Journal of Electron Spectroscopy and Related Phenomena最新文献

The synchrotron x-ray spectromicroscopy technique Scanning Transmission X-ray Microscopy (STXM) offers a powerful means to examine the underlying biochemistry of biological systems, owing to its combined chemical sensitivity and nanoscale spatial resolution. Here we introduce and demonstrate methodology for the use of STXM to examine the biochemistry of the human brain. We then discuss how this approach can help us better understand the biochemical changes that occur during the development of degenerative brain disorders, potentially facilitating the development of new therapies for disease diagnosis and treatment.

Soft X-ray spectro-ptychography of nickel-nitrogen-carbon electrocatalysts containing atomically dispersed Ni-based active sites were measured at the Ni L₃ edge. Samples prepared with two different loadings of Ni precursors were investigated and compared to the results of an earlier study using scanning transmission X-ray microscopy (STXM) [Zhang et al., ACS Catalysis 12 (2022) 8746]. The ptychography data sets were measured using a defocused probe (1–3 µm). The spatial resolution was improved from ∼60 nm (STXM) to ∼20 nm (ptychography). Spectro-ptychography stacks were measured at 4 component-specific energies (4-E stack) and at many energies across the full Ni L₃ edge (34-E stack). Maps of three key chemical components (Ni metal, Ni₃S_2, and atomically dispersed N-coordinated Ni catalyst sites) were derived by fits of suitable reference spectra to absorption signals derived from the amplitude images from ptychographic reconstruction. The spectro-ptychography 4-E and 34-E stacks gave chemical mapping similar to each other and to the earlier STXM results. The phase signals obtained from the same data set and reconstruction were also found to be analyzable using reference phase spectra extracted from the phase stack, which generated chemical maps similar to those based on ptychography amplitude data. By using a defocused probe, the radiation dose and acquisition times for spectro-ptychography are comparable to conventional STXM, but significantly improved spatial resolution was achieved. This study highlights the added value of spectro-ptychography relative to STXM for studies of electrocatalysts.

Calcium minerals are ubiquitous in geology and life chemistry. Understanding the phase and chemical state of calcium minerals is important for numerous processes including materials chemistry, hard tissue biogenesis and geological processes. Photoemission spectroscopies such as near edge X-ray absorption fine structure (NEXAFS) and scanning transmission X-ray microscopy have been instrumental in identifying and characterizing calcium minerals in all these areas. In this work, we have recorded reference spectra for a range of different calcium minerals including a series of calcium carbonates, calcium oxalates and calcium phosphates. While collections of reference spectra for several calcium minerals can be found in the literature, these spectra have been reported in different contexts using a variety of instruments. We, here, report a comprehensive list of references recorded in parallel in a single experiment by imaging an array of calcium minerals using a NEXAFS microscope. We present reference NEXAFS spectra at the calcium L-, carbon K- and oxygen K-edges.

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.

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.

Metal-halide perovskites are complex materials with outstanding optoelectronic properties. Thus it is of interest to analyze these materials by using every available research tool. Synchrotron tools have played an important role in fundamental and applied research for decades. Many synchrotron-based hard X-ray tools are already providing effective feedback to the perovskite solar cell (PSC) research community. With several fourth-generation light sources up and running or under development, this contribution will continue to impact every aspect of scientific advancement including PSC research. Arguably, the contribution of soft X-rays in PSC research is relatively limited. In view of the developments in the synchrotron world and the fact that a multimethod approach, combining laboratory-based techniques as well as synchrotron-based techniques, is necessary to provide constructive feedback to the PSC community we present here a collection of arguments and procedures with the aim of highlighting the use of soft X-ray scanning transmission X-ray microscopy (STXM). Some aspects of these arguments are elaborated with STXM investigation of perovskite material formamidinium-methylammonium lead iodide (FA_1−xMA_xPbI₃).

Selective and label-free probing of drugs by scanning transmission X-ray microscopy (STXM) is applied along with hyperspectral imaging to probe topically applied drugs in human skin explants ex vivo. A comparison of data evaluation strategies is reported, which includes changes in optical density at selected photon energies in the O 1 s regime, linear combination modeling using reference spectra, as well as principal component and cluster analyses. It is shown that consistent results are obtained from linear combination modeling of reference spectra and changes in optical density. The dermal penetration of the anti-inflammatory drug rapamycin is investigated with high spatial resolution using a petrolatum-based formulation. For such well-known formulation the result of occlusion is investigated leading to drug uptake into corneocytes. Additional changes in drug penetration induced by weakening the skin barrier by the serine protease trypsin are also included. These results are discussed in comparison with the dermal penetration of other drug formulations. Finally, alternatives to present data acquisition strategies in STXM are discussed with respect to sub-sampling in combination with mathematical approaches, so that the full chemical and spatial information can be retrieved and radiation damage is minimized.

We report on the experimental investigation of single crystals of trans-[RuNOPy₄F](ClO₄)₂ (1) in its ground state (GS). The X-ray absorption spectroscopy (XAS) spectra measured at the N, O and F K-edges were compared to TDDFT calculations to identify and assign the absorption peaks, and to elucidate the structures of coordinated nitric oxide (NO). Based on a reasonable match of experimental and calculated spectra of GS, the N, O and F K-edges XAS spectra of Ru-ON (MS1) and Ru-η²-(NO) (MS2) isomers of 1 were calculated. According to the calculations, the energy or/and intensity of the 1 s→LUMO, LUMO+ 1 peaks of N, O or F K-edge changes significantly after GS isomerization to both MS1 and MS2. Current theoretical modeling of the NO linkage isomer in 1 is a background for the future investigation of isomerization process of NO by XAS methods. Since the investigated isomerization occurs in a variety of different nitrosyl complexes, obtained results can be extrapolated to a large family of transition metal nitrosyl compounds.

Spectromicroscopy refers to analytical methods that combine imaging and spectroscopy to provide detailed, spatially resolved analytical information about a sample, such as the type and quantitative spatial distributions of chemical components, geometric or magnetic alignment information, crystal structure, etc. The analysis of X-ray images and spectra (aXis2000) software described in this work provides a set of routines within a single, integrated, graphical-oriented package to read, display, manipulate and analyze spectromicroscopy data, with particular focus on soft X-ray spectromicroscopy methods such as scanning transmission X-ray microscopy (STXM), X-ray photoemission electron microscopy (XPEEM), scanning photoelectron X-ray microscopy (SPEM) and transmission X-ray microscopy (TXM). Here, this free software is described and compared to other software that can provide similar or complementary capabilities. Examples of spectromicroscopic analyses using advanced features of aXis2000 are provided.

A theoretical study of integral and differential cross sections as well as of spin-polarization effects is reported for elastic electron scattering by zinc atoms at collision energies up to 3 keV. It has been shown that a P-wave shape resonance appears in the low-energy range of the integral cross sections. Its energy is about 0.19 and 0.20 eV, while its width is about 0.309 and 0.356 eV for the j = 3/2 and j = 1/2 total angular momentum of the electron, respectively. The differential cross sections of scattering and the Sherman-functions $S(E,\theta )$ are computed by the parameter-free complex optical potential method. The calculated data are in a good overall agreement with the available experimental and theoretical data in the literature. The energy and angular positions have been located for five critical minima in the differential cross sections. The low-energy minimum is located at [6.63 eV; 102.34°], while the high-energy minimum is at [347.53 eV; 124.11°]. Ten points for the scattered electrons' total spin-polarization ($S=\pm 1$) have been found in the vicinity of the critical minima along with the energy and the angular widths of the spin-polarization peaks (where $\left|S\right|\ge 0.9$).