Littérature scientifique sur le sujet « Cu 2p »

The electronic density of states (DOS) of both pure and Co-substituted YBa 2 Cu 3 O 7 has been calculated by a recursion method. The results show that the total DOS at the Fermi level of YBa 2 Cu 3 O 7 mainly comes from the contributions of the O 2p and Cu 3d orbitals. After Co doping, the O 2p–Cu 3d bonds are destroyed while the O 2p–Co 3d bonds are formed at lower energies, and the total DOS at the Fermi level decreases strikingly. In addition, our results reveal that the CuO chain has a one-dimensional feature.

In this paper, we describe the synthesis of Ni/SiO₂and Ni–Cu/SiO₂catalysts derived from phyllosilicate structures (Ni/SiO_2Pand Ni–Cu/SiO_2P, respectively) for steam reforming of biomass tar reaction.

Synchrotron XPS and Cu L2,3-edge NEXAFS spectroscopic data for a natural tetrahedrite surface prepared by fracture under UHV were in accord with the composition of the mineral and its expected semiconductivity. The 2p binding energy for the 6-coordinate S atoms was found to be not detectably greater than that for the 4-coordinate S atoms, and surface species were not clearly discernible in either surface-optimized S 2p or Cu 2p spectra. The Cu 2p and Cu L2,3-edge spectra indicated that all Cu in the mineral was indisputably Cu(I). The Cu L2,3-edge spectra of relatively pure natural sphalerite treated with mildly acidic aqueous cupric solution revealed the presence of Cu(II) in the outermost layer of the fracture surfaces, but it was concluded that most of the Cu near the surface of the mineral was in formal oxidation state Cu(I), albeit with higher than normal d9 character. The Cu(I) absorption peak was at an energy much lower than for the tetrahedrite absorption edge, but still consistent with Cu(I) in 4-fold coordination by S. The Cu(II) was consistent with Cu bonded both to S atoms in the outermost layer of the sphalerite and to O atoms in chemisorbed water. S 2p spectra determined at different photon energies revealed high binding energy components arising from oligosulfide-like environments in the outermost layers, but not necessarily in a completely restructured lattice and not in a Cu oligosulfide only. The data indicated some loss of Zn in addition to the Zn that had been replaced by Cu in the outermost layers of the sulfide lattice. The presence of these oligosulfide-like environments precluded the detection of S with formal oxidation state greater than (-II) that might have arisen only from Cu(I) in the S lattice. No evidence was obtained for the presence of Cu(II) in a sulfide lattice, but it was not possible to exclude the possibility of a very low concentration because of the presence of the Cu(II) bonded to both S and O at the surface of the treated sphalerite.Key words: tetrahedrite, sphalerite, copper uptake, XPS, NEXAFS.

Cu , Al , and Ti films of ~ 10 nm thickness were deposited on porous silicon (PS) at room temperature using Filtered Cathodic Vacuum Arc system and annealed at 800°C for 10 min in vacuum. The PS layers were obtained by anodization of Si wafer. X-ray photoelectron spectroscopy, photoluminescence (PL), photo-absorption (PA), and X-ray diffraction studies revealed that before annealing just Cu -deposited sample exhibited PL blueshift, PA redshift, and Si -2p level shift due to the Cu diffusion at the surface of PS. While after annealing, Cu - and Ti -deposited samples exhibited obvious PA redshift and Si -2p level shift, which arise from the crystal field variation due to the formation of Cu / Ti silicides at the surface as well as the conduction electronic transportation.

Employing the new nitronyl nitroxide biradical ligand biNIT-3Py-5-Ph (2-(5-phenyl-3-pyridyl)-bis(4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide)), a 16-spin Cu-radical complex, [Cu8(biNIT-3Py-5-Ph)4(hfac)16] 1, and three 2p-3d-4f chain complexes, {[Ln(hfac)3][Cu(hfac)2]2(biNIT-3Py-5-Ph)2}n (LnⅢ= Gd 2, Tb 3, Dy 4; hfac = hexafluoroacetylacetonate), have been prepared and characterized. X-ray crystallographic analysis revealed in all derivatives a common cyclic [Cu-biNIT]2 secondary building unit in which two bi-NIT-3Py-5-Ph biradical ligands and two CuII ions are associated via the pyridine N atoms and NO units. For complex 1, two such units assemble with four additional CuII ions to form a discrete complex involving 16 S = 1/2 spin centers. For complexes 2–4, the [Cu-biNIT]2 units are linked by LnIII ions via NO groups in a 1D coordination polymer. Magnetic studies show that the coordination of the aminoxyl groups with Cu or Ln ions results in behaviors combining ferromagnetic and antiferromagnetic interactions. No slow magnetic relaxation behavior was observed for Tb and Dy derivatives.

The x-ray photoemission spectroscopie (XPS) data from different pelletized samples of the 90 K superconductor Ba2YCu3O7−δ (where δ∼0.2) have been obtained. The valence band spectrum (recorded at 300 and 170 K), which is composed of contributions from both the Cu 3d and O 2p levels, is compared with the full potential linearized augmented plane wave (FLAPW) calculated electronic density-of-states (DOS) reported by Massidda et al. and Mattheiss and Hamann. The experimental data indicate a relatively low DOS at the Fermi level. Detailed measurements of the core level Cu 2p, O 1s, Ba 3d, 4d, and Y 3d spectra of the superconducting and related standard materials, are presented. Data for the superconducting material were recorded in the freshly prepared form as well as after scraping in situ. The Cu 2p core level, satellite, and Auger spectra for the various samples were carefully examined in order to assess the possibility of the presence of Cu3+ ions in Ba2YCu3O7-δ. It is observed that surface reaction in air to form carbonates and hydroxides occurs readily in the superconducting material.

Ternary carbide in metal matrix composites constitute a big challenge in the industry, and in this regard their surface treatment is one of the most important issues. Ternary carbide (CuxTiyCz, where x, y and z are integers) thin films are synthesized by magnetron sputtering and characterized with respect to the film depth. X-ray photoelectron spectroscopy (XPS) of Cu-2p and Ti-2p peaks shows the associated shake-up satellite peaks at a smaller film depth; the peak intensity is reduced at a higher depth. The relative intensity of Cu and Ti increases at a larger film depth. The optical band gap varies from 1.83 to 2.20 eV at different film depths.

Dans le cas des spectres de photoélectrons Cu2p induits par rayons X , la présence de rayons satellites sert d'indication d'un état d'oxydation Cu(II). L'existence de signatures satellites dans les composés de métaux de transition 3D (TM) a suscité de nombreux débats et controverses, conduisant à la proposition de théories contradictoires. Notre approche offre une explication alternative au modèle à transfert de charge pour la formation des états ionisés de cœur permettant d'expliquer l'origine des images. Grâce à un développement théorique approfondi et à la mise en œuvre d'un code numérique incorporant les effets de relaxation et corrélation électroniques ainsi que les effets relativistes de couplage spin-orbite, les bandes satellites des spectres de niveau de cœur Cu2p de Cu(II) sont assignés à un ensemble d'excitations secondaires de type ”shake-up”, dans lesquelles un électron des couches de valence est excité vers l'orbitale moléculaire simplement occupée (SOMO) la plus externe. Grâce aux développements théoriques (formules analytiques, optimisation de bases, code CI maison), nous soulignons que l’intensité des bandes est gouvernée, dans l'approximation soudaine, par le recouvrement entre les déterminants de Slater associés aux configurations initiales ( N-1) et (N-1) finales en utilisant la procédure Lowdin (LD) de recouvrement déterminants. Notre protocole numérique et nos développements analytiques ont été appliqués avec succès aux cas atomiques sur une série de configurations Cu nl −13d10 ou Cunl−13d9 (nl=2p, 3s, 3p). Dans les systèmes moléculaires, la description de la modification de la liaison chimique entre l'état initial et l'état final est d'écriture à l'aide d'une vision originale. Dans l'état initial, l'interaction Métal/Ligand s’opère entre le cation Cu 2+ (3d94s0) et le ligand (anionique) [X]2−, ou la LUMO du ligand est rempli par deux électrons provenant des orbitales Cu4s/Cu3d. La liaison chimique génère alors une orbitale moléculaire anti-liante (AB) fortement localisée sur l'orbitale Cu3d x2−y2 et une MO (B) liante (localisée sur la LUMO du ligand) d'énergie profonde. La création d'un trou de cœur Cu2p entraîne une modification importante de la nature de la SOMO. Dans l'état final, la pénétration plus importante des niveaux d'énergies Cu3d par rapport aux orbitales du ligand conduit à un changement de caractère de la SOMO qui ressemble alors à la LUMO du ligand. Inversement, dans l'état final, l'orbitale liée (B) présente un caractère métallique prononcé (Cu3dx2−y2 ). L'intensité de la bande principale du spectre Cu2p, régie par le recouvrement entre le SOMO dans l'état initial et la SOMO dans l'état final, dépend du degré de localisation de la SOMO sur la LUMO du ligand. La bande satellite dans les spectres est attribuée à des transitions shake-up ou un électron des couches de valence est promu sur la SOMO. L'intensité de la bande satellite dépend alors du caractère Cu3d `x2−y2 de la SOMO dans l'état initial. L'application de notre approche aux dihalogénures de cuivre montre que pour (Br, Cl), de faibles électronégativités, la présence d'un trou Cu2p provoque une interaction non liée entre les orbitales Cu3d du métal et les orbitales du ligand. Les niveaux d'énergie Cu3d du cuivre deviennent quasi-dégénérés comme dans le cas atomique Cu(II) et la bande satellite présente un profil analogique à celui observé pour la configuration atomique Cu 2p3/23d9. Inversement, dans les composes avec une électron/négativité élevée (O, F), la séparation Cu3d/L est plus modérée, conduisant à la génération de nouvelles MOs liante/antiliante. La forme du satellite est perturbée
In the case of Cu2p x-ray photoelectron spectra, the presence of satellite lines serves as a distinct indication of a Cu(II) oxidation state. The existence of satellite signatures in 3d transition metal (TM) compounds has sparked considerable debate and controversy, leading to the proposal of conflicting theories. Our developed approach offers an alternative explanation to the charge transfer model for the formation of core-ionized states that can explain the origin of the main and satellite peaks. Thanks to a thorough theoretical development and implementation of a numeric code incorporating relaxation/correlation electronic effects and spin-orbit coupling, the satellite bands in the Cu2p core level spectra of Cu(II) are assigned to a set of secondary excitations called ”shake-up” transitions, wherein one electron from the valence shells is excited to the outermost Singly Occupied Molecular Orbital (SOMO). Thanks to theoretical developments (analytic, basis set optimization, in-house CI code), we emphasize that the intensities line in core-level spectra are governed, in the sudden approximation, by overlaps between (N-1) initial and (N-1) final Slater determinants utilizing the Lowdin Determinant (LD) overlap procedure. Our theoretical numerical protocol and analytical developments were first successfully applied to atomic cases on a series of core-hole configurations, namely Cunl−13d10 or Cunl−13d9(nl=2p,3s, 3p). In molecular systems, the description of the modification of the chemical bond between the initial state and the final state is described using an original vision. In the initial state, the Metal/Ligand interaction operates between a Cu2+ (3d94s0) cation and an (anionic) ligand [X]2−, where the LUMO of the ligand moiety is filled by two electrons coming from the Cu4s/Cu3d orbitals. The chemical bond generates a high-energy singly occupied anti-bonding (AB) molecular orbital (SOMO) strongly localized on the Cu3dx2−y2 orbital and its bonding (B) MO counterpart (localized on the LUMO of the ligand) at deep energy. The creation of a Cu inner-shell vacancy leads to a significant alteration in the nature of the SOMO. In the core-ionized state, the larger drop in the energy of the Cu3d levels makes the SOMO undergoes a change of character to become very similar to the LUMO of the ligand. Conversely, the deeper bonding MO exhibits a pronounced metal character (Cu3dx2−y2 ) in the core-ionized state. It is shown that the main peak in the XPS spectra corresponds to the final Cu3d10 configuration with a single electron in the SOMO. It is stated that the intensity of the main line governed by the square overlap between the SOMO in the initial state and the SOMO’ in the final state depends on the degree of localization on the Ligand of the SOMO. The satellite line in the spectra is attributed to shake-up transitions where one electron from the valence shells is promoted to the SOMO’ where the intensity of the peak depends on the Cu3dx2−y2 character of the SOMO in the initial state. The application of our approach to copper dihalides shows that for (Br, Cl) with low electronegativity, inner-shell vacancies causes nonbonding interactions between the Cu3d and ligand molecular orbitals. The Cu3d energy levels become quasi-degenerate as in the atomic Cu(II) case, and the satellite band presents a profile analogous to that observed for the Cu 2p3/23d9 atomic configuration. Conversely, in compounds with higher electronegativity (O, F), the Cu3d/L separation is more moderate, leading to the generation of new bonding and anti-bonding MOs, and the satellite shape is more upset

The copper (II) oxide nanofibers (NFs) synthesized with the electrospinning method showed a necklace-like morphology and nanometric size. The use of the XPS (X-ray Photoelectronic Spectroscopy) technique allowed the analysis of the Cu 2p and O 1s orbitals showing a CuxO type stoichiometry (x = 1, 2, 3), in turn, the UPS (Ultraviolet Photoelectronic Spectroscopy) region determined the conduction state associated to the dielectric function. These data are compared with the EELS technique. The NFs have presented a behavior with double magnetic phase associated to the non-stoichiometry and oxygen vacancies, and the non-presence of the AFM phase due to the increase of the vacancies. In addition, their electronic and magnetic structure reveal spin-orbit related changes shown in the Cu 2p spectra. The results showed in the conduction band holes and the Cu 2p and O 1s orbitals.

Our experimental studies of the optical emission from the Cu-vapor laser indicate a breakup of laser pulse into oscillatory structures in certain conditions. We believe this phenomenon is similar to the optical ringing reported earlier.1 We attribute this breakup of the pulse to cooperative effects involved in emission from the Cu-vapor laser.2 This effect is further enhanced by propagation through the system. We earlier explained the high gain of Cu-vapor due to radiation trapping and Rabi oscillation between the 2P and 2S states.3 This analysis further shows that a large percentage of Cu atoms in the lasing medium are in the excited state (2P) most of the time. Therefore, there is a very low probability for total depletion of this level. This implies that the phenomena like gain switching and relaxation oscillation may not play a significant role in the breakup of the laser pulse. The oscillatory structures for both the 510.6-nm and 578.2-nm lines were strongly dependent on the changes in operating temperature. We observed the breakup of the pulse mainly around the temperature of 1600°C.