Application Of Electron Spectroscopy Research Articles

Design and characterization of Kerberos: a 48-channel analog pulse processing and data acquisition platform

A multi-channel data processing and acquisition system based on an analog ASIC (SFERA) has been designed and realized. The platform, called Kerberos, is suitable for the readout of large arrays of Silicon Drift Detector (SDD) for X-ray, γ-ray and electron spectroscopy applications. Each one of its 48 inputs is equipped with a 9th order semi-Gaussian shaping amplifier with programmable peaking time (0.5, 1, 2, 3, 4 and 6 ). The pulse amplitudes are multiplexed into three 16-bit high linearity SAR ADCs and digitized into an Artix-7 FPGA module. Kerberos will be used for the characterization of monolithic SDD matrices for the TRISTAN project. Many different readout strategies can be selected on Kerberos Graphic User Interface: for TRISTAN it has been decided to use a full detector readout strategy, with maximum input throughput of about 166 kcount/s. This work presents a full characterization of this scalable platform and its use with several detectors types (SDD, micro-strips) in X-ray, gamma and beta spectroscopy.

Application of Electronic Spectroscopy and Quantum-Chemical Modeling for Analysis of Products of Autoxidation of Adrenaline

The spontaneous oxidation of adrenaline in an alkaline medium was investigated by electronic spectroscopy. It was shown that the pH of the medium has an effect on the position of the maxima in the absorption spectrum of adrenaline. Analysis of the absorption spectra of the reaction medium during the oxidation process revealed the dynamics of change in the optical density of the products. The spectra of adrenaline, adrenolutine, and adrenochrome were calculated theoretically by quantum chemical methods within the scope of density functional theory. A procedure was developed for quantitative analysis of the products from autoxidation of adrenaline.

High-order harmonic generation at 4 MHz as a light source for time-of-flight photoemission spectroscopy

We demonstrate high-order harmonic generation (HHG) at 4 MHz driven by a long-cavity femtosecond laser oscillator. The laser output is used directly in a tight focusing geometry, where the harmonics are generated from a gas jet with high backing pressure. The harmonic light source is applied to time-of-flight photoemission spectroscopy, and the characteristic electronic structure of Cu(111) is measured. Our results suggest a straightforward design of high-order harmonic generation at megahertz repetition rate and pave the way for applications in electron spectroscopy and microscopy.

Electron spectroscopy of dilute nitrides

The application of electron spectroscopies in dilute nitride semiconductor research for bothchemical analysis and the determination of electronic and lattice vibrational properties isdescribed. X-ray photoelectron spectroscopy of the nitrogen bonding configurations in diluteInNxSb1−x andInNxAs1−x alloysis presented. High resolution electron-energy-loss spectroscopy (HREELS) of the plasmon excitationsin InNxSb1−x is shown to provide information on the electronic properties of the material, before andafter annealing. HREELS is also used to investigate the GaN-like phonon modes inGaNxAs1−x alloys.

Application of electron spectroscopy and surface modification techniques in the development of anti-microbial coatings for medical devices

Various gas plasmas were used to modify biomedical polymers (polyurethane and silicone) to examine the effect changes in hydrophilicity–surface functionality would have on bacterial adhesion and antibiotic retention. X-ray photoelectron spectroscopy (XPS) was used to characterise the modifications. Such treatments could reduce device-related infection on medical devices. While changes in hydrophilicty, as noted by changes in the contact angle, were seen for the various gas plasma (CO 2, H 2O and NH 3), these had little effect upon bacterial adhesion or antibiotic retention. An improvement was noted for antibiotic retention (ciprofloxacin) on the H 2O-plasma treated polyurethane, attributable to the presence of –OH groups, however, this was small. These results suggest that other approaches for reducing device-related infection be examined, such as the direct attachment of a drug-delivery system. To accomplish this for the drug-delivery system of choice, which utilises diisocynate chemistry, the introduction of primary amine groups onto the surface is required. Radiofrequency (RF) and remote microwave (MW) systems were used to introduce these groups onto both the biomedical polymer directly, and an intermediate, ethylene-based, plasma deposited film. The use of such a film would allow this technology to be applied to a variety of different substrates as well as provide a solvent barrier and a means of surface stabilisation. The MW system was found to be superior over the RF system in terms of deposition rate of the polymeric film, the effectiveness of its barrier properties and for the introduction of a higher proportion of primary amine functionality onto the surfaces as determined by XPS. Finally, use of a model system, in conjunction with XPS, confirmed the ability of these modified surfaces to be further derivatised using the isocyanate chemistry associated with the drug-delivery system. The results indicate that electron spectroscopy and surface modification techniques play an important and critical role towards the development of antimicrobial coatings for medical devices.

Identification of chemical components in XPS spectra and images using multivariate statistical analysis methods

A variety of data analysis methods can be used to enhance the information obtained from a measurement, or to simplify extraction of significant components from large data sets. Much work is needed to improve the quantification and interpretation of XPS spectra and images from complex organics. Multivariate analysis (MVA) is increasingly used for applications in electron spectroscopy to aid the analyst in interpreting the vast amount of information yielded by spectroscopic techniques. In general, the goals of MVA are to determine the number of components present, identify the chemical components, and quantify component concentrations in the mixture. Principal component analysis (PCA) is frequently used to determine the number of mathematical components which describe the data set. These mathematical components must then be related to chemically meaningful components. Various approaches to solve rotational ambiguities of spectral resolution, including local rank method (EFA), pure variables method (Simplisma) and multivariate curve resolution (MCR), are tested in the determination of chemical components from XPS data. Limitations associated with the resolution of a single matrix are shown to be partially or completely overcome when several related matrices are treated together. The test data sets contain XPS images or spectra acquired from blends of poly(vinyl chloride), PVC, and poly(methyl methacrylate), PMMA. The PVC degrades rapidly upon exposure to the X-ray beam. Spectra and images from the blend, acquired as a function of time, provide the multi-dimensional data sets for algorithm evaluation. In addition to spectral resolution, multivariate image analysis methods, such as principal component analysis, are used to extract maps of the pure components from an images-to-spectra data set.

Complexation of metal ions in brines: application of electronic spectroscopy in the study of the Cu(II)-LiCl-H2O system between 25 and 90°C

The concentration and transport of metals in hydrothermal solutions depend on how metals ions combine with ligands to form complexes, and experimental methods are necessary to identify the important complexes. UV-Vis-NIR spectrophotometry was used to study the formation of Cu(II)-chloride complexes in LiCl brines up to very high chlorinities (18 m LiCl), at temperatures between 25°C and 90°C. The number of Cu(II)-chloride complexes necessary to account for the variation in spectra with varying chloride molality at each temperature was estimated using principal component analysis. The molar absorptivity coefficients and concentrations of each complex were then determined using a “model-free” analysis, which does not require any assumption about the chemistry of the system, other than the number of absorbing species present. Subsequently, the results from the “model-free” analysis were integrated with independent experimental evidence to develop a thermodynamic speciation model, where the logarithms of the equilibrium constants for Cu(II)-chloride formation reactions were fitted to the data using a non-linear least-squares approach. Maps of the residual function were used to estimate uncertainties in the fitted equilibrium constants.The results of this study are similar to published properties of distorted octahedral [CuCl(OH2)5]+ and [CuCl2(OH2)4]0 at all temperatures, but diverge for [CuCl3(OH2)3]− and distorted tetrahedral [CuCl4]2−. Moreover, the data suggest the presence of [CuCl5]3−, probably with D3h point group, at very high salt concentration. This study demonstrates that it is possible to determine apparent thermodynamic equilibrium constants for the formation of complexes of trace amount of metals in highly concentrated brines, such as those associated with many ore deposits. The results are dependent on the choice of activity coefficients for charged and neutral aqueous complexes, but this influence is relatively small compared with the experimental uncertainty. This study shows that Cu2+ chloro-complexes, predominantly [CuCl2(OH2)4]0 and [CuCl4]2−, will play a dominant role in nature where free oxygen is available (near-surface), and where chloride activities are very high (evaporitic basins; hypersaline soils).

Mechanism of alkali promotion in heterogeneous catalysis under realistic conditions: application of electron spectroscopy and electrochemical promotion to the reduction of NO by CO and by propene over rhodium

XPS and Δφ measurements demonstrate that the potential of a Rh thin film in contact with a Na+ conducting solid electrolyte may be used to control ϑNa and hence the catalytic behaviour of the Rh surface. The system response is reversible and reproducible, catalyst work function and Na coverage varying linearly with catalyst potential over the experimentally accessible range. Coordinated reactor studies show that in the catalytic reduction of NO by CO or propene promotion is due to Na-induced NO dissociation, which process is the rate limiting step. As a result, very large increases in N2 selectivity may be achieved, along with useful increases in activity.

Application of XPS and factor analysis for non-conducting materials

Data analysis with multivariate mathematical methods is commonly used more and more also for applications in electron spectroscopy. This paper concerns the use of factor analysis in x-ray photoelectron spectroscopy and is focused on the problems occurring during investigations of non-conducting materials. Possibilities of the correction of the charging effect are discussed, considering the aspects of background subtraction and spectra concatenation. The efforts of the proposed procedures are demonstrated with model experiments and depth profile measurements. © 1997 John Wiley & Sons, Ltd.

Metal Oxide Surfaces: Electronic Structure and Molecular Adsorption

AbstractThe surface science of oxides has received considerably less attention than the study of metal surfaces. We review some of our work on structural characterization and electronic structure investigations on oxide surfaces which we prepare as thin oxide films on metallic substrates. This preparation method leads to certain experimental advantages concerning the application of electron spectroscopies on such systems. We discuss molecular adsorption on non‐polar and polar surfaces of clean oxides. The influence of metal deposition onto the oxide surfaces and on their properties with respect to adsorption is described. Light induced processes with full quantum state detection of desorbing molecules are addressed. The possibility of studying dynamic processes in adsorbates on oxides via electron spin resonance spectroscopy is evaluated.

A new method for quantitative analysis of EELS

Techniques to remove plural scattering from electron energy loss spectra (EELS) are important in bot hmicroanalysis and other quantitative applications of electron spectroscopy. The techniques used are either based on convolution, or Fourier transform deconvolution, methods, in which either the elastic scattering angular correction or both elastic and inelastic angular corrections are not included. In this work we propose a new method based on both angular and energy loss three-dimension Poisson statistics which includes elastic and inelastic mixed angular scattering correction in order to obtain more accurate quantitative analysis for EELS.The electron scattering distribution determined by angular and energy loss three-dimension Poissonstatistics is given by:where ITis the total incident electron intensity; t is the sample thickness; λi, λeand λTare inelastic , elastic and total scattering mean free paths; Si(θ) and Se(θ) are normalized single inelastic and elastic angular scattering distributions respectively, F(E) is the single scattering normalized energy loss distribution.

Smoothing by spline functions: applications in electron spectroscopy

This preliminary investigation deals with the use of spline functions for smoothing spectral data. Three variant implementations are outlined and some tentative results are presented.

Electron optical characteristics of negative electron affinity cathodes

Stable continuous electron emission has been obtained from GaAs electron cathodes which have been activated to a negative electron affinity condition. Negative electron affinity (NEA) photocathodes offer one means of producing very short electron pulses with a high peak brightness necessary for time-resolved metrology. Despite concerns regarding the stability of such cathodes, we have demonstrated a high degree of short-term stability through the ability to take scanning electron microscope photographs and Auger spectra using a NEA cathode. We have also demonstrated an effective brightness measured at the sample of 1×105 A/cm2 sr at 3 kV using our prototype electron gun. Room-temperature operation and laser excitation of this cathode make it particularly well-suited for low-voltage time-resolved electron probe and electron spectroscopy applications.

Quantum-chemical investigation of the application of electron spectroscopy for identification of the nature of acidic and basic sites on a surface

This paper presents quantum-chemical calculations for the electron absorption spectra of p-aminoazobenzene (p-AAB) and its compounds with active surface sites (protons, water molecules, hydroxyl groups, aquacompounds of exchanged cations, and lewis acidic sites) to determine the applicability of electron spectroscopy for identifying the nature of acidic-basic sites. The most significant result of the analysis of the electron spectra of p-AAB and its complexes with different active surface sites is that the application of electrouspectroscopy does not typically allow one to distinguish between proton and aproton sites and, in some cases, between acidic and basic sites.

Applications of electron spectroscopy in materials science

The effects of several phenothiazine derivatives (PTDs) and quinidine (QD) on the jejunal microclimate-pH in rats were studied using a microelectrode. Chlorpromazine, thioridazine, chlorpromazine sulfoxide (CPZSO), trifluoperazine, prochlorperazine, and QD at concentrations of 1 mM increased this microclimate-pH by 0.15–0.3 pH units, while 1 mM diethazine and 1 mM promethazine had little effect on it. The increases in the microclimate-pH caused by PTDs and QD were concentration dependent and reversible. We studied the effects of PTDs on the fluidity of intestinal brush border membranes and on the release of proteins from the intestinal tissue to the lumen. The PTD-induced changes in microclimate-pH could not be explained by either of these nonspecific effects on the membranes. Then, the effects of PTDs on Na+, K+-ATPase activity and Mg2+-ATPase activity were studied using the jejunal homogenate. Each PTD inhibited Na+, K+-ATPase and Mg2+-ATPase activity to some extent. The inhibitory effects on Na+, K+-ATPase and Mg2+-ATPase activity were compared with the PTD-induced increases in the microclimate-pH. No good correlation was obtained between the IC50 values of PTDs for Na+, K+-ATPase activity and the concentrations required to increase the microclimate-pH by 0.1 pH unit, while IC50 values of PTDs for Mg2+-ATPase activity showed a relatively good correlation, except for that of CPZSO. These findings suggest that the effects of PTDs on the microclimate-pH were not nonspecific, although the increases in the microclimate-pH caused by PTDs cannot be fully explained by the inhibitory effects of these compounds on either Na+, K+-ATPase activity or Mg2+-ATPase activity alone.

Application of Electron Spectroscopy for Chemical Analysis (ESCA) to the study of iron-based battery electrodes

Electron Spectroscopy for Chemical Analysis (ESCA) has been used in combination with X-ray diffraction (XRD) and energy-dispersive X-ray analysis (EDAX) to study the oxidation state, structure and morpholog of pure iron and iron-cadmium electrodes in various stages of cycling. The electrodes have only been studied in their discharged state. Cycling produces particle coarsening and a change in phase composition of the iron compounds from Fe3O4 toα-Fe. ESCA spectra suggest that a thin cadmium-rich surface film of poor electronic conductivity forms on the surface of the particles after prolonged cycling.

Electron spectroscopic evidence of the thiolsulphonate structure of cystine S-dioxide

Application of electron spectroscopy (ESCA) has directly and conclusively proved, that cystine S-dioxide possesses a thiolsulfonate structure.