Search

• Nanostructure of SnO 2 doped with Fe ions were synthesized through co-precipitation method. • XRD pattern infer the single phase nature of Fe doped SnO 2 nanoparticles. • Band gap engineering of Fe doped SnO 2 nanoparticles. • NEXAFS study infers that Fe in mixed valence state. This paper presents the electronic structure and optical behavior of Sn 1-x Fe x O 2 (0 % ≤ x ≤ 7 %) nanoparticles synthesized using co-precipitation assisted hydrothermal method. The structural properties of as-synthesized nanoparticles were examined using XRD and Raman spectroscopy. The XRD results demonstrated that all the samples are crystallized in tetragonal (rutile) crystal structure without any hint of impurity phase. The crystallite sizes measured using XRD spectra were found to vary from 7.0 to 10.0 nm. The effect of Fe doping and local defects were identified via surface-enhanced Raman spectroscopy (SERS). The local electronic structure was studied using NEXAFS at Fe L 3, 2 , O K edges which demonstrate that Fe ions are situated at the Sn sites with Fe3+ (pre-dominant) and Fe2+ (minor) mixed valance states. The octahedral (O h) ligand field split the Fe (3d) state into t 2g and e g states with ∼ 3 eV energy splitting. The optical properties were explored by using UV–vis spectra, which reveals transparent behavior in the visible light region and good absorption in the ultraviolet range. The asymmetrical change in the bandgap energy (3.6–3.1 eV) with the variation in Fe dopant level may be due to the casual distribution of Fe ions inside the host SnO 2 crystal texture. [ABSTRACT FROM AUTHOR]

We investigate in the present paper the doubly excited 1 P o states in the C 4 + ion. We report highly accurate results of their energy positions in the energy spectrum, their lifetimes and the x-ray photon energies required to populate them and observe their autoionization. The results were obtained by using our B-spline based spectral approach combined with the complex rotation method that has proven its effectiveness in the detection of the doubly excited states in the O 6 + [1] and Li + [2] ions. We also report in the paper the first results on the characterization and identification of the states that share similar angular correlation pattern, which allows their classification into distinct resonance series. • Accurate spectral approach to describe the 1P0 resonance series in the C4+ ion. • Precise x-ray photon energies required to populate the doubly excited states. • Precise resonance energies and lifetimes of the doubly excited states. • First results on the classification of the states into distinct resonance series. [ABSTRACT FROM AUTHOR]

The application of a potential model to the analysis of differences between the Auger parameters of InSb and the elemental materials yields a value 1.82 ± 0.07 Å for the core hole screening distance in InSb. It also yields a value of 0.22 ± 0.49 e for the charge transfer in InSb. Shifts in the Auger parameters of elements between their metallic states and in a compound semiconductor are interpreted using a novel method based on quantifying atomic core potential, as a quantum mechanical observable, in terms of its dependence on the valence charge and the number of atomic core holes. The core hole screening distance is ∼ 30 % larger than half the interatomic distance between the nearest neighbors and, by the equivalent cores model, is expected to be the screening radius of Sn and Te impurities in InSb. • The main achievement of this paper is to determine the core hole screening distance in InSb. • The paper shows this has a value of 1.82 ± 0.07 Å. • The paper also establishes a method of determining charge transfer in semiconductors though the accuracy of this determination is rather poor: 0.22 ± 0.49 e. [ABSTRACT FROM AUTHOR]

Highlights • Automated as-is analysis of insulating samples utilizing standalone NAP XPS system. • Environmental Charge Compensation for charge neutralization in NAP XPS. • NAP XPS intrinsic charge compensation on polymers and commercial products. Abstract X-ray photoelectron spectroscopy (XPS) has become a routine analysis method to determine the chemical composition and bonding states of elements of sample surfaces in many industrial applications, like materials development, failure analysis, quality control and device certification. To obtain significant results the analyses of such samples require a fast analysis with reliable quantification and stable data for repeated experiments. In standard XPS experiments under ultrahigh vacuum (UHV) conditions the significance of the results can be affected by changing surface compositions under the analysis conditions, different degrees of degassing and thus changing degrees of differential charging in insulating samples. In this publication the positive influence of XPS analysis under elevated pressures, often named Near-Ambient Pressure XPS or "Environmental XPS" is shown for different samples. Furthermore the process of charge compensation in gas pressures of 1–2 mbar is introduced, followed by a discussion of the perspectives of this "Environmental Charge Compensation". The paper discusses the efficiency and stability of Environmental Charge Compensations for typical insulating test samples, as well as for different bulk insulators. The additional capability of XPS in elevated pressures is demonstrated on a superabsorbent polymer typically used in diapers, showing the difference of the analysis results for its wet and dry state. The paper ends with the example of a commercial printed circuit board demonstrating the power of the method for routine analysis of complete devices. [ABSTRACT FROM AUTHOR]

Highlights • Detailed description of various industrial applications of XPS in India. • Elemental composition, chemical environment identification are primarily used. • Contains table of institutes in India with XPS spectrometers. • Contains table of industries that have used XPS in their research activities. Abstract This review paper summarizes the industrial applications of XPS in India from open literature. Many industrial research and development centers in India, except for a few, do not have in-house XPS systems, and leverage either the instruments available at many government laboratories or universities across various locations in India, or their in-house instruments in other parts of the world for their research activities. While XPS is being used for a wide range of applications, based on an exhaustive literature search by the author, an understanding of the scientific basis of the technique as well as related analytical techniques such as X-ray Excited Auger Electron Spectroscopy (XAES) and depth profiling, the instrumentation, the measurement, and interpretation of the results could be improved. This could potentially avoid artifacts as well as misinterpretation of results. This paper also highlights a few key points that must be considered while measuring and interpreting XPS data. [ABSTRACT FROM AUTHOR]

The development of solar fuel generating materials would greatly benefit from a molecular level understanding of the semiconductor/electrolyte interface and changes in the interface induced by an applied potential and illumination by solar light. Ambient pressure photoelectron spectroscopy techniques with both soft and hard X-rays, AP-XPS and AP-HAXPES respectively, have the potential to markedly contribute to this understanding. In this paper we initially provide two examples of current challenges in solar fuels material development that AP-XPS and AP-HAXPES can directly address. This will be followed by a brief description of the distinguishing and complementary characteristics of soft and hard X-ray AP-XPS and AP-HAXPES and best approaches to achieving monolayer sensitivity in solid/aqueous electrolyte studies. In particular we focus on the detection of surface adsorbed hydroxyl groups in the presence of aqueous hydroxide anions in the electrolyte, a common situation when investigating photoanodes for solar fuel generating applications. The paper concludes by providing an example of a combined AP-XPS and AP-HAXPES study of a semiconductor/aqueous electrolyte interface currently used in water splitting devices specifically the BiVO 4 /aqueous potassium phosphate electrolyte interface. [ABSTRACT FROM AUTHOR]

In this paper, we report an extensive theoretical study of the magnetic-field and hyperfine-induced transition parameters for magnesium-like ions from Cr XIII to Zn XIX and chlorine-like ions from Mn IX to Co XI. These ions have a high abundance in the astrophysical plasma. Zeeman splitting level energies, hyperfine- and/or magnetic-field dependent wavelengths, and transition rates of the 3s3p 3 P 2 , 1 , 0 → 3 s 2 1 S 0 (for magnesium-like ions) and the 3p43d 4 D 7 / 2 → 3p5 2 P 3 / 2 line (for chlorine-like ions), are computed using the multiconfiguration Dirac–Fock method. Some higher-order effects, such as the Breit interaction and quantum electrodynamics corrections, are included in the relativistic configuration interaction method, as this makes the results more accurate. A comparison between the our predictions and other theoretical and experimental values is made. A satisfactory agreement is achieved. Besides providing valuable information for spectral line analysis, the present work will have a variety of implications for fusion and astrophysical plasma sources, for example, in the determination of magnetic fields in solar coronas and other stars. • Magnetic-field and hyperfine-induced transition parameters for magnesium-like ions and chlorine-like ions are studied. • A comparison between the our predictions and other theoretical and experimental values is made. • This study has a variety of implications for fusion and astrophysical plasma sources. [ABSTRACT FROM AUTHOR]

This paper reviews our contributions and the development of an instrument for X-ray photoelectron diffraction (XPED) and X-ray holography. XPED and X-ray holography have been extensively applied in materials analysis over the past decades. We made pioneering contributions in this area that fueled the development of the corresponding instrumentation and technology. In this review, we briefly discuss the theory of XPED and X-ray holography instrument, the genesis, and applications. The instruments comprise a high-power soft and hard X-ray source as well as a diffraction aperture; further, they are capable of high-angular-resolution detection and patterning. The applications of these instruments for practical surface analysis are also reviewed for ultrathin insulators, catalysts, and magnetic materials. Finally, possibilities for the differential photoelectron holography (DPH) approach are premiered based on a novel approach. • This paper reviews our contributions and the development of instruments for XPED and X-ray holography over the last decades. • We demonstrated our original laboratory-level XPED instruments from the perspectives of a high-power soft and hard X-ray source, diffraction aperture, and high-angular-resolution detection. • We also demonstrated applications of practical surface analysis for ultrathin insulators, catalysts, and magnetic materials. • We premiered possibilities for differential photoelectron holography (DPH) based on the atomic reconstruction method using typical four-wave numbers. [ABSTRACT FROM AUTHOR]

• Calibrations and checks of the binding-energy scales of X-ray photoelectron spectrometers. • Recommended binding energies of photoelectron lines for 55 elemental solids. A recent paper in this journal [B. V. Crist, J. Electron Spectrosc. Relat. Phenom. (in press)] describes current and historical calibration problems with core-electron binding energies (BEs) measured by X-ray photoelectron spectrometers and how these problems affect BE data in databases. Although Crist provides useful information about the variability of reported BE values, his article is incomplete or incorrect in some historical and other details. The present article corrects and extends information in the Crist paper and provides additional information on how calibrations and checks of the BE scale should be made. [ABSTRACT FROM AUTHOR]

The recent development of high brightness 3 rd generation soft X-ray sources and high energy resolution electron spectrometers made it possible to accurately trace quantum phenomena associated to the vibrational dynamics in core-excited molecules. The present paper reviews the recent results on mapping of vibrational wave functions and molecular potentials based on electron spectroscopy. We discuss and compare the mapping phenomena in various systems, stressing the advantages of the resonant X-ray scattering for studying of the nuclear dynamics and spectroscopic constants of small molecules. The experimental results discussed in the paper are most often accompanied by state-of-the-art ab initio calculations allowing for a deeper understanding of the quantum effects. Besides its fundamental interest, the vibrational wave function mapping is shown to be useful for the analysis of core- and valence-excited molecular states based on the reflection principle. [ABSTRACT FROM AUTHOR]

Abstract: Thin-film solar cells based on compound semiconductors consist of a multilayer structure with various interfaces and contain a multitude of elements and impurities, etc. A rapid progress of these photovoltaic technologies can only be achieved by an insight-driven optimization/development. Hence it is crucial to characterize and understand the relationship between the chemical and electronic properties of these components. This paper reviews some examples of our recent work characterizing compound semiconductor thin films using laboratory- and synchrotron-based electron and soft X-ray spectroscopic characterization methods. It is demonstrated how these different analytical techniques are extraordinarily powerful to reveal the material characteristics from many different perspectives, ultimately resulting in a comprehensive picture of the related electronic and chemical properties. As examples, the paper will discuss the electronic surface structure of chalcopyrite thin-film solar cell absorbers, the chemical structure of the CdS/chalcopyrite interface, present the band alignment at the CdS/kesterite interface, and report on how post-deposition treatments cause chemical interaction/interdiffusion processes in CdTe/CdS thin-film solar cell structures. [Copyright &y& Elsevier]

The C 1s photoelectron spectrum of ethyl trifluoroacetate (CF3—CO—O—CH2—CH3), also known as the ‘ESCA molecule’, is the most illustrative showcase of chemical shifts in photoelectron spectroscopy. The binding energies of the four carbon atoms of this molecule spread over more than 8 eV with energy separations ranging from 1.7 to 3.1 eV owing to different chemical environments and hence different charge states of these atoms. The paper discusses history and importance of this spectrum in the field of photoelectron spectroscopy starting from the time of invention of the ESCA technique. The main focus of the paper is a ‘revisit’ of this spectrum using the most modern experimental and computational tools. Large geometrical changes, different for each ionization site, and the presence of two conformers of ethyl trifluoroacetate influence the spectral lineshapes of all four C 1s lines. These effects are carefully modeled by theory and investigated in the experimental spectrum. [Copyright &y& Elsevier]

In one of the papers, El-Maaref et al. [J. Elect. Spectrosc. Related Phen. 215 (2017) 22] have reported results for energy levels, oscillator strengths (f -values), radiative rates (A -values), collision strengths (Ω), and excitation rates for transitions in S-like Mn X. However, except for energy levels their results are restricted to only a few transitions and hence have limited application. Furthermore, most of their results have scope for improvement, but for Ω are not correct as these have been found to be overestimated by an order of magnitude. In this comment we discuss the discrepancies and deficiencies of their results and recommend that a fresh calculation should be performed for this ion. [ABSTRACT FROM AUTHOR]

• Surface contamination by airborne molecules influences the interfacial properties of graphitic materials. • UPS and orthogonal techniques have been applied to analyze the composition of airborne contaminants on HOPG. • Immediate surface contamination of HOPG upon exposure to air and the evolution of its composition over time can be resolved by UPS. This paper reports the surface chemistry of highly ordered pyrolytic graphite (HOPG) upon exposure to ambient air. Ultra-violet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) measurements were collected from freshly-cleaved HOPG in ultra-high vacuum and after exposure to ambient air. We observed an immediate surface contamination during exfoliation of HOPG in ambient air, which we attribute to functionalization of surface defects and step edges. Additional air exposures result in further growth of the contamination layer, as well as dynamic composition changes from more weakly bound to more strongly bound species over time. This work is the first to show the immediate contamination of graphite upon exfoliation in air and the dynamic exchange of surface contaminants over long exposure times. [ABSTRACT FROM AUTHOR]

• Halloysite nanotubes have many applications; a thermal pre-treatment is employed in many of them. • Thermal, structural and microstructural description was carried out up to 1400 °C. • Al- Near edge absorption spectroscopy (XANES) was employed for local structure. • Loss of crystalinity, tube morphology retention were observed. • A multiple Al-Coordination for Metahalloysite was determined. Halloysite and its heating products demand attention due to its multiple technological applications, and in particular for its natural nanostructure. The purpose of this paper is to present a structural characterization of these materials and its firing products up to mullite. To achieve this objective, the techniques of conventional X-ray diffraction (XRD) and X-ray absorption near-edge structure (XANES) were used, in addition to scanning electron microscopy (SEM), and simultaneous thermogravimetric and differential thermal analysis (DTA-TG). SEM has allowed to prove that the nanotubular morphology (acicular) of halloysite was retained for all temperatures (500, 800, 1100 and 1250 °C). For the temperatures between 500 and 800 °C the metahalloysite phase was identified. The 1100 °C fired samples presented the spinel aluminosilicate phase. Finally, after high temperature treatments the mullite phase was detected as the only aluminum containing crystalline phase accompanied by cristobalite and glassy phase. The XANES spectra confirmed the octahedral aluminum coordination in native halloysite, this coordination was progressively lost with the thermal treatments giving place to the presence of the four folded coordination. In the intermediate treatments, the so called metahalloysite phase, presented some three and five coordination slight contributions. Particularly, the metahalloysite Al K XANES spectra were not reported before. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The paper presents an original technique for quantitative analysis of the chemical composition from photoelectron lines obtained by X-ray photoelectron spectroscopy. Despite the simplicity, a proposed algorithm of spectral fit refinement allows one to control the fitting accuracy and to minimize the errors in determining the concentrations of chemical compounds. An obvious advantage of the iterative approach is the automatic convergence to the true spectrum fit form under correct input assumptions and conditions. The validity of the refinement technique is proved by the results of its application in the study of the chemical composition of three types of solid-state structures of nanoelectronics and spintronics. The error decrease in determining the concentration provides revealing new physicochemical features of the phase formation under various methods and parameters of the creation of structures. The discovered dependences of magnetic, electrical and optoelectronic properties on the local composition of nanosystems make it possible to formulate scientifically grounded principles of their development. Due to its simplicity and versatility, the spectral fit refinement technique can be extended to other experimental methods, where mathematical processing of spectral data is required. [ABSTRACT FROM AUTHOR]

Abstract: This paper examines the types of information that XPS can provide about a variety of nanostructured materials. Although it is sometimes not considered a “nanoscale analysis method,” XPS can provide a great deal of information about elemental distributions, layer or coating structure and thicknesses, surface functionality, and even particles sizes on the 1–20nm scale for sample types that may not be readily analyzed by other methods. This information is important for both synthetic nanostructured or nanosized materials and a variety of natural materials with nanostructure. Although the links between nanostructure materials and biological systems may not at first be obvious, many biological molecules and some organisms are the sizes of nanoparticles. The nanostructure of cells and microbes plays a significant role in how they interact with their environment. The interaction of biomolecules with nanoparticles is important for medical and toxicity studies. The interaction of biomolecules is important for sensor function and many nanomaterials are now the active elements in sensors. This paper first discusses how nanostructures influences XPS data as a part of understanding how simple models of sample structure and data analysis can be used to extract information about the physical and chemical structures of the materials being analyzed. Equally important, aspects of sample and analysis limitations and challenges associated with understanding nanostructured materials are indicated. Examples of the application of XPS to nanostructured and biological systems and materials are provided. [Copyright &y& Elsevier]

Abstract: Diffractive optics now plays a major role in optical systems for the extreme ultraviolet and X-ray region. For example, zone plates in their different appearances are widely used for focusing X-rays, as monochromatizing condenser optics, and for high resolution imaging, particularly in X-ray microscopy. The idea in this paper is based upon a more general approach to solve optical problems by transforming a given light distribution or wave as input into the desired waveform on the output of a single X-ray optical component. In this paper we present the design, fabrication and use of novel phase diffractive optical elements (DOEs) that, besides simple focusing, can perform new optical functions in the range of X-rays. Using our own code, we calculated and fabricated through e-beam and X-ray lithography high-resolution DOEs that can generate a constant intensity on a plane (top-hat DOE) or focus a monochromatic X-ray beam into multiple spots. The possibility to introduce a specified phase shift between the generated spots, which can increase the image contrast, is demonstrated by experimental results obtained from computer simulations and experiments performed between 3 and 7.2keV in both full-field and scanning X-ray microscopy at the ID21 beamline of the European Synchrotron Radiation Facility (ESRF). [Copyright &y& Elsevier]

The investigation of the peculiarities of the electron structure of invar alloys Fe50Mn50, Fe65Ni35, Co0.7(FeMn)0.3 and Co0.3(FeMn)0.7 is presented in the given paper. For this purpose, their X-ray photoelectron spectroscopy (XPS) spectra of core levels and valence bands have been studied with an X-ray electron magnetic spectrometer. Unusual aspects of the electronic structure of invar alloys were found. In this paper, it has been shown that the structure of the multiplet splitting of the 3s spectra of d-metals characterizes the nearest environment of metal atoms. Besides, based on the changes in the parameters of the multiplet splitting of the 3s-spectra of d-metals, we can make a conclusion about the changes taking place in localization of d-electron density and atomic magnetic moment. The investigation of the parameters of the 3s-spectra of invar alloys shows the existence of two states of Fe atoms occurring due to different nearest environments and magnitudes of atomic spin magnetic moment. When passing through Curie point (TC) some of atoms go from one magnetic state into the other, and the ratio of the amounts of Fe atoms in these states also changes. [Copyright &y& Elsevier]

In this paper we review a variety of spectra for Ce compounds, i.e. valence photoemission and inverse valence photoemission, core-level and resonant photoemission as well as X-ray absorption, X-ray emission and X-ray magnetic circular dichroism (MCD). Those spectra are theoretically analysed by using the single-site Anderson model with various final state interactions. In the first part of the present article we are considering intermetallic Ce compounds, especially several Ce–Pd ordered phases, as well as CeRh3, CeSn3 and CeFe2. In the second part we focus on insulating Ce compounds like CeF3 as well as related systems like Ce oxides. Also we compare Ce hydroxides to other rare-earth hydroxides. Discussions are given on the physical information derived from the analysis, especially through a few key parameters of an extended version of the previously considered Anderson model. Those parameters (i.e. the Coulomb interaction Ufd between 5d and 4f electrons as well as the core hole potential -Udc acting on the 5d electron) have necessarily to be taken into account in order to interpret the experimental L3 X-ray absorption spectra. Another important point stressed in the present paper is the surface/bulk sensitivities of the various spectra to be investigated and theoretically analysed. Also similarities and differences in spectral features between metallic and insulating systems are pointed out. [ABSTRACT FROM AUTHOR]

In this paper we review a variety of spectra for Ce compounds, i.e. valence photoemission and inverse valence photoemission, core-level and resonant photoemission as well as X-ray absorption, X-ray emission and X-ray magnetic circular dichroism (MCD). Those spectra are theoretically analysed by using the single-site Anderson model with various final state interactions. In the first part of the present article we are considering intermetallic Ce compounds, especially several Ce–Pd ordered phases, as well as CeRh3, CeSn3 and CeFe2. In the second part we focus on insulating Ce compounds like CeF3 as well as related systems like Ce oxides. Also we compare Ce hydroxides to other rare-earth hydroxides. Discussions are given on the physical information derived from the analysis, especially through a few key parameters of an extended version of the previously considered Anderson model. Those parameters (i.e. the Coulomb interaction Ufd between 5d and 4f electrons as well as the core hole potential -Udc acting on the 5d electron) have necessarily to be taken into account in order to interpret the experimental L3 X-ray absorption spectra. Another important point stressed in the present paper is the surface/bulk sensitivities of the various spectra to be investigated and theoretically analysed. Also similarities and differences in spectral features between metallic and insulating systems are pointed out. [ABSTRACT FROM AUTHOR]

In this paper we review a variety of spectra for Ce compounds, i.e. valence photoemission and inverse valence photoemission, core-level and resonant photoemission as well as X-ray absorption, X-ray emission and X-ray magnetic circular dichroism (MCD). Those spectra are theoretically analysed by using the single-site Anderson model with various final state interactions. In the first part of the present article we are considering intermetallic Ce compounds, especially several Ce–Pd ordered phases, as well as CeRh3, CeSn3 and CeFe2. In the second part we focus on insulating Ce compounds like CeF3 as well as related systems like Ce oxides. Also we compare Ce hydroxides to other rare-earth hydroxides. Discussions are given on the physical information derived from the analysis, especially through a few key parameters of an extended version of the previously considered Anderson model. Those parameters (i.e. the Coulomb interaction Ufd between 5d and 4f electrons as well as the core hole potential -Udc acting on the 5d electron) have necessarily to be taken into account in order to interpret the experimental L3 X-ray absorption spectra. Another important point stressed in the present paper is the surface/bulk sensitivities of the various spectra to be investigated and theoretically analysed. Also similarities and differences in spectral features between metallic and insulating systems are pointed out. [ABSTRACT FROM AUTHOR]

In this paper we review a variety of spectra for Ce compounds, i.e. valence photoemission and inverse valence photoemission, core-level and resonant photoemission as well as X-ray absorption, X-ray emission and X-ray magnetic circular dichroism (MCD). Those spectra are theoretically analysed by using the single-site Anderson model with various final state interactions. In the first part of the present article we are considering intermetallic Ce compounds, especially several Ce–Pd ordered phases, as well as CeRh3, CeSn3 and CeFe2. In the second part we focus on insulating Ce compounds like CeF3 as well as related systems like Ce oxides. Also we compare Ce hydroxides to other rare-earth hydroxides. Discussions are given on the physical information derived from the analysis, especially through a few key parameters of an extended version of the previously considered Anderson model. Those parameters (i.e. the Coulomb interaction Ufd between 5d and 4f electrons as well as the core hole potential -Udc acting on the 5d electron) have necessarily to be taken into account in order to interpret the experimental L3 X-ray absorption spectra. Another important point stressed in the present paper is the surface/bulk sensitivities of the various spectra to be investigated and theoretically analysed. Also similarities and differences in spectral features between metallic and insulating systems are pointed out. [ABSTRACT FROM AUTHOR]

In this paper we review a variety of spectra for Ce compounds, i.e. valence photoemission and inverse valence photoemission, core-level and resonant photoemission as well as X-ray absorption, X-ray emission and X-ray magnetic circular dichroism (MCD). Those spectra are theoretically analysed by using the single-site Anderson model with various final state interactions. In the first part of the present article we are considering intermetallic Ce compounds, especially several Ce–Pd ordered phases, as well as CeRh3, CeSn3 and CeFe2. In the second part we focus on insulating Ce compounds like CeF3 as well as related systems like Ce oxides. Also we compare Ce hydroxides to other rare-earth hydroxides. Discussions are given on the physical information derived from the analysis, especially through a few key parameters of an extended version of the previously considered Anderson model. Those parameters (i.e. the Coulomb interaction Ufd between 5d and 4f electrons as well as the core hole potential -Udc acting on the 5d electron) have necessarily to be taken into account in order to interpret the experimental L3 X-ray absorption spectra. Another important point stressed in the present paper is the surface/bulk sensitivities of the various spectra to be investigated and theoretically analysed. Also similarities and differences in spectral features between metallic and insulating systems are pointed out. [ABSTRACT FROM AUTHOR]

In this paper we review a variety of spectra for Ce compounds, i.e. valence photoemission and inverse valence photoemission, core-level and resonant photoemission as well as X-ray absorption, X-ray emission and X-ray magnetic circular dichroism (MCD). Those spectra are theoretically analysed by using the single-site Anderson model with various final state interactions. In the first part of the present article we are considering intermetallic Ce compounds, especially several Ce–Pd ordered phases, as well as CeRh3, CeSn3 and CeFe2. In the second part we focus on insulating Ce compounds like CeF3 as well as related systems like Ce oxides. Also we compare Ce hydroxides to other rare-earth hydroxides. Discussions are given on the physical information derived from the analysis, especially through a few key parameters of an extended version of the previously considered Anderson model. Those parameters (i.e. the Coulomb interaction Ufd between 5d and 4f electrons as well as the core hole potential -Udc acting on the 5d electron) have necessarily to be taken into account in order to interpret the experimental L3 X-ray absorption spectra. Another important point stressed in the present paper is the surface/bulk sensitivities of the various spectra to be investigated and theoretically analysed. Also similarities and differences in spectral features between metallic and insulating systems are pointed out. [ABSTRACT FROM AUTHOR]

In this paper we review a variety of spectra for Ce compounds, i.e. valence photoemission and inverse valence photoemission, core-level and resonant photoemission as well as X-ray absorption, X-ray emission and X-ray magnetic circular dichroism (MCD). Those spectra are theoretically analysed by using the single-site Anderson model with various final state interactions. In the first part of the present article we are considering intermetallic Ce compounds, especially several Ce–Pd ordered phases, as well as CeRh3, CeSn3 and CeFe2. In the second part we focus on insulating Ce compounds like CeF3 as well as related systems like Ce oxides. Also we compare Ce hydroxides to other rare-earth hydroxides. Discussions are given on the physical information derived from the analysis, especially through a few key parameters of an extended version of the previously considered Anderson model. Those parameters (i.e. the Coulomb interaction Ufd between 5d and 4f electrons as well as the core hole potential -Udc acting on the 5d electron) have necessarily to be taken into account in order to interpret the experimental L3 X-ray absorption spectra. Another important point stressed in the present paper is the surface/bulk sensitivities of the various spectra to be investigated and theoretically analysed. Also similarities and differences in spectral features between metallic and insulating systems are pointed out. [Copyright &y& Elsevier]

Photoemission electron microscopy (PEEM), particularly when combined with synchrotron radiation, exerts a powerful functionality in spectroscopy applications. The use of PEEM has steadily expanded the availed analysis objects at the SPring-8 synchrotron facility, such as magnetic materials, thin-film devices, semiconductors, monolayers, extraterrestrial matter, and multiferroics. Some special experimental settings such as time-resolved or operando measurements have also been developed according to user requests. In this paper, we present an overview on the achievements of PEEM studies so far and introduce some recent technical and scientific progress at SPring-8. • Studies done using photoemission microscopy (PEEM) at SPring-8 are comprehensively introduced with references. • Surface conductivity created by irradiation of strong synchrotron radiation X-rays are visualized by PEEM. • Trials for PEEM observations under magnetic fields are introduced. • Magnetic anisotropy of bulk Fe 50 Pd 50- x Ni x processed by high pressure torsion is investigated. [ABSTRACT FROM AUTHOR]

Spectroptychography is being used to realize a significant improvement in the spatial resolution of x-ray spectromicroscopy, allowing chemical microanalysis at finer spatial scales. The chemical sensitivity of near edge X-ray absorption fine structure (NEXAFS) is familiar to most researchers who use x-ray spectromicroscopy for chemical microanalysis. However, the additional phase information available through ptychography provides additional and tantalizing data, and potentially additional chemical information. This paper explores the chemical information available in phase for a system of silicon dioxide nanospheres. • Soft x-ray spectroptychography provides chemical information through absorption and phase. • Phase spectra reveal chemical information in an indirect manner. • The Kramers–Kronig relation is useful for understanding contrast in ptychography chemical analysis. [ABSTRACT FROM AUTHOR]

The spatially resolved ARPES (nanoARPES) is a development of conventional ARPES technique achieved with the focusing of light on the sample into the spot with submicron sizes. This development is used in research of essentially small samples, for example, heterostructures build of flakes of 2D materials, micro-crystals or polycrystalline samples, different crystal termination, domains in electronic structure. ANTARES is delivering the nanoARPES technique to user community since 2010, up to now the instrument was used with samples of various types, and that was useful to accumulate the specific experience. In this paper we report the current layout and actual performance of the ANTARES instrument at Synchrotron SOLEIL, as well as the most typical application areas. The most important and recent upgrades include focusing optics and in-operando setup. The new optical units deliver the increased flux on sample as well as the option to vary the photon energy. The in-operando setup offers the option of electrical connection to the sample being studied with nanoARPES, that promises various applications, where the most demanded now is the control of charge carrier density with applied voltage. This "gate-doping" is often applied to the heterostructures of 2D materials, that could be designed and build on purpose. The 2D heterostructures is probably the most typical field of application of the instrument, with or without in-operando option. At the same time the use case of the ANTARES instrument is still in the development by the realisation of new kinds of samples and of the new types of the experiments. • NanoARPES is a technique providing the angles resolved photoemission with spatial resolution. • ANTARES is a nanoARPES instrument launched about 10 years ago among the first instruments. • The instrument is delivering performance adequate for studies in various research areas. • Research of 2D materials and heterostructures, topological materials, superconductors, and other subjects. • In-operando electrical connections to the sample under measurement provides opportunity to study micro-devices. [ABSTRACT FROM AUTHOR]

In this paper, we give an overview of the nanoscale spectromicroscopy studies performed with the full-field X-ray microscope at the BESSY II electron storage ring. We do not consider spectromicroscopy studies performed with X-ray microscopes operated at other synchrotron sources. Such studies can be found in the literature. To our knowledge, the full-field X-ray microscope at the BESSY II storage ring is the first one operating with both a plane-grating-monochromator (PGM) beamline equipped with multi-layer optics for the tender X-ray range, as well as with standard optical elements for the soft X-ray range. We discuss how this instrument has been used in various published NEXAFS-TXM studies to probe low dimensional nanostructures. This research work paves the way for understanding electronic structures approaching the atomic scale, and will thereby help in the design of tailored functional systems. • Nanoscale X-ray spectromicroscopy with a full-field X-ray microscope. • Nanoscale oxides in catalysis and light harvesting/storage applications. • X-ray spectromicroscopy studies of microelectronic devices. • X-ray spectromicroscopy studies of graphene based materials. • X-ray spectromicroscopy studies of nanomaterials for different sensor types. [ABSTRACT FROM AUTHOR]

Angle-Resolved Photoemission Spectroscopy (ARPES) is a premier technique for understanding the electronic excitations in conductive, crystalline matter, in which the induced photocurrent is collected and dispersed in energy and angle of emission to reveal the energy- and momentum-dependent single particle spectral function A (k , ω). So far, ARPES in a magnetic field has been precluded due to the need to preserve the electron paths between the sample and detector. In this paper we report progress towards "magnetoARPES", a variant of ARPES that can be conducted in a magnetic field. It is achieved by applying a microscopic probe beam (≲ 10 μ m) to a thinned sample mounted upon a special sample holder that generates magnetic field confined to a thin layer near the sample surface. In this geometry we could produce ARPES in magnetic fields up to around ±100 mT. The magnetic fields can be varied from purely in-plane to nearly purely out-of-plane, by scanning the probe beam across different parts of the device. We present experimental and simulated data for graphene to explore the aberrations induced by the magnetic field. These results demonstrate the viability of the magnetoARPES technique for exploring symmetry breaking effects in weak magnetic fields. • Angle-Resolved Photoelectron Spectroscopy may be conducted in a magnetic field. • Studies under concentrated magnetic fields are enabled by using micron-scale probes. • Ray-tracing simulations give important guidance on the interpretation of the data. • The data may be used in the magnetometry of microscopic magnetic field distributions. [ABSTRACT FROM AUTHOR]

The beamline, BL4U, in UVSOR-III Synchrotron is dedicated to scanning transmission X-ray microscopy (STXM) based on 2-dimensional soft X-ray absorption and has been in operation since 2013, to enable both academic and industrial users to carry out advanced chemical analysis under various sample environments. In this paper, we have summarized our major developments for the last decade; especially, expansion of the photon energy range down to the Li K-edge (55 eV), sample cryo-cooling to reduce radiation damage, 3-dimensional computer tomography, and air-free sample transfer. • Lithium K absorption edge around 55 eV is available for STXM by reducing higher order harmonics. • Cryo-cooling setup is developed to reduce X-ray radiation damage to samples. • By using computer tomography, 3-dimensional X-ray absorption spectroscopy of an isolated cell nucleus was performed. • Air-free sample transfer system is developed for samples which are highly reactive with oxygen or water. [ABSTRACT FROM AUTHOR]

We review the main developments and first commissioning experiments at the CARNAÚBA X-ray nanoprobe beamline, recently installed at the brand-new Sirius 4th-generation synchrotron radiation source at the Brazilian Synchrotron Light Laboratory (LNLS). The paper briefly discusses the X-ray nanoprobe instrument, emphasizing the first deployed experimental station TARUMÃ, and showcases preliminary results in a broad range of areas that benefit from diverse sample environments. Research domains like photovoltaics, photonics, electrocatalysis, geoscience, and agriculture are investigated from the viewpoint of chemistry, atomic structure, morphology, and redox dynamics phenomena covered by the beamline techniques. Finally, future capabilities are presented based on a new instrument under development. • The CARNAUBA X-ray nanoprobe beamline has been commissioned and it is open to the scientific community. • The first deployed station, named TARUMÃ, has been commissioned and reached design parameters. • The beamline has delivered preliminary science outcomes. [ABSTRACT FROM AUTHOR]

In this paper, using first-principles calculations based on density-functional theory, the electronic structures, magnetic properties, and half-metallicity in the bulk and (001) surface of quaternary Heusler alloy CoNbMnSi are studied. For the bulk, the CoNbMnSi compound shows half-metallicity with a band gap of 0.5 eV in the down-spin direction at a equilibrium lattice constant of 5.88 Ǻ. At a similar equilibrium lattice constant, the half-metallicity confirmed in the bulk CoNbMnSi, is ruined at both NbSi- and MnCo-terminated (001) surfaces and subsurfaces. Based on the magnetic property calculations, the magnetic moments of Mn and Nb atoms at the (001) surfaces increase with respect to the corresponding bulk values, while the magnetic moment of Co and Si atoms decreases. The spin-polarization ratio clearly decreases below 75% for (001) surfaces and subsurfaces of the CoNbMnSi alloy. [ABSTRACT FROM AUTHOR]

The commissioning of the MAX IV synchrotron radiation facility in Lund marks the dawn of a new generation of storage-ring-based light sources. This new generation delivers one order of magnitude higher performance and allows realization of groundbreaking experiments on a variety of systems and materials at the atomic and molecular levels. This paper reviews the conceptual basis of the MAX IV design, briefly summarizes the most recent accelerator commissioning results and focusses on exploring a future development path for the MAX IV 3 GeV storage ring aimed at achieving the diffraction limit at hard x-ray wavelengths. [ABSTRACT FROM AUTHOR]

The complementary capabilities of the Scanning PhotoElectron Microscopes (SPEM) and X-ray PhotoEmission Electron Microscopes (XPEEM), operated at Elettra, in terms of imaging and micro-spectroscopy have opened unique opportunities to explore properties of functional materials as a function of their morphology and dimensions and to follow modifications in their properties during their operation. This paper describes the present performance of SPEMs and XPEEMs at Elettra, illustrated by selected recent studies relevant to graphene science. Ongoing efforts for implementing SPEM set-ups allowing for in-situ investigations under realistic operating conditions and PEEM set-up for spin-filtered momentum microscopy are outlined and discussed as well. [ABSTRACT FROM AUTHOR]

The development of spintronics, the field of science that examines the behavior of systems, based not only on charge transfer, but on magnetic properties of nano-objects as well, requires studying various magnetic and electrical properties of nanoscale systems. To create a new device, it is often important to know a length of spin relaxation not only for electrons with energies close to the Fermi surface, but also with energies of several hundred eV. In this paper we compare results from the spin relaxation length measurements in Pd and LiF. To measure spin-relaxation length for electrons within energy range 35–550 eV spin-polarized secondary electron spectroscopy was used. Experimental results allow us to estimate the influence of the electron–electron and spin-orbit interactions in the processes of electron polarization loss. Values of spin relaxation lengths were measured at room temperature and lie in the range from 18 to 27 Å for Pd and from 70 to 230 Å for LiF. [ABSTRACT FROM AUTHOR]

Various important processes take place at solid/liquid interfaces. Understanding of structural changes accompanying with those interfacial processes is important not only for fundamental science but also for a wide range of applications, especially electrocatalysis. In the last several decades, a variety of microscopic and spectroscopic techniques have been developed to observe geometric/molecular/electronic structures at the solid/liquid interfaces in situ. However, techniques to probe the electronic structure of electrocatalysts are still limited because of the complexity of the experimental setup and the interpretation of results. Since the 1980s, our groups have developed and utilized various techniques which enable to investigate those structural changes under electrochemical potential control. In the present paper, our recent research progress on the electronic structure at solid/liquid interfaces, (1) in situ XAFS studies on molecular catalysts confined within molecular layers and electrocatalysts for oxygen reduction reaction in polymer electrolyte membrane fuel cells, (2) development of an in situ electrochemical XPS apparatus for the solid/liquid interfaces and (3) investigation of the electronic structure of metal surfaces modulated by adsorbed species by in situ DR-SFG is briefly reviewed. [ABSTRACT FROM AUTHOR]

Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212) superconducting whiskers, owing to their microscopic size, are good candidates for the fabrication of miniaturized devices for production/sensing of THz-radiation based on their Intrinsic Josephson Junctions (IJJ) properties. With this respect, several studies demonstrated the possibility of controlling whisker IJJ parameters by modifying the oxygen content. In this paper we show that both thermal annealing and hard X-ray irradiation are effective ways to tune the oxygen doping. In particular, we monitored the effect of an annealing process at 363 K and of irradiation by 17 keV micro- and nano-beams on the structural and superconducting properties of selected Bi-2212 whiskers. Moreover we modeled by a finite element simulation the temperature field induced by the X-ray beam to try to clarify the origin of the measured changes. [ABSTRACT FROM AUTHOR]

Crucial for the advancement of electrochemical materials science is understanding the lateral variations in the elemental and chemical state of constituents induced by electrochemical reactions at nanoscales. This requires in situ studies to provide observables that contribute to both modeling beyond the phenomenological level and transducing exactly the functionally relevant quantities A range of X-ray coherent diffraction imaging (CDI) approaches has recently been proposed for imaging beyond the diffraction limit with potentially dramatic improvements of time resolution with chemical sensitivity. In this paper we report a selection of ptychography results obtained in situ after successive steps of electrochemically driven growth, complemented with absorption and phase spectroscopy at high lateral resolution. We demonstrate the onset of morphological instability feature formation and correlate the chemical state of Mn with local growth rate controlled by the current density distribution resulting from morphological evolution. [ABSTRACT FROM AUTHOR]

In this paper, we show that the energy resolution of a classical one-step cylindrical mirror analyzer can be made three times better by adjusting its geometrical parameters. • We have optimized a one-step cylindrical mirror analyzer. • For an entrance solid angle of 0.59 steradians, the optimized base resolution is 0.1% • It is three times better than resolutions of known one-step analyzers. [ABSTRACT FROM AUTHOR]

The typical output of a STXM (Scanning Transmission X-ray (spectro)Microscopy) measurement is a data cube consisting of a set of images (measurements of X-ray transmission at a grid of pixels) taken at a sequence of incident energies. As with any experimental measurement, this raw data must be reduced to some standard form and interpreted. In this paper, I review the basics of how to go from raw data to information about the sample. I will discuss the fundamentals of X-ray spectromicroscopy, data reduction, descriptive and model-based analysis, and available software, with examples taken from the literature. • STXM measurements produce a datacube consisting of XANES spectra at each pixel. • The job of extracting meaning from STXM data can be split into data reduction (to a standardized form) and data analysis. • This review describes basic steps for analysis, with reference to the literature and an example dataset. • Available software is described [ABSTRACT FROM AUTHOR]

Spectral measurements provide valuable information on the electronic states and crystal structures of materials. In particular, X-ray photoelectron spectroscopy (XPS) can facilitate the analysis of the chemical-bond states of the surfaces of materials. In the analysis of XPS spectra, the spectrum to be measured is typically compared to a reference spectrum measured from a known single-phase sample. Therefore, establishing a reference spectral database is imperative. In this study, round-robin tests (RRT) of XPS spectra are performed to obtain recommended XPS reference spectra and develop appropriate measurement conditions, including preprocessing procedures. Determining the variations in peak structures between equipment- and sample-derived spectral shapes and quantitatively discussing them through RRT of XPS spectra are challenging. Therefore, an analysis method that automatically determines the above-mentioned variations and extracts the sample-derived common spectral structures is developed in this study. This paper presents a new approach to the quantitative analysis of round-robin XPS spectral tests. The required common peak structure, a new definition of the XPS reference spectrum, is obtained. Further, a correlation between the variability of deviations in the spectral data of the RRT and the measurement condition and XPS measurement equipment used is determined. Such a framework is essential for standardizing XPS spectra and expanding the XPS reference spectral database. • A novel quantitative analysis method was established for round-robin tests (RRT) of spectral measurements. • This method visualizes slight changes in spectral fine structure caused by measurement conditions with respect to the common peak structure, and provides candidate factors for such changes. • Multiple spectral data were integrally analyzed to reproducibly provide correlations between spectral fine structures and measurement conditions. • An XPS reference database expansion and standardization framework were developed. [ABSTRACT FROM AUTHOR]

The interaction of alkali ions with multilayer graphene is critical in many applications, for example in energy storage devices. This requires a detailed understanding of ion interactions with carbonaceous layers. The mechanism of ion intercalation into graphene can be different from that observed for hard graphite. In this paper, we present an investigation of the vertical alkali ion (Na, K, Cs) distribution on multilayer graphene deposited onto SiO 2 in vacuum and in the presence of water vapor using Standing Wave Ambient Pressure Photoemission Spectroscopy. It was found that Cs, K, and Na ions do not intercalate into multilayer graphene under vacuum conditions. The most likely reasons for this behavior are the reversibility of the process due to large inter-sheet spacing or lack of time for intercalation. When exposed to water vapor, Na ions intercalate soft carbon whereas Cs ions do not. This is a clear indication for the difference in the intercalation mechanisms on hard graphite and soft graphene. • Interaction of alkali metal ions with multilayer graphene on SiO 2 have been studied in vacuum and in the presence of water vapor. • Standing Wave Ambient Pressure Photoemission Spectroscopy was used to obtain vertical profiles for Na, K, and Cs ions deposited on the supported graphene and how it is changing in the presence of water. • Under vacuum alkali metal ions do not intercalate supported multilayer graphene. • Unlike on hard graphite, on soft multilayer graphene upon exposure to water Na ions intercalate graphene sheets whereas Cs ions do not. • Difference between behavior of Na and Cs in the presence of water on graphite and multilayer graphene seem to arise from more relaxed spacing and presence of pores. [ABSTRACT FROM AUTHOR]

This paper reports the X-ray photoelectron spectroscopy (XPS) and X-ray excited Auger electron spectroscopy (XAES) measurements on Fe 1− x Ni x ( x = 0.4, 0.5, 0.6, 0.7, 0.9) alloys prepared by arc melting method. Valence band spectrum of Fe 0.6 Ni 0.4 alloy exhibits a shift of about 0.15 eV to higher binding energy at 10 K compared to that at 300 K suggesting the precipitation of antiferromagnetic phase below 20 K. Ni L 3 M 45 M 45 Auger spectra exhibit composition induced changes. The Ni L 3 M 45 M 45 Auger spectrum of Fe 0.6 Ni 0.4 alloy exhibits an anomalous increase of intensity in the kinetic energy range from 841 to 845.8 eV at 10 K compared to that of 300 K. Such an increase in intensity of the Auger signal also supports the precipitation of new fcc antiferromagnetic phase below 20 K. Fe L 3 M 45 M 45 Auger overlaps with Ni L 3 M 23 M 23 Auger transition and thus becomes complicated to analyze and obtain temperature or composition induced changes. [ABSTRACT FROM AUTHOR]

We present here theoretical investigations of electronic states and electron scattering cross-sections of the thiazole molecule. Spectroscopic calculations are performed on ground and excited states of thiazole using density functional theory (DFT) and time dependent DFT, while the electron impact scattering calculations are carried out using ab initio R-Matrix method. The optimized geometrical parameters and computed vibrational frequencies of neutral and cationic thiazole molecule are in good agreement with earlier work. Detailed comparison of the present computed vertical excitation energies with earlier experimental studies helps to confirm several of the earlier assigned Rydberg transitions while leading to revised assignments for some of the earlier observed peaks. Extensive electron scattering cross-sectional data; Elastic cross-sections include symmetry decomposition, differential and momentum transfer cross-sections while inelastic cross-sectional data comprises of discrete electronic excitations and ionization cross-sections along with their rate-coefficients. According to literature survey, this is the first report of cross-section data and rate coefficients for inelastic processes. A comparison of the total cross-sectional (TCS) data of thiazole with the TCS data of the isoelectronic thiophene molecule reveals the overall TCS values being higher in thiazole, as expected due to its higher dipole moment. Further, resonant peaks in the TCS are observed to be shifted to lower energies in thiazole as compared to thiophene, which is attributed to the higher electronegativity of the N atom as compared to the CH group in thiophene. For the first time, a comprehensive spectroscopic and electron scattering study of thiazole is summarized in this paper. • Comprehensive spectroscopy and electron scattering study on thiazole. • The geometrical parameters and IR frequencies agree well with earlier work. • Comparison with earlier data; confirm/revised assignments of Rydberg states. • Low energy electron scattering data for Thiazole from 0.1 eV to 20 eV. • This data help to understand various electron induced biochemical processes. [ABSTRACT FROM AUTHOR]

Antiferromagnetic (AFM) materials were not well respected from practical point of view until the discovery of interlayer exchange coupling in 1986 and giant magnetoresistance (GMR) in 1988–1989. Soon after, the old discovery (namely exchange anisotropy in 1956) and surface antiferromagnetism find their practical importance in magnetic recording, storage and sensor devices. However, the progress is partly hindered by limited experimental techniques to study surface AFM properties. This paper reviews recent experimental advances in the field of surface antiferromagnetism of prototype AFM oxide NiO(100), particularly using laterally resolved magnetic spectroscopy. Studies performed on bare NiO(100) single crystal and thin films using photoemission electron microscopy (PEEM) with X-ray magnetic linear dichroism (XMLD) as contrast mechanism and using a recently proposed approach utilizing the capability of a low energy electron microscope (LEEM), namely AFM-LEEM, are highlighted. We expect that AFM-LEEM in combination with XMLD-PEEM will soon explore more finer aspects AFM materials. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis of trivalent Tb 3+ doped Sr 3 B 2 O 6 phosphor by combustion method using urea as an organic fuel. The structure of the product has been verified by X-ray diffraction study which shows a rhombohedral phase with a space group of R-3c having lattice constants a = 9 .064 Å, b = 9.064 Å, c = 12.611 Å. X-ray photoelectron spectroscopy has been used to study the elemental composition and electronic states of the Tb 3+ doped Sr 3 B 2 O 6 phosphor. Photoluminescence spectra showed that the phosphor emits in the greenish region (with the main peak at 544 nm) of color gamut under UV excitation. The diffuse reflectance spectra of the Sr 3 B 2 O 6 phosphor were studied. Lifetime and band gap of the phosphors were calculated to be 2.55 ms and 5.25 ± 0.02 eV, respectively. [ABSTRACT FROM AUTHOR]

With the recent availability of a high order FDM solution to the curved boundary value problem, it is now possible to determine potentials in such geometries with considerably greater accuracy than had been available with the FDM method. In order for the algorithms used in the accurate potential calculations to be useful in ray tracing, an integration of those algorithms needs to be placed into the ray trace process itself. The object of this paper is to incorporate these algorithms into a solution of the equations of motion of the ray and, having done this, to demonstrate its efficacy. The algorithm incorporation has been accomplished by using power series techniques and the solution constructed has been tested by tracing the medial ray through concentric sphere geometries. The testing has indicated that precisions of ray calculations of 10 −20 are now possible. This solution offers a considerable extension to the ray tracing accuracy over the current state of art. [ABSTRACT FROM AUTHOR]

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 of 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 complementarity 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 our further understanding of chemical analysis. [ABSTRACT FROM AUTHOR]