Lα Line Research Articles

Perturbation on atomic alignment of Ag L3-subshell by multiple ionization for heavy ions impact

Alignment of silver ion after electron in L3-subshell ionized by 1H+, 4He2+, 40Ar12+ and 129Xe30+ ions impact respectively are reported. Low incident energy range is investigated to explore collision-induced alignment in case of strong Coulomb deflection effect. Characteristic L X-ray spectra are measured in emission angle range of 115∘-155∘. For Lα and Lβ2 lines, anisotropy parameter β is determined respectively and then converted to degree of alignment A20 by taking anisotropy coefficient α and Coster-Kronig (CK) correction coefficient κ into account. The measured atomic alignment is compared to theoretical prediction basing on semiclassical model and satisfactory agreement is observed only for light ions impact. While the dealignment coefficient is determined to be 0.98, 0.71 and 0.30 for 4He2+, 40Ar12+ and 129Xe30+ ions impact at (vp/vL3)2=0.011, respectively. This work demonstrates the strong dealignment due to multiple ionization for heavy ions impact even in ultra low incident energy regime.

Feasibility for early cancer diagnostics by machine learning enabled synchrotron radiation based micro X-ray fluorescence imaging of trace biometals as cancer biomarkers

Trace quantitative spectroscopic imaging has the potential to provide the location and distribution of trace biometals in a biological sample for disease (cancer) diagnostics. However, spatial qualitative analysis of the trace biometals for cancer diagnostics remains a challenge due to the complex biological matrices that result in weak analyte signals and intricate multivariate relationships between the analyte spatial distribution and disease (cancer) state. In this study, principal component analysis (PCA)-enabled artificial neural networks (ANN) for micro X-ray fluorescence for simultaneous determination of biometal (Mn, Fe, Cu and Se) spatial profiles as biomarkers for cancer diagnosis in model human cell cultures (DU145 and Vero). The cell lines were cultured on silicon nitride membranes and micro XRF analysis carried out at TwinMic beamline, Elletra synchrotron source at beam excitation energy of 1.7 keV. These enabled 2D mapping of Mn, Fe, Cu and Se using cylindrical beam dimensions of Æ690 nm in stepper motor-controlled step sizes of 0.6μm with dwell times of 10s per pixel. Python multichannel analyzer (PyMca) software was used for spectral deconvolution and determination of 2D maps of the trace biometals. Principal component analysis (PCA) reduced the data dimensions for optimal artificial neural networks (ANN) exploratory modelling of cancer pathogenesis stages utilizing the pixel spectral profile of the trace biometals (Mn, Fe, Cu, Se). The 2D spatial distribution maps of the trace biometals revealed high spatial correlations between Cu and Fe ((0.941) and (0.923)) in DU_D3 and DU_D4 in cancerous compared to normal cell culture stages (V_D3 and V_D4) at 0.661 and 0.203 respectively. Utilizing PC1 and PC2 scores from selected fluorescence L (Lα and Lβ) lines of Fe and Cu, ANN distinctively classified the cell cultures into cancerous and healthy groups. Further, the selected fluorescence L-lines of Fe, Cu and Compton scatter spectral profiles enabled ANN classification of cancerous cultured cells into early, intermediate and advanced stages. The study has provided proof of concept for early diagnosis of cancer based on the multivariate alterations and spatial distribution of the trace biometals as cancer biomarkers.

Depth profiling of AlN and AlxGa1−xN crystals by XPS using Al Kα and Ag Lα line excitation and Ar ion gas cluster ion source

AlGaN-based heterostructures are promising candidates for the fabrication of ultraviolet light-emitting diodes. The analysis of the atomic composition of the grown epitaxial films is important from a technological point of view, allowing precise control over the wavelength and intensity of the emitted light. In this work, the depth profiling of AlN(0001), AlGaN(0001), and AlGaN quantum dot surfaces grown by molecular beam epitaxy was carried out by using angle-resolved x-ray photoelectron spectroscopy (XPS) combined with Ar gas cluster ion source (GCIS) sputtering. Core level shifts in XPS spectra measured by Al Kα and Ag Lα photon sources were determined. We found that sputtering by Ar1000+ ion clusters with an energy of 10 keV creates disorder on the surface and induces changes in surface atomic composition. As a result, depth profiling with a typical surface-sensitive Al Kα photon source is affected by the damaged layer. The application of a less surface-sensitive Ag Lα photon source with high photon energy could suppress the contribution from the damaged surface layer. Combining GCIS sputtering with Ag Lα line XPS measurements is, therefore, very promising for the quantification of atomic composition in the buried epitaxial layers or heterostructures with thicknesses of several tens of nm.

Total-reflection X-ray fluorescence determination of thorium and uranium in the presence of interfering elements in solid geological objects of natural and technogenic origin

The insufficient spectral resolution of the energy-dispersive total-reflection X-ray fluorescence (TXRF) complicates the U and Th Lα lines using for the quantitative determination of low concentrations of these elements in natural solid samples.

Collision-induced atomic alignment of silver after [formula omitted] ionization by 10–50 keV electron impact: Influence of Coster–Kronig transition effect

This work reports atomic alignment of silver after L3-subshell ionization in collisions with electrons in energy range 10–50 keV, i.e., (3∼15)EL3, where EL3(=3.351 keV) is the binding energy of electrons in the L3-subshell. The characteristic spectra are measured at different emission angles from -40∘ to 40∘ intervals of 10∘. The angular dependence of X-ray emission is studied for Lα(L3→M4,5) and Lβ2(L3→N5) lines respectively, using a thin target. The anisotropy parameter β is determined from two angular distribution measurements of differential X-ray intensity ratios dI(Lα,θ)/dI(Lβ1,θ) and dI(Lβ2,θ)/dI(Lβ1,θ). This served to reduce the experimental uncertainties. For the derivation of the alignment factor A20 we took into account the Coster–Kronig (CK) correction factor κ, which allows for, CK transition probabilities fij among L-subshells. We found that the sign of A20 is mostly negative, and the influence of CK transition is significant for large alignment parameters. In addition, the experimental results are compared to theoretical predictions within the framework of Plane Wave Born Approximation (PWBA) and reasonable agreement is found in the energy range studied in the present work. Simultaneously, good scaling property of atomic alignment is demonstrated when we consider also previous experimental results. Our measurement extends the scaled velocity V (=vp/vt) to a range of 1∼4 for medium-Zt targets, and the results of atomic alignment can provide a fundamental testing ground for ionization models.

Research and creation of broadband X-ray mirrors with a spectral transmission band coinciding with emission lines and the possibility of filtering

The article considers broadband multilayer X-ray mirrors based on Mo/Be and Mo/Si structures with a transmission band coinciding with the Si Lα (13.5 nm) and Sn (13.5 nm) emission lines. The described structures are of great interest for the currently developed liquid source of EUV radiation, since they make it possible to increase the efficiency of the source-X-ray optical system due to the "complete" capture of emission lines. Keywords: extreme ultraviolet radiation, emission spectrum, laser spark, multilayer X-ray mirror.

Исследование и создание широкополосных рентгеновских зеркал со спектральной полосой пропускания, совпадающей с эмиссионными линиями и возможностью фильтрации

The article considers broadband multilayer X-ray mirrors based on Mo/Be and Mo/Si structures with a transmission band coinciding with the Si Lα (13.5 nm) and Sn (13.5 nm) emission lines. The described structures are of great interest for the currently developed liquid source of EUV radiation, since they make it possible to increase the efficiency of the source-X-ray optical system due to the “complete” capture of emission lines.

Solving the iron quantification problem in low-kV EPMA: An essential step toward improved analytical spatial resolution in electron probe microanalysis—Fe-sulfides

Abstract The use of the field emission gun in scanning electron microscopy permits the imaging of submicrometer-size features. However, achieving sub-micrometer analytical spatial resolution in electron probe microanalysis (EPMA) requires both reducing the electron beam size and reducing the accelerating voltage to achieve the desired sub-micrometer interaction volume. The resulting quantification of the first-row transition metals at low accelerating voltage, i.e., below 7–8 kV, is problematic as the main characteristic X-ray lines (Kα) cannot be excited at these conditions. Furthermore, the use of the Lα and Lβ soft X-ray lines for quantification is complicated by bonding and self-absorption effects resulting in not-yet-determined mass absorption coefficients and hence in the failure of the traditional matrix correction procedure. We propose two methods to circumvent these low-kilovolt (low-kV) analysis limitations: using the non-traditional FeLℓ line and using universal calibration curves for the more traditional FeLα and Lβ lines. These methods were successfully applied to Fe-sulfide minerals showing accurate quantification results by EPMA at reduced kV, necessary for accurate quantification of sub-micrometer sulfide grains.

Tuneable in-situ nanoCT workflow using FIB/SEM

Inspired by the standard computed tomography, a new method of 3D X-ray imaging embedded in FIB-SEM microscope is proposed. The unique combination of TEM-like specimen stage enabling in lens STEM detection (referred to as CompuStage), nanomanipulator (referred to as EasyLift) facilitating in-situ sample transfer from bulk sample to TEM-like stage and pixelated in-situ Timepix X-ray detector in Helios G4 FX FIB-SEM system offers an unprecedented workflow. Motivated by common circular CT scan known from microCT world, the object under study is placed on CompuStage rod which enables two possible rotation (in TEM/SEM terminology called tilt) movements – α-tilt – rotation of the CompuStage rod around its axis, and β-tilt – rotation around axis perpendicular to CompuStage rod. β-tilt rotation enables a circular movement of the sample while α-tilt sets the correct position of sample with respect to target and detector. Thin metal lamella of suitable material welded to EasyLift manipulator needle is used as an X-ray target. The final target-sample geometry – position, distance – can be fine-tuned using position control of CompuStage and EasyLift and in-situ monitored by SEM. Both sample and target can also be easily prepared in-situ. Radiographs are recorded by Timepix detector with inherent noise-free operation and energy filtration. For the 3D reconstruction standard microCT reconstruction algorithm is used with the procedure adjusted for the format and quality of nanoCT images.The experiments were carried out on Helios G4 FX DualBeam using titanium and tungsten targets and various semiconductor samples. The ultimate resolution of the proposed method in orders of tens of nanometers was achieved both by the possibility of close target to sample positioning and of adjustment of primary beam energy down to low energies reducing the interaction volume in the target. Since the lower energy radiation is well suited for life-science, the method was also tested on several bio-samples using silver target. The silver target, thanks to its massive low energy Lα line, allowed to distinguish subtle structures in the resin embedded stained mouse brain and also to observe and reconstruct canaliculi in the mouse bone (earlier reported by Dierolf et al. 2010, Nature 467 436).

Impact Energy and Angular Dependence of L X-ray Emission from a Thick Polycrystalline Tungsten Element Induced by 15–25 keV Electrons

The impact energy and angular dependence of L X-rays of a thick polycrystalline tungsten (W; atomic number, Z = 74) target induced by 15–25 keV electrons has been measured at different angles varying from 15° to 75° at intervals of 5° using a Si PIN photodiode detector. The variation of measured relative intensity of Ll, Lα, Lβ and Lγ characteristic lines as a function of incidence angle is found to be anisotropic and the measured variation compares well with the PENELOPE simulation results. The angular variation of intensity ratio of Ll/Lα and Lβ/Lα shows anisotropic distribution, whereas the angular variation of the Lγ/Lα ratio exhibits almost isotropic distribution within the uncertainty of measurements. These measured ratios are found to be in good agreement with Monte Carlo (MC) calculations. The measured intensity ratios of Lβ/Lα and Lγ/Lα at a given incidence angle show a linear dependence with impact energy and exhibit good agreement with simulation results; however, the measured intensity ratio of Ll/Lα shows a non-linear variation with the impact energy and yields poor agreement with theoretical calculations.

L3-subshell alignment of Ag in collision with 15 keV electrons.

It is of great importance to study the alignment of atoms in collision process in elementary analysis with a Particle Induced X-ray Emission (PIXE) technique. The measurement of alignment can also offer an effective testing ground for developing theory models in ionization process. The typical L X-ray spectra are measured for Ag thin target by 15 keV electron impact at emission angles from 0° to 25°. Angular dependence of intensity ratios Lα/Lβ1, Lβ2/Lβ1 and Lγ/Lβ1 are investigated as a function of the second-order Legendre polynomial P2(cosθ). This study found that Lβ2 line exhibits anisotropic emission spatially, while the emission of Lα, Lβ1 and Lγ1 lines is isotropic. The results are interpreted by the influence of the Coster-Kronig (CK) transitions on the spatial distribution of X-ray emission. The anisotropy parameter β for Lβ2 lines is obtained experimentally and consequently the alignment degree A20 for L3 subshell is determined by taking CK transition into account. Namely, the alignment does exist in L3-subshell for atomic ionization by electron impact. The measurements offer an evidence to the existence of alignment for atomic ionization in electron-impact process.

Total reflection X-ray fluorescence analysis of uranium in the presence of competing elements☆

The analysis of uranium in environmental samples, quantified using total reflection X-ray fluorescence (TXRF) analysis, would be adversely affected by the presence of rubidium and strontium in larger amounts than uranium as coexisting elements. This is because the U Lα line at 13.61 keV is close to the Rb Kα line at 13.40 keV and the Sr Kα line at 14.17 keV. Using the U Lβ1 line (instead of the U Lα line), which does not overlap with the peaks of coexisting elements, we will be able to avoid these adverse effects. Since there is no TXRF device that can perform a quantitative analysis of uranium by using the U Lβ1 line, the following modifications were made to the existing device with the intention of rapid on-site analysis. The X-ray tube of the new device has a silver anode instead of a tungsten anode, and the sensitive area of the detector was expanded. In addition, the mechanism for adjusting the position of the sample stage was changed from manual to computerized control. These changes made it possible to screen uranium in environmental samples rapidly on site without chemical separation.

Using Calibration Curves to Quantify Fe with the Soft Lα and Lβ X-ray Lines

Using Calibration Curves to Quantify Fe with the Soft Lα and Lβ X-ray Lines

Quantitative Microanalysis of Chromites and Garnets at Low kV Using Fe and Cr Lα and Lβ X-ray Lines

Quantitative Microanalysis of Chromites and Garnets at Low kV Using Fe and Cr Lα and Lβ X-ray Lines

Determination of sulfur in Soils and Stream Sediments by Wavelength Dispersive X-ray Fluorescence Spectrometry

A simple, rapid and nondestructive wavelength dispersive X-ray fluorescence spectrometry (WD-XRF) was developed for the determination of sulfur in soils and stream sediments. WD-XRF was used to study the spectral line shifts and matrix effects of different inorganic species such as sulfide, elemental sulfur, thiosulfate, sulfite and sulfate. Analysis of the spectral lines in the S Kα wavelength range confirmed that Mo Lα (2θ = 111.799 °) lines interfered with S Kα (2θ=110.683°) lines. Twenty-seven soils and stream sediments reference samples were used to calibrate and evaluate the analytical method and the detection limit for sulfur was 5.43 mg/kg. The relative error (%RE) of the reference samples was −8.3–6.4%, showing good accuracy. However, the single form of sulfur (sulfide, sulfite and sulfate) had a significant matrix enhancement effect in the sodium carbonate matrix, especially for sulfides, and its relative error was 11.9 ~ 26.9%. The results of WD-XRF, inductively coupled plasma emission spectroscopy (ICP-OES) and elemental infrared analyzer were compared. The fitness for purpose of the results was also evaluated by the quality criteria test proposed by the International Geological Correlation Programme (IGCP), from which it can be deduced that the method was adequate considering geochemical mapping application.

Experimental and theoretical L-shell ionization cross sections of heavy atoms by impact of Si ions

We present a theoretical and experimental study of the subshell resolved L-shell ionization of relativistic targets such as 73Ta, 78Pt, 90Th, and 92U. The measurements of x-ray production cross sections by (84–140 MeV) Si+q ions (q = 8; 12), were held at the Inter-University Accelerator Centre of New Delhi. Multiple-hole fluorescence and Coster-Kronig yields were used to obtain the Li(i = 1–3) ionization cross sections from the measured x-ray production cross sections of Lℓ, Lα, and Lβ, Lη, and Lγ lines. The experimental results are compared with ab initio theoretical calculations by means of the shell-wise local plasma approximation (SLPA). This model uses the quantum dielectric formalism to obtain the total ionization cross sections from an initial ground state. The wave functions and binding energies of the different targets were obtained by solving the fully relativistic Dirac equation using the HULLAC code package. These calculations are based on first order perturbation theory with a central field, including Breit interaction and quantum electrodynamics corrections. The present SLPA ionization cross sections of the L-shell are found to be independent of the charge state of the Si ions. The experimental observations display also quite similar character if the correct mean projectile charge state inside the target is used for including the multiple ionization effect during ion-solid collisions. A general good agreement between the experimental measurements and full theoretical calculations supports the reliability of present results. The comparison also includes the well-known ECPSSR and ECUSAR semi empirical approximations. We noted that the ECUSAR results agree well with the SLPA, while the ECPSSR cross sections are rather low.

Absorption‐free calibration on X‐ray fluorescence analysis of high‐speed steel with glass bead preparation

This article describes a novel idea on preparation of a glass bead for X‐ray fluorescence spectrometry, to determine alloyed elements in high‐speed steel without any matrix correction. The quantification method using the glass bead is generally effective to reduce secondary X‐ray absorption and enhancement (matrix effect) by coexisting elements in a sample. Although the glass bead is normally prepared based on a flux‐to‐sample ratio, the suggested method mainly controls an absolute amount of the sample in the glass bead to prevent from any interference with the matrix elements. As a result, the alloyed elements, except tungsten, in high‐speed steels could be determined with high precision and accuracy, independent of the flux‐to‐sample ratio. However, the fluorescent X‐ray intensity of tungsten Lα line (8.40 keV) was obviously influenced by the sample amount (iron content) in a glass bead; in this case, the Mα line (1.77 keV) could be employed alternatively.

X-ray Lines in Binary Star Systems and the 3.55-keV Anomaly

A close binary star system that consists of a red giant and a neutron star is considered. X-ray emission from H-like Si XIV emerges during its recombination in the magnetic column of a neutron star with a superstrong magnetic field. The Lα Si XIV line with an energy of 3.55 keV is formed in a magnetic field of 6 × 1022 G. The identification of this line in the X-ray spectrum is discussed. The detection of Lα emission features during the recombination of such ions as C VI, N VII, O VIII, Ne X, Mg XII, S XVI, Ca XX, and Fe XXVI is predicted at energies both below and above 3.55 keV. A table for the energies in the Lα line for these ions in magnetic fields from 4 × 1012 to 1013 G is presented. The presence of anisotropy in the line emission is emphasized. It is shown that the realization of a recombination laser is possible and, as a consequence, the detection of these X-ray features up to redshifts z ≤ 100 is probable, although this will already be the ultraviolet range. It is noted that in the presence of a laser, line narrowing is inevitable.

Structure of high resolution Lα and Lβ1 x-ray emission spectra of 38Sr compounds

The recent advances in the instrumental operating detection system provide better understanding of the several atomic parameters such as characteristic x-ray emission lines, relative intensity ratio and line-width, transition probabilities, Coster-Kronig transitions and fluorescence yields. At present, the qualitative and quantitative analysis in wavelength dispersive spectrometers are routinely performed by the fundamental parameter approach method, but none of the approaches have been implemented in the routine analysis to test the possible influence of chemical effects in different chemical compounds. The study of chemical effects with high resolution curved crystals offers a great opportunity to enhance the analytical potential of WDXRF instruments. In the present work, high resolution Lα and Lβ1 emission spectra of 38Sr compounds have been measured with wavelength dispersive spectrometer. First time, spectral structures correlated to the satellite lines and their energy shifts are determined. In Lα energy region, three satellite peaks (Lα′, Lα″ and Lα‴) and in Lβ1 region, two satellite peaks (Lβ1′ and Lβ1″) are observed. To confirm the origin of the satellite peaks associated with each of the Lα and Lβ1 diagram lines, we have calculated the theoretical values of energies by using available Hartree-Fock-Slater approximation based on K-LM and L-MN Auger transition energies. The measured and calculated values of the satellite peak energies are found in good agreement with each other. The possible causes of energy shifts such as Coster-Kronig transitions, effective charge, relative intensity ratio and line-width, screening effect, shake process and electro-negativity and their roles in different 38Sr compounds are also discussed.

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

This work was aimed to improve the instrumental detection limit and sensitivity of 17Cl, 37Rb, and 38Sr elements present in solid samples by using the advanced polychromatic wavelength dispersive X-ray fluorescence spectrometry method. Instrumental measuring parameters, as well as study of calibration curves of K and L shell spectral lines, were evaluated to select the best conditions for 17Cl, 37Rb, and 38Sr quantification. From the results, it was observed that the detection limits of the Rb Kα and Sr Kα spectral lines were lower than those of the Kβ1,3 and Lα spectral lines. From the calibration curves, it was concluded that Kα spectral lines are more suitable than Kβ1,3 and Lα lines to identify the traces of 17Cl, 37Rb, and 38Sr elements in different types of solid samples.