Journal of Electron Spectroscopy and Related Phenomena最新文献

This work focuses on the EXAFS investigation of the local environment of lead and iron sorbed onto volcanic ash materials previously studied using XANES technique. Different compounds found in the composition of volcanic ash were used as the models in the EXAFS fitting procedure of the experimental EXAFS spectra collected at the Fe K edge and Pb L3 edge in the Fe- and Pb-sorbed volcanic ash samples. The results showed two types of interactions involving in the adsorption process of both samples. The first is related to iron or lead absorber with oxygen atoms in the first coordination shell. The second interaction occurred between the absorbers (Fe or Pb) and the backscatters (Fe or Pb) in the second shell. The local environment of the iron-sorbed element may have a cubic geometry with different crystallographic sites related to oxygen and iron atoms. On the other hand, the lead-sorbed element may be in orthorhombic geometry with different sites related to oxygen atoms and lead atoms. The adsorption mechanisms involved in the process of iron and lead sorption are ion exchange with probable chemisorption for iron and microprecipitation for lead.

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.

The F, C, O, and N elemental distribution maps at the exfoliated surfaces of Cu plate after peeling the fluoropolymers from Fluorinated ethylene propylene (FEP)/Cu and Perfluoroalkoxyalkane (PFA)/Cu pieces which were bonded by plasma treatment including amino acid were performed by microscopic synchrotron radiation (SR)　spectroscopic imaging measurements. The spatial elemental distribution pattern of exfoliated Cu after peeling PFA/Cu piece was not detectable by scanning electron microscopy with energy dispersive X-ray spectroscopy imaging alone, was revealed by SR-based soft X-ray microspectroscopy. We also obtained the microprobe X-ray fluorescence spectra and microprobe near-edge X-ray absorption fine structure spectra. Based on these measurement results, it is considered that the delamination of FEP/Cu piece mainly caused by resin failure, while the delamination of PFA/Cu is caused by interfacial delamination in addition to resin failure. The Hard X-ray photoelectron spectroscopy was also performed to confirm that the bonding via nitrogen is formed. Our SR-based analyses provided confirmation that fluoropolymers and Cu plates are bonded by N-mediated chemical bonding. The present study insists that the technique and plasma bonding process reported are expected to contribute to the development of new devices and systems consisting of fluoropolymers and metals.

The radiation damage issue consequent to soft X-rays’ exposure is still an important aspect to be contemplated in soft X-ray microscopy. The work presented here is part of a more extended investigation on the topic and targets the effects of soft X-rays exposure on plant tissues.

The aftermaths of soft X-rays’ exposure were evaluated by FTIR spectromicroscopy by comparing irradiated and non-irradiated areas on similar plant structural features, one day and ten days after irradiation, to highlight also a possible time-dependent behavior consequent to air exposure.

Our results show partial degradation of lignocellulosic complex and oxidation of cellulose and most probably of hemicellulose; lignin moiety of cell walls in vascular tissue however remains stable.

Comparing the current study with our previous works it appears that, as expected, plant tissues seem less prone to soft X-rays radiation damage compared to mammalian cells or tissues.

Calcium plays an important role in the physiology of bacterial cells and as a free soluble form inside the cells, it is tightly regulated at a low concentration. However, much higher amounts of stored calcium exist within cells and can be remobilized at diverse occasions. As a consequence, there has been a variety of techniques developed to quantitatively map the different forms of Ca in cells. Here we show how scanning transmission x-ray microscopy (STXM), a synchrotron-based microscopy technique, conducted in the soft x-ray range at the Ca L_2,3 edges (340–360 eV) offers an original and informative quantitative view of different Ca reservoirs in bacterial cells at a spatial resolution better than 100 nm. To illustrate this, we analyzed mutants of the cyanobacterium Synechococcus elongatus PCC 7942, overexpressing different versions of a gene called ccyA from two phylogenetically distant cyanobacteria: Gloeomargarita lithophora and Synechococcus sp. PCC 6312. This gene is diagnostic of the capability of some cyanobacteria to form intracellular amorphous calcium carbonate (iACC) but its function remains unknown. Here we show that the overexpression of the ccyA gene in the iACC non-forming cyanobacterium S. elongatus PCC 7942 results in an increased Ca content, especially in some Ca-rich cells. Moreover, we show that STXM can discriminate four different reservoirs of Ca in cyanobacteria and provides quantitative assessment of their relative importance.

Dissociative electron attachment (DEA) to 1-chloroanthracene and 9-chloroanthracene was investigated under gas-phase conditions. In both compounds, the elimination of the chlorine anion is the dominant channel for the dissociation of molecular negative ions (NIs). The second most intense channel leads to the formation of molecular anions (Mˉ). The autodetachment lifetime of Mˉ was measured to be about 170 μs for both compounds. The widths of the Mˉ peaks indicate that molecular anions are formed via two resonances: at thermal electron energies and through a shape resonance at the energy of ∼0.5 eV. Adiabatic electron affinities were estimated in the framework of the simple Arrhenius model to be 0.86 eV for both molecules, the values being close to the theoretical predictions by DFT method of 0.90 eV and 0.93 eV for 1-chloroanthracene and 9-chloroanthracene respectively. Metastable negative ions are observed in the DEA spectra of both molecules, which testifies that the elimination of chlorine anions from molecular NIs appears on a time scale of several microseconds.

Chitosan–acrylic acid (Cs–AA) hydrogels were prepared by blending different Cs concentrations and AA:Cs ratios. The Cs–AA hydrogel samples were analyzed using synchrotron radiation-induced near edge X-ray absorption fine structure (NEXAFS) and Fourier transform infrared (FTIR) spectroscopies. The characteristics of Cs were observed through the C, O, and N K edges in NEXAFS. Significant shifts in the Cs characteristic features were induced by the addition of AA. The NEXAFS findings confirmed the new covalent and ionic bridges to form the network of the Cs–AA hydrogel. Raw FTIR spectra were used to investigate the different functional groups of each of the macromolecules. The study attempted to discriminate the Cs–AA hydrogels prepared with different Cs wt% concentration and AA:Cs ratio using multivariate approaches. The preprocessed dataset was evaluated using principal component analysis (PCA) and hierarchical cluster analysis (HCA). The PCA and HCA methods showed the possibility of discriminating the Cs–AA hydrogel samples from the control samples and with each other. The approaches further confirmed that the CO groups found in the range of 1700–1800 cm⁻¹ can be used as an identifier for Cs–AA hydrogel samples prepared using different solution parameters. The use of FTIR coupled with multivariate approaches provided a simple and reliable way to inspect the possible discrimination of Cs–AA hydrogels.

Over 50 years of development, synchrotron based X-ray microscopy has become a routine and powerful tool for the analysis of nanoscale structure and chemistry in many areas of science. Scanning X-ray microscopy is particularly well suited to the study of chemical and magnetic states of matter and has become available at most synchrotron light sources using a variety of optical schemes, detectors and sample environments. The Advanced Light Source at Lawrence Berkeley National Laboratory has an extensive program of soft X-ray scanning microscopy which supports a broad range of scientific research using a suite of advanced tools for high spatio-temporal resolution and control of active materials. Instruments operating within an energy range between 200–2500 eV with spatial resolution down to 7 nm and sub 20 picosecond time resolution are available. These capabilities can be routinely used in combination with a variety of sample stimuli, including gas or fluid flow, temperature control from 100 to 1200 K, DC bias and pulsed or continuous microwave excitation. We present here a complete survey of our instruments, their most advanced capabilities and a perspective on how they complement each other to solve complex problems in energy, materials and environmental science.

Energetic (multiple keV) electrons scattering at high momentum transfer (i.e. scatter over a large angle ($>20$°)) interact with a single particle, either a nucleus or a target electron. Energy transfer is then determined by the incoming energy, scattering angle and the mass and velocity of the scattering particle. When scattering from a target electron a large fraction of the incoming energy is transferred and scattered and ejected electrons can be detected in coincidence. The experiment is then known as electron momentum spectroscopy or (e,2e) spectroscopy and information about the electronic structure is obtained. When scattering from a nucleus the transferred energy is much smaller, and only the scattered electron can be detected. Then the experiment is known as electron Rutherford backscattering and one can measure the sample composition and vibrational properties. In this review we give examples of experimental results for both cases to illustrate the unique information that can be obtained by electron spectroscopy at high-momentum transfer, a less-frequently utilised experimental condition.