Journal of Electron Spectroscopy and Related Phenomena最新文献

A detailed spectroscopic simulation of the original Pu N_4,5 and O_4,5 X-Ray Absorption Spectroscopy (XAS) has been performed. Additionally, a fundamental flaw in the Electron Energy Loss Spectroscopy (EELS) measurement has been corrected. Thus, the determination of the 5f occupation (n) in elemental Pu has been re-evaluated with the result that n = 5.0 ± 0.1 for αPu and n = 4.9 ± 0.2 for δPu. These values are significantly lower than the value of ∼5½ that was propagated earlier.

The question of the intensity-energy response of photoemission spectrometers has been approached through a round-robin involving 13 instruments working with low (Al/Mg-K$\alpha$) and high (Cr-K$\alpha$) energy photon sources. An algorithm based on the analysis of inelastic background previously proposed [S. Guilet et al., J. Electron Spectrosc. Relat. Phenom. 285 (2022) 147225)] was intensively tested against calibrated Al/Mg-K$\alpha$ instruments and calculated relative sensitivity factors (RSFs) over the 15 core level peaks of coinage metals (Ag, Au, Cu). In both cases, the linear correlation within $\pm 10$ %, over two orders of magnitude in intensity and for kinetic energies ranging from $\sim 400$ to $1400\mathrm{eV}$, showed the consistency of the approach. All the contributions to RSFs (e.g. non-dipolar terms in the photo-ionization cross section, elastic scattering effects, surface excitations, beam polarization by the monochromator) were critically reviewed and taken into account using the state-of-the-art modellings and databases. Strong variations were evidenced among instruments, regarding not only the response functions, but also the theoretical RSFs due to different measurement geometries. For the Cr-K$\alpha$ hard x-ray instruments, the same analysis was performed with a set of different materials (Al, Si, Ge, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ag, W, Au). A $\pm 10$ % satisfactory agreement against theoretical RSFs over 69 core levels spanning a large kinetic energy range (300–4000 eV) could be achieved with a common response function. Despite limitations that are reviewed, this work opens interesting perspectives for a systematic calibration of photoemission instruments.

A semiempirical approach to describe low energy electron–atom transport cross sections of easy implementation and reproduction is presented. The heart of the model is an energy independent two-parameter potential that was adjusted to reproduce the accurate total cross sections for He, Ne, Ar and Kr, measured with a threshold photoelectron source technique from meV up to 20 eV. Once the potential was conceived, the model was validated by comparing the values obtained for the calculated scattering lengths and phase shifts with the respective quantities previously reported in the literature. We close the article by presenting the momentum transfer and viscosity cross sections. Good agreement is found when compared to the similar data obtained from swarm experiments, from phase shifts according to differential cross section measurements and to the cross sections reported by sophisticated ab initio relativistic many-body calculations. Tables for the phase shifts and cross sections are provided for direct use and applications.

β-SiC nanoparticles are one of the most common reinforcements in Mg-Al alloy matrix nanocomposites (MgMNCs). The interfacial interactions between β-SiC and the alloy matrix are complex due to the occurrence of new phases and the fine scale of the 3D architecture. This study aims to explore the feasibility of using synchrotron Scanning Transmission X-ray spectro-Microscopy (STXM) to investigate such interfacial interactions and acquire reference X-ray Absorption Spectroscopy (XAS) data for some common interphase crystals present within the composites, which are not readily available. Throughout this study, a reliable procedure for collecting STXM data on samples derived from MgMNCs was developed, and reference XAS spectra for α-Mg, β-Mg₁₇Al₁₂, T2-Al₂MgC₂, Mg₂Si and MgO present in MgMNCs were collected. The accessibility of STXM and spatially resolved XAS spectrum is not only useful for nanocomposite alloy research but applicable widely across the magnesium alloy research community when identifying and quantifying the phases with complex crystal structures and oxide states.

The vertical, valence ionization energies for three peroxide based explosives: triacetone triperoxide (TATP), hexamethylene triperoxide diamine (HMTD) and diacetone diperoxide (DADP) have been calculated (as free molecules) using high-level ab initio coupled-cluster method: IP-EOM-CCSD. The calculated vertical, valence ionization energies were used to simulate UV photoelectron spectra. Our results, especially 1st ionization energies are discussed together compared with previous results on adiabatic energies. The variations of vertical ionization energies were rationalized by the analysis of the electronic structure of PBEs. The valence electronic structures depend on the number, type and position of peroxide groups. HOMO-LUMO gaps and the influence of electronic structures on explosive properties were also discussed.

A package based on the Igor Pro scripting language is proposed for the analysis of photoemission spectroscopy data (XPS, HAXPES, UPS). Compared to the already numerous available softwares, the Igor Pro Paris Photoemission Package (I4P) gathers in a single tool: (i) basic data analysis and plotting features (such as satellite/ghost line deconvolution, inelastic background subtraction, determination of the intensity-energy response function and its correction, peak overlap, energy-mass conversion in ion scattering spectroscopy), (ii) databases of binding energies, of photo-ionization cross sections, of inelastic/transport mean free paths and effective attenuation lengths, (iii) quantification based on elastic peak areas accounting for elastic scattering, (iv) depth profiling by angle-resolved photoemission and by inelastic background analysis, (iv) peak fitting with 17 different line shapes including background and fully configurable constraints between fit parameters. Aside a detailed manual including the references to the relevant literature, I4P comes not only with a graphical interface but also with scripting commands. Most of all, the free availability of the source code allows the potential user to easily develop additional options of data treatment.

State-selective total and angular differential cross sections for positronium formation are presented in the collision of positron with helium atoms in their ground state by using the four-body formalism of the boundary-corrected continuum-intermediate-states approximation. The main purpose of the present study is to investigate the relative importance of intermediate ionization continuum states that has been incorporated with a suitable choice of distorting potential. In addition, the nine-dimensional integrals of the transition amplitude are analytically reduced to a one-dimensional real integral, which can be easily calculated numerically. The influence of the target static electron correlations on the capture probability is investigated using the different bound-state wave functions of He. The theoretical model for the calculation is fairly accurate and predicts a number of interesting features of the state-selective total and differential cross sections in the range of positron impact energy varies from 20 to $250\mathrm{eV}$. The total cross sections are highly peaked at an impact energy of 50 eV. The results are compared with those of other theories and the available experimental data. The present theoretical results and other measurements show satisfactory agreement in the wide energy range. Moreover, surface plots for the state-selective differential cross sections are also presented to illustrate the interesting feature of the positronium formation in this collision process.

The significance of theoretical, experimental, and analytical methods in calculating the intensity ratios of L-shell transitions for diverse elements lies in their widespread applications across various domains, including physical chemistry and medical research. In the present paper, empirical values for intensity ratios were computed through polynomial interpolations using experimental databases within the scope of atomic number 39 ≤ Z ≤ 92 for $\frac{I_{L\beta }}{I_{L\alpha }}$ and $\frac{I_{L\gamma }}{I_{L\alpha }}$, and extending to the range of 39 ≤ Z ≤ 94 for $\frac{I_{\mathrm{Ll}}}{I_{L\alpha }}$. Additionally, new theoretical calculations were conducted using the Multiconfiguration Dirac–Fock Method for specific elements. The obtained results were compared with standard theoretical, experimental, and empirical values, showing a reasonable agreement with them.

The crystal structure of the ternary phosphide Ce₂Ni₁₂P₅ (La₂Ni₁₂P₅-type structure) has been determined from X-ray powder diffraction data: full profile refinement, monoclinic symmetry, space group P2₁/m, a = 10.7809(2) Å, b = 3.6869(1) Å, c = 13.1490(3) Å, β = 107.776(4)º, R_I = 0.068, R_P = 0.044, R_wP = 0.060. Ce₂Ni₁₂P₅ is a ferromagnet with a Curie temperature of 5.8(5) K. A significant deviation from the linearity of the temperature dependence of the electrical resistance for Ce₂Ni₁₂P₅ has been found. The low-temperature part of the electrical resistance indicates the presence of magnetic interactions in Ce₂Ni₁₂P₅. The influence of a magnetic field on the electrical resistance of Ce₂Ni₁₂P₅ has been studied. The X-ray absorption spectrum at the Ce L_III edge and X-ray emission spectra of Ni and P at the K and L_III edges have been studied experimentally and theoretically using DFT+U calculations. The calculations show good agreement with the experimental measurements. The effective valence of Ce in Ce₂Ni₁₂P₅ determined based on the Ce L_III absorption spectrum is ϑ_eff ∼ 3.05.

A method of straightforward construction and analysis of the cascade decay trees is applied to study the cascade energy reemission by silver atoms upon photoionization in the incident photon energy range of 0.01–100 keV. Cascade electrons and photons emitted during the cascade relaxation of an inner-shell vacancy carry away a significant part of the energy initially acquired by the silver atom in a photoionization act. The energies redistributed through following channels were calculated as functions of incident photon energy: energy absorbed by the silver atom itself (a), and energies carried away by the cascade electrons (b) and photons (c). Channel (a) is dominant only at small incident photon energies up to the M₅ ionization threshold. Channel (b) dominates between M and K thresholds making 57–85 % of the acquired energy. Above the K threshold, the weight of channel (b) is still significant, 24 %, however, dominant is channel (c).