The substituent effects on π-orbital energies in three benzene derivatives have been examined on the basis of data provided by HeI ultraviolet photoelectron spectroscopy (UPS). We focus on cooperative action of substituents when acting on the π-electrons of benzene ring. We present UPS of substituted benzenes: 4-methoxybenzoic acid (MBA), 2,3,5,6-tetramethyl-nitroaniline (TMNA) and pentafluorobenzaldehyde

A 90°-deflection imaging electron analyzer for measuring wide 2D angular distribution and perpendicular spin texture is proposed. This analyzer, which we call “right-angle-deflection imaging analyzer (RADIAN)”, provides electrostatic 90°-deflection and 2D focusing of an electron beam. Here a large acceptance angle comparable to that of cylindrical mirror analyzer (CMA) is achieved without using a grid

We have functionalized multiwall carbon nanotubes (MWCNTs) with the composition of SiO2 and TiO2 (MWCNTs:TiO2:SiO2) at different Ti:Si stoichiometric ratios (Ti:Si ≈ 6:6 at% and ≈10:10 at%) using the hydrothermal process. The micro-structural, electronic and electrical properties of the unfunctionalized and functionalized MWCNTs were studied. Changes in surface morphology, degree of hybridization,

The electronic structures of an unsaturated amide, thioamide and dithionoester have been studied in the gas phase by HeI photoelectron spectroscopy and quantum chemical calculations. The comparison of measured spectra with the spectra of related compounds reveals the effects of intramolecular interactions in these molecules. The electronic structures deduced from the spectra are then related to some

Core-hole creation and decay are of tremendous importance in both theory and applications. However, different ionization approaches and decay channels, especially at L-shell, bring many challenges to accurate simulation. In order to understand the ionization state effects on the creation and decay at L-shell hole, we performed a theoretical study of photon/electron-impact L-shell ionization of differently

There is a need to develop an automatic spectral analysis method integrated with reference database as the reference database builds up. At the time of spectral analysis, the compound ratio is often estimated by comparing a measured spectrum with reference spectra of known single-phase compound samples. However, it is difficult to automate all processes, and there is the problem that the operator's

Tungsten carbide-titanium carbide composite of six different compositions (in the range 1−15 wt% TiC) prepared by arc plasma melting has been evaluated for the first time by spectroscopic methods such as X-ray photoelectron spectroscopy (XPS), micro Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. From XPS, the presence of elements like W, Ti, C and O were identified unambiguously

We report on the calculation of the structural, electronic, magnetic and half-metal properties of the rocksalt CsTe compound using the first principles method which is based on density functional theory. Although this compound does not possess any transitional metal in its formula, it is found to carry the half-metallic ferromagnetic property at bulk as well as the surfaces. The energy gap is equal

Trace U species (i.e., ppm) found in the combined solid and liquid residues from uranium milling operations, known as tailings, are of scientific interest as tailings management facilities (TMFs) are designed to keep U species and other potentially harmful substances sequestered as solid species to limit exposure to the environment. Use of X-ray microprobe to study U within solid tailings is challenging

We have calculated atomic data such as energy levels, transition wavelengths, oscillator strengths, transition rates, lifetimes and Collision cross-section for Sn3+ and Sn4+ ions. We have employed Flexible atomic code (FAC) in our computations. We have computed lowest 31 and 17 fin. structure levels for Sn3+ and Sn4+ resp. We have provided transition data for all electric dipole (E1), magnetic dipole

The interaction of an ion with surrounding solvent molecules is revealed by X-ray absorption spectroscopy in transmission mode for the case of calcium dication dissolved in pure water, methanol and ethanol at the Ca K and L2,3-edges. The near-threshold K-shell excitation leads to two distinct solvent-dependent features, the Ca 1s to 3d and 4p electronic transitions, clearly indicating the ligand field

The angular distribution of Auger electron following photoionization in Xe atom is investigated using the multiconfiguration Dirac-Fock (MCDF) method and the density matrix theory. The alignment parameters of residual ions produced by the np3/2(n=2−5) and md3/2,5/2(m=3,4) sub-shell photoionization and the anisotropic angular parameters of Auger electron for different transition channels are calculated

Effect of Ca – doping on electronic structure and ferroelectric properties have been studied on PLD grown Bi1-xCaxFeO3/SNTO (x = 0.05, 0.10, 0.20) films. The structural study confirms single crystalline (100) oriented epitaxial growth of the films. The observed improvement in the ferroelectric behavior with an increase in Ca – doping has been attributed to the strong hybridization between Fe3d–O2p

Electron energy-loss spectra were measured in isoxazole in the excitation energy range 3.5−10 eV to investigate the valence excited states. Spectra recorded at different scattering conditions enabled the identification of the singlet and triplet states and the determination of their vertical excitation energies. The two lowest energy triplet bands, ππ* 13A' and ππ* 23A' at 4.20 and 5.30 eV, respectively

The thin oxide layers forming on the metal surfaces of metals determine their interactions with the environment and have a strong influence on the materials properties such as corrosion resistance. Such oxide layers typically have a thickness in the range of a few nanometres, which is a challenge for the analysis of their chemical nature and structure. To characterize such materials and surfaces, XPS

We analyzed two amorphous multilayer nanostructures (MLNS) [(CoFeB)60C40/SiO2]200 and [(CoFeB)34(SiO2)66/C]46 with the same element composition, but with the inverse location of the non-metallic phases C and SiO2 in the metal-composite layers or interlayers. Based on the analysis of XPS and X-ray absorption spectra, it was found that in the metal-composite layers the chemical bonds prevailing at the

The quest for mapping the femtosecond dynamics of the electronic band structure of complex materials over their full first Brillouin zone is pushing the development of schemes to efficiently generate ultrashort photon pulses in the VUV energy range. At present, the critical aspect in time- and angle-resolved photoelectron spectroscopy (TR-ARPES) is to combine a high photon energy with high photoemission

We report on the growth of a Fe/Co bilayer on W(110) and its electronic and magnetic structure characterization by means of low energy electron diffraction and spin-resolved photoemission spectroscopies. The Co bottom layer, investigated in the thickness range from 2 to 10 monolayers (ML), relaxes immediately to its bulk hcp structure and is therefore used to provide an hexagonal top surface for the

By using first-principles calculations, the electronic and optical properties of GeC sheet under strain have been investigated. The results demonstrate that both biaxial compressive and tensile strain change the band gap of GeC sheet. The capability of direct to indirect band gap transition is observed by exerting the in-plane biaxial strain on GeC sheet. Also, by applying the tensile (compressive)

Ultra-nano-crystalline diamond (UNCD) thin films with average thickness ∼200 nm, were grown on n-type mirror polished silicon (100) substrates using microwave plasma enhanced chemical vapour deposition system in different gas (H2 - N2 - Ar - CH4) composition plasma atmospheres at 1200 W (2.45 GHz) and in a pressure of 120 Torr with plasma-temperature ∼475 °C. Raman spectroscopy was used for microstructural

Acrylonitrile (ALN) and acetonitrile (ATN) are two important interstellar molecules that contain nitrogen atoms. Herein, we explore the proton transfer processes occurring in gaseous clusters of ALN and ATN molecules with the aid of synchrotron vacuum ultraviolet radiation. We investigated the proton transfer phenomenon by use of time-of-flight mass spectrometry as well as theoretical calculations

In this work, glycine-aided combustion synthesis of spinel-type MnCo2−xDyxO4 (x = 0.02, 0.04 and 0.06 %) nanocrystalline powders is presented. The mechanism involved in the chemical synthesis is briefly discussed. The integrity of the synthesized nanocrystalline powders was investigated and evaluated in correlation with dysprosium levels. Powder X-ray diffraction and Fourier-transform infrared spectroscopy

The electronic structure of 1,1-dithiomethyl-2-nitro-ethene (DTMNE) has been studied in the gas phase by HeI ultraviolet photoelectron spectroscopy and quantum chemical calculations. The comparison of the DTMNE spectrum with the spectra of related compounds: nitroethene, and 1,1-dithiamethyl-ethenes shows the intramolecular interactions between the nitro group, CC bond and thiomethyl groups. The electronic

The oxidation of UN0.1 was studied under UHV conditions with comparison to U and UN0.68, and the nitriding effect on the electronic structure is included. A doublet characteristic of U5d spectra is evident with significant signal at 94.3 eV in the nitride samples, which is attributed to the UN component. Similar to UN0.68, a correlative oxidation behavior of UN0.1 is identified, and the multistage

Energy level alignment at the interface of ZnO with monolayer sheets of graphene oxide (GO), reduced graphene oxide (RGO), and simultaneously reduced and doped graphene oxide by ammonia plasma treatment (APGO) have been investigated using the photoelectron spectroscopy. The difference in surface sensitivity of XPS and UPS has been utilized to deduce the energy band diagram. The measurements reveal

We investigate the magnetism and the electronic structure of body centred cubic, Fe0.8Ni0.2 alloy. While the magnetic moment of pure Fe and the alloy in bcc phase are almost similar, the hysteresis loop exhibits soft magnetic behavior. Transport measurements exhibit hysteresis in cooling and heating cycles indicating possibilities of structural change in the alloy. Photoemission results exhibit signature

This paper presents the electronic structure and optical behavior of Sn1-xFexO2 (0 % ≤ x ≤ 7 %) nanoparticles synthesized using co-precipitation assisted hydrothermal method. The structural properties of as-synthesized nanoparticles were examined using XRD and Raman spectroscopy. The XRD results demonstrated that all the samples are crystallized in tetragonal (rutile) crystal structure without any

Gold-implanted aluminum films are used to investigate how reflection electron energy loss spectra (REELS) change due to the presence of a small concentration of heavy atoms at a specific depth. Au ions were implanted with 30, 100 and 300 keV energy. REELS spectra were taken at energies between 10 and 40 keV. Large changes in the REELS spectra are observed after Au implantation, but the nature of the

The results of investigations conducted on the valence band structure of the near-surface atoms of niobium (Nb) sample, taken from a sheet that is used for fabricating superconducting radio frequency (SRF) cavity, are presented. The valence band electronic states were excited using low energy (≤50 eV) ultraviolet radiation. It was observed that a) the valence band spectrum primarily consists of oxygen

Recent developments yielding intense and short light pulses in the atto-second regime makes it possible to address fundamental questions on the time evolution of the electron dynamics. We demonstrate in our studies that electron pair emission from surfaces holds the promise to unravel the time scale of correlated electron dynamics. This can be achieved without atto-second light sources. We will discuss

Implementation of in-situ and operando experimental set-ups for bridging the pressure gap in characterization techniques based on monitoring of photoelectron emission has made significant achievements at several beamlines at Elettra synchrotron facility. These set-ups are now operational and have been successfully used to address unsolved issues exploring events occurring at solid–gas, solid–liquid

The development of ultra-bright extreme ultraviolet (EUV) and X-ray free electron laser (FEL) sources has enabled the extension of wave-mixing approaches into the short wavelength regime. Such a class of experiments relies upon nonlinear interactions among multiple light pulses offering a unique tool for exploring the dynamics of ultrafast processes and correlations between selected excitations at

A momentum resolved resonant inelastic X-ray scattering (qRIXS) experimental station with continuously rotatable spectrometers and parallel detection is designed to operate at different beamlines at synchrotron and free electron laser (FEL) facilities. This endstation, currently located at the Advanced Light Source (ALS), has five emission ports on the experimental chamber for mounting the high-throughput

The apex region of a capped (5,5) carbon nanotube (CNT) has been modelled with the DFT package ONETEP, using boundary conditions provided by a classical calculation with a conducting surface in place of the CNT. Results from the DFT solution include the spatial distribution of charge density, the changes to the highest occupied molecular orbital (HOMO) induced by an external field and a comparison

More than a century after the discovery of the electron, there are still fundamental, yet unresolved, questions concerning the generation-ejection mechanism of the ubiquitous Secondary Electrons (SEs) from a solid surface. Broadness of the field of application for these SEs makes it desirable to be able to control this phenomenon, which requires the understanding of the elementary physical mechanism

Three approaches for the measurement of charge density distributions in nanoscale materials from electron optical phase images recorded using off-axis electron holography are illustrated through the study of an electrically biased needle-shaped sample. We highlight the advantages of using a model-based iterative algorithm, which allows a priori information, such as the shape of the object and the influence

Two-dimensional materials, such as graphene, are usually prepared by chemical vapor deposition (CVD) on selected substrates, and their transfer is completed with a supporting layer, mostly polymethyl methacrylate (PMMA). Indeed, the PMMA has to be removed precisely to obtain the predicted superior properties of graphene after the transfer process. We demonstrate a new and effective technique to achieve

The study of Secondary Electron Yield (SEY) is widely performed to address important properties of materials to be used in a very wide spectrum of applications. It is, therefore, extremely important to understand the SEY dependence on material type, surface contaminants, structural quality and surface damage. We review here our recent studies of such items performed by looking at some representative

Time-of-flight spectrometer configurations combined with position sensitive single particle counting detectors have been simulated with a Monte Carlo code to find an efficient solution for coincident low energy electron detection. Photoemission experiments on polycrystalline silver have been performed at a synchrotron radiation facility with a likewise wide-angle ARPES (angle resolved photoemission

In the Fowler-Nordheim regime of Scanning Tunneling Microscopy (STM) the tip-target distance is few nanometers to few tens of nanometers. In this situation the tunneling between tip and target is completely suppressed. Instead, electrons can be field-emitted from the tip and their impact with the target might excite electrons off the surface. Under certain circumstances, the excited electrons escape

Graphene coated nickel electron sources have been recently reported to have significant advantages over state-of-the-art conventional tungsten cold field emission sources for electron microscopy/lithography applications. In this article, noise characteristics and lifetime measurements of a graphene-coated point-cathode emitter are presented in a vacuum chamber with a base pressure of 2×10−9 Torr. The

When the radius of curvature R of an electron emitter is below 5 nm existing theories of field emission from curved surfaces fail because they assume a constant supply of electrons which is a characteristic only of planar surface emitters. In a previous work of ours we proved that the eigenfuctions of a rotationally symmetric parabolic emitter-the common shape of present nanoscopic emitters- are Whittaker

First a brief description of the low energy electron microscope and its resolution limits is given. Then the beam-specimen interactions, which are important for the understanding of image formation are discussed. This is followed by a presentation of some examples of the application of LEEM and of the use of LEEM instruments for other imaging methods with low energy electrons.

Methods available for the mapping of dopants in silicon-based semiconductor structures with p-type as well as n-type doped patterns using low and very-low-energy electrons are reviewed together with the results of demonstration experiments.

Single crystalline tungsten oxides in a form of W5O14 and W18O49 nanowires were synthesized by iodine transport method. The morphology, work functions and field emission properties of these nanowires were investigated. Work functions of the W5O14 (4.20–4.34 eV) and W18O49 (4.55–4.57 eV) nanowires (NWs) have been measured by Kelvin probe force microscopy (KPFM) in ultra-high vacuum. Field emission (FE)

An investigation of the optical and electronic properties of amorphous silicon dioxide by means of a combination of reflection electron energy loss spectroscopy (REELS) and secondary electron–electron energy loss coincidence spectroscopy (SE2ELCS) is presented. Optical constants for a-SiO2 were extracted from the REELS measurements and a band gap of 9.1 eV was determined by deconvolution of multiple

Since the emission of secondary electrons for any incident energy always involves the formation and emission of a cascade of slow electrons (<50 eV) the secondary electron yield (SEY) for arbitrary energies depends sensitively on the inelastic mean free path (IMFP) values at low energies (below 100 eV). This makes it possible to retrieve the information about the low energy IMFP from high energy SEY

The interpretation of images generated by scanning electron microscopes (SEMs) requires quantifiable and well-understood contrast. Furthermore, recent interest in probing samples using low-energy electrons to extract surface information is pushing towards the quantification of relative contrast in secondary-electron (SE) images. The detection and analysis of low-energy SEs remains at the heart of the

The reduction of the total secondary electron emission during electron-matter interactions is required to improve the maximum power limit of the vacuum RF equipments prone to multipactor discharge. In this work, a chemical deposition technique was developed to create the appropriate micron or submicron surface roughness to significantly improve the typical characteristics of the flat silver coatings

A recent paper in this journal [B. V. Crist, J. Electron Spectrosc. Relat. Phenom. (in press)] describes current and historical calibration problems with core-electron binding energies (BEs) measured by X-ray photoelectron spectrometers and how these problems affect BE data in databases. Although Crist provides useful information about the variability of reported BE values, his article is incomplete

Treating Coulomb scattering of two free electrons in a stationary approach, we explore the momentum and spin entanglement created by the interaction. We show that a particular discretisation provides an estimate of the von Neumann entropy of the one-electron reduced density matrix from the experimentally accessible Shannon entropy. For spinless distinguishable electrons the entropy is sizeable at low

Energy and momentum distributions of correlated electron pairs excited by very low energy (9–30 eV) spin-polarized electrons from a thin Co film on a single crystal of W(110) were detected and analysed. Polarization of the incident electrons was perpendicular to the scattering plane. Spin effects are presented in form of asymmetry A = (I+ − I−)/(I+ + I−), where I+ and I− are two-electron spectra recorded

State-of-the-art spectroscopic techniques allow for a comprehensive understanding of one-electron excitations in various physically interesting and/or technologically relevant materials. While for weakly-correlated systems the corresponding one-particle spectral function A(ω, k) contains essentially all information about their physical properties the situation is much more complicated in the presence

First a brief description of the low energy electron microscope and its resolution limits is given. Then the beam-specimen interactions, which are important for the understanding of image formation are discussed. This is followed by a presentation of some examples of the application of LEEM and of the use of LEEM instruments for other imaging methods with low energy electrons.

Angle-resolved photoemission spectroscopy (ARPES) is the key momentum-resolved technique for direct probing of the electronic structure of a material. However, since it is highly surface-sensitive, it has been applied to a relatively small set of complex oxides that can be easily cleaved in ultra-high vacuum. Here we describe a new multi-module system at Brookhaven National Laboratory (BNL) in which

This review focuses on the use of X-ray absorption and emission spectroscopy techniques using hard X-rays to study electrocatalysts under in situ/operando conditions. We describe the importance and the versatility of methods in the study of electrodes in contact with the electrolytes, when being cycled through the catalytic potentials during the progress of the oxygen-evolution, oxygen reduction and

The effective attenuation length (EAL) is normally used in place of the inelastic mean free path (IMFP) to account for elastic-scattering effects when describing the attenuation of Auger electrons and photoelectrons from a planar substrate by an overlayer film. An EAL for quantitative determination of surface composition by Auger-electron spectroscopy (AES) or X-ray photoelectron spectroscopy (XPS)

The frontier orbitals of molecules are the prime determinants of their chemical, optical and electronic properties. Arguably, the most direct method of addressing the (filled) frontier orbitals is ultra-violet photoemission spectroscopy (UPS). Although UPS is a mature technique from the early 1970s on, the angular distribution of the photoemitted electrons was thought to be too complex to be analysed

Here we report on a combined experimental and theoretical study on the structural and electronic properties of a monolayer of Copper-Phthalocyanine (CuPc) on the Au(1 1 0) surface. Low-energy electron diffraction reveals a commensurate overlayer unit cell containing one adsorbate species. The azimuthal alignment of the CuPc molecule is revealed by comparing experimental constant binding energy (kxky

Self-assembled monolayers (SAMs) on gold prepared from amine-terminated alkanethiols have long been employed as model positively charged surfaces. Yet in previous studies significant amounts of unexpected oxygen containing species are always detected in amine terminated SAMs. Thus, the goal of this investigation was to determine the source of these oxygen species and minimize their presence in the