamos crystal spectrometer. The measured spectra exhibit the pronounced X-ray satellite structure due to the multiple ionization in the N- and M-shells. In particular the N-shell satellites are well resolved and the M-shell hypersatellites are clearly observed, to the best of our knowledge, for the first time. The observed M-X-ray diagram transitions and their satellites are interpreted using the multi-configuration Dirac-Fock (MCDF) calculations performed for the multi-vacancy configurations including up to two spectator vacancies. The comparison shows that calculations for more vacancies are needed to reproduce the measured X-ray structure. On the other hand, the data are well interpreted qualitatively using a simplified model of the “average” MCDF satellites having binomially distributed intensities. Further MCDF calculations are in the progress, which ultimately allow to extract precise (∼0.5 eV) information on the electronic structure of the multiple ionized thorium.