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.