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[en] We study the electronic structure of p-trifluoromethylphenyl nitronyl nitroxide (p-CF3PNN), which forms a one-dimensional alternating antiferromagnetic chain of molecules, using angle-resolved photoemission spectroscopy. A singly occupied molecular orbital (SOMO) is observed clearly at ∼ 2 eV in the valence-band spectra. The small band gap and the overlap between the SOMO orbitals in the NO groups are associated with the antiferromagnetic interaction between neighboring spins.
[en] Photoemission spectroscopy (PES) has been used widely to study the electronic structure of valence and core levels. However, conventional PES is surface-sensitive. To probe the interface and bulk properties of materials, hard X-ray photoemission spectroscopy (HXPES) has received increasing interest in the last decade, because of the deep probing ability of photoelectrons with higher kinetic energies (2-10 keV). Recently, a HXPES system was developed at the Canadian Light Source, using the high-energy version of a R4000 electron analyzer-based spectrometer connected to a medium-energy beamline, the soft X-ray microcharacterization beamline (SXRMB). Excellent performance of the beamline and the spectrometer is demonstrated herein using Au Fermi and 4f core lines; and the controlled probing depth of HXPES at SXRMB is demonstrated by tuning the photon energy (2-9 keV) in the study of a series of SiO2/SiC multilayer samples. Combined with the high-resolution X-ray absorption spectroscopy available at the SXRMB, the HXPES offers a powerful nondestructive technique for studying bulk properties of various materials. (author)
[en] In this study, the effects of corona plasma process on the dyeability and certain physical properties of woolen fabric were investigated. For this purpose, acid and 1.2 metal complex dyes, which are the most applicable dyes in the wool market were used. The patterns were examined to assess their dyeability, wettability, pilling resistance, alkali solubility, and strength values. The surface morphology and chemical structures were tested by X-ray photoelectron spectroscopy and alkali solubility analyses and also scanned by electron microscopy. Hydrophility indexes of the dyes that were used were determined. With the results of the experiments, their hydrophobic index is of vital importance, which is a factor for plasma efficiency on color depth. By using plasma treatment on woolen fabric, it is achievable to get a product with high hydrophility and pilling resistance values, dyeability, and less burdened dyeing bath.
[en] Algorithms and methodologies for the calculation of Franck-Condon integrals are reviewed. Starting from the standard approach based on the Cartesian representation of the normal modes and the use of Duschinsky's transformation and recursion formulas, methods for treating large displacements of the equilibrium positions and anharmonic and non-Condon effects are considered. Finally, focusing attention on problems arising from the use of recurrence relations, some of the proposed solutions are critically reviewed along with new alternative approaches. (author)
[en] The aim of this study was to investigate the applicability of acoustic emission (AE) technique to evaluate delamination crack in glass/epoxy composite laminates under quasi-static and fatigue loading. To this aim, double cantilever beam specimens were subjected to mode I quasi-static and fatigue loading conditions and the generated AE signals were recorded during the tests. By analyzing the mechanical and AE results, an analytical correlation between the AE energy with the released strain energy and the crack growth was established. It was found that there is a 3rd degree polynomial correlation between the crack growth and the cumulative AE energy. Using this correlation the delamination crack growth was predicted under both the static and fatigue loading conditions. The predicted crack growth values was were in a good agreement with the visually recorded data during the tests. The results indicated that the proposed AE-based method has good applicability to evaluate the delamination crack growth under quasi-static and fatigue loading conditions, especially when the crack is embedded within the structure and could not be seen visually.
[en] Highlights: • Thiosemicarbazone derivatives as corrosion inhibitors for AA2024-T3 alloy. • Evaluation of inhibition efficiency by electrochemical methods. • Predominantly anodic inhibition, through adsorbed inhibitor layers. • Corroboration of experimental studies and theoretical studies. - Abstract: Three thiosemicarzone derivatives, namely (E)-2-(2-hydroxybenzylidene) hydrazinecarbothioamide(MHC), (E)-2-(2,4-dihydroxybenzylidene)hydrazinecarbothioamide (DHC) and (E)-2-(2,3,4-trihydroxybenzylidene)hydrazinecarbothioamide (THC) were synthesized and their corrosion inhibition action on 2024-T3 aluminum alloy was studied in 3.5% NaCl solution. The surface morphology and surface composition of the corroded alloy were examined using FESEM, 3D profilometry, EDX spectroscopy and X-ray photoelectron spectroscopy. The synthesized inhibitors were found to provide corrosion protection on AA2024-T3 by forming an adsorbed layer of the complex on the alloy surface. They exhibited inhibition efficiency in the order, MHC < DHC < THC. Quantum chemical calculations corroborated the experimental results.
[en] In high-temperature superconductors with a layered crystal structure out-of-plane contributions are often neglected, while the copper-oxygen planes are commonly considered to dominate the electronic properties around the Fermi energy. Here we report on a resonant photoemission study of (Pb,Bi)2201 and (Pb,Bi)2212 single crystals to unravel the resonant decay mechanisms at the Cu 2p absorption edge. We demonstrate a pronounced polarization dependence caused by two different Auger processes for in-plane and out-of-plane orientations. We deduce that the lowest energy valence state being involved in the two Auger processes, consists of three-dimensional contributions by admixed out-of-plane Sr, Bi, and O 2p states. It also suggests that the doping-induced charge density is dynamic, fluctuating within the Cu-O plane, and spills out perpendicular to it.
[en] In this work, the effects of different surface functional groups on the elemental mercury adsorption of porous carbons modified by chemical treatments were investigated. The surface properties of the treated carbons were observed by Boehm's titration and X-ray photoelectron spectroscopy (XPS). It was found that the textural properties, including specific surface area and pore structures, slightly decreased after the treatments, while the oxygen content of the ACs was predominantly enhanced. Elemental mercury adsorption behaviors of the acidtreated ACs were found to be four or three times better than those of non-treated ACs or base-treated ACs, respectively. This result indicates that the different compositions of surface functional groups can lead to the high elemental mercury adsorption capacity of the ACs. In case of the acid-treated ACs, the RC=O/RC-O and RCOOH/RC-O showed higher values than those of other samples, indicating that there is a considerable relationship between mercury adsorption and surface functional groups on the ACs
[en] Tracking edge-reflected acoustic emission (AE) waves can allow the localization of their sources. Specifically, in bounded isotropic plate structures, only one sensor may be used to perform these source localizations. The primary goal of this paper is to develop a three-step probabilistic framework to quantify the uncertainties associated with such single-sensor localizations. According to this framework, a probabilistic approach is first used to estimate the direct distances between AE sources and the sensor. Then, an analytical model is used to reconstruct the envelope of edge-reflected AE signals based on the source-to-sensor distance estimations and their first arrivals. Finally, the correlation between the probabilistically reconstructed envelopes and recorded AE signals are used to estimate confidence contours for the location of AE sources. To validate the proposed framework, Hsu-Nielsen pencil lead break (PLB) tests were performed on the surface as well as the edges of an aluminum plate. The localization results show that the estimated confidence contours surround the actual source locations. In addition, the performance of the framework was tested in a noisy environment simulated by two dummy transducers and an arbitrary wave generator. The results show that in low-noise environments, the shape and size of the confidence contours depend on the sources and their locations. However, at highly noisy environments, the size of the confidence contours monotonically increases with the noise floor. Such probabilistic results suggest that the proposed probabilistic framework could thus provide more comprehensive information regarding the location of AE sources. (paper)
[en] In this work we investigate the Renner-Teller effect (RTE) in the photoelectron spectra of ClCN and BrCN. The spectra were calculated by a nuclear wave packet propagation on coupled cationic surfaces obtained by the four-component Fock-space coupled cluster method. The scalar relativistic, spin-orbit and electron correlation effects are consistently included in the hypersurfaces for the three internal nuclear degrees of freedom. In contrast to other approaches no coupling matrix elements involving the spin-orbit operator together with an explicit representation of the wave function were necessary. The current study extends earlier work on the RTE for the derivation of the Renner-Teller parameters c and d where only one nuclear degree of freedom was considered (Pernpointner and Salopiata, 2013). The outlined procedure is especially useful for electronic structure methods that yield accurate energies but do not provide an explicit wave function representation.