Journal of Electron Spectroscopy and Related Phenomena最新文献

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.

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.

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.

We have developed a framework for solving the inverse problem of X-ray photoelectron spectroscopy (XPS) by incorporating an XPS simulator, Simulation of Electron Spectra for Surface Analysis (SESSA), into Bayesian estimation to obtain an overall picture of the distribution of plausible sample structures from the measured XPS data. The Bayesian estimation framework automated the very tedious task of adjusting the sample structure parameters manually in the simulator. As an example, we performed virtual experiments of angle-resolved XPS on a four-layered sample, and we estimated the sample structures based on the XPS intensity data obtained from experiments. We succeeded in not only obtaining an optimal solution, but also visualizing the distribution of the solution through the Bayesian posterior probability distribution.

We developed a soft X-ray microscopic imaging system, CARROT, that combines ptychography and fluorescence X-ray microscopy using a total-reflection Wolter mirror illumination system. The system offers advantages such as achromaticity and long working distances, enabling seamless application to a wide wavelength range. We demonstrated high-resolution imaging of cellular structures and sub-micrometer-scale changes induced by drug administration in mammalian cells. We further showcased the capability to seamlessly switch from ptychography measurements to X-ray fluorescence measurements at different wavelengths to map elemental distributions within cells. Our findings suggest that this system can be used for investigating the correlation between intracellular structures and elemental distribution, as well as for multimodal measurements of visible light fluorescence, Raman scattering, and soft X-rays to provide valuable insights into understanding intracellular dynamics.

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 $A(k,\omega )$. 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 ($\lesssim$10 $\mu m$) 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.

Methylammonium lead iodide CH₃NH₃PbI₃ (MAPI) is one of the hybrid organic–inorganic perovskites (HOIPs) widely considered for photovoltaic devices. Since photoemission is possibly the best technique for the experimental determination of the bands, we have calculated photoemission spectra at the main photon energies available at conventional laboratories (He I - 21.2 eV, He II - 40.8 eV) by performing fully relativistic Spin-Polarized Relativistic Korringa–Kohn–Rostoker (SPRKKR) calculations. Similarly, we have studied how s- and p-polarization affect to the calculated spectra. These studies could help to reach a better understanding of photoemission measurements on MAPI.