AbstractX-ray photoelectron spectroscopy can be used to measure the ionization energies of electrons in both valence band and core orbitals. As core vacancies are the initial states for X-ray emission, a knowledge of their energies for all atoms in a mineral enables all the X-ray spectra to be placed on a common energy scale. X-ray spectra are atom specific and are governed by the dipole selection rule. Thus the individual bonding roles of the different atoms are revealed by the fine structure of valence X-ray peaks (i.e. peaks which result from electron transitions between valence band orbitals and core vacancies). The juxtaposition of such spectra enables the composition of the molecular orbitals that make up the chemical bonds of a mineral to be determined.Examples of this approach to the direct determination of electronic structure are given for silica, forsterite, brucite, and pyrite. Multi-electron effects and developments involving anisotropic X-ray emission from single crystals are also discussed.
ABSTRACTX-ray photoelectron spectroscopy of pure and K chemisorbed VxOy/TiO2 powders are reported. Core-line and valence band spectra suggest the presence of vanadium open shell ions on the pure VxOy/TiO2 interface, whereas potassium vanadate seems to form after K chemisorption. That results in the presence of a significant amount of gap states, with vanadium character, just above the O2p band edge, for the pure VxOy/TiO2 powder, while K chemisorption, reducing significantly the open shell vanadium ions, quenches the gap emission in the XPS valence band spectra.
— The electronic structure of hexagonal WO3 and triclinic CuWO4 nanocrystals, prospective materials for renewable energy production and functional devices, has been studied using the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) methods. The present XPS and XES results render that the W 5d-and O 2p-like states contribute throughout the whole valence-band region of the h-WO3 and CuWO4 nanocrystalline materialls, however maximum contributions of the O 2p-like states occur in the upper, whilst the W 5d-like states in the lower portions of the valence band, respectively.
On the basis of the X-ray photoelectron spectroscopy data and results of
theoretical calculations for the NpO2Cl4 (D4h) cluster, the electronic
structure and the chemical bond nature in , was done in the binding
Cs2NpO2Cl4 single crystal, containing the neptunyl group NpO2 energy range
of 0 eV to ~35 eV. The filled Np 5f electronic states were established to
form in the valence band of Cs2NpO2Cl4. This was attributed to the direct
participation of the Np 5f electrons in the chemical bonding. The Np
6p electrons were shown to participate in formation of both the
inner valence band (~15 eV-~35 eV) and the outer valence band (0 eV-~15
eV). The filled Np 6p and the O 2s, Cl 3s electronic shells were found to
make the largest contribution to the formation of the inner
valence molecular orbitals. The molecular orbitals composition and the
sequence order in the binding energy range 0 eV-~35 eV in Cs2NpO2Cl4, were
established. For the first time the quantitative scheme of
molecular orbitals for the NpO2Cl4 cluster in the binding energy range 0
eV-~35 eV, was built. This scheme reflects neptunium close environment in
the studied compound and is fundamental for both understanding the chemical
bond nature in Cs2NpO2Cl4 and the interpretation of other X-ray spectra
of Cs2NpO2Cl4. The contributions to the chemical binding for the
NpO2Cl4 cluster were evaluated to be: the outer valence molecular orbitals
contribution - 73 %, and the inner valence molecular orbitals contribution -
27 %.
AbstractX-ray photoelectron spectroscopy measurements and synchrotron radiation reflectivity and measurements in the photon energy range between 5eV and 30 eV are reported for yttrium stabilised zirconia single crystals. From the present data some behaviour of the valence band and conduction band electronic structure are elucidated. Two features present in the valence band XPS spectra, not explained on the basis of one-clectron theory, are tentatively assigned to simultaneous two electron excitation.
Carbon nitride materials require high temperatures (>500 °C) for their preparation, which entails substantial energy consumption. Furthermore, the high reaction temperature limits the materials’ processability and the control over their elemental composition. Therefore, alternative synthetic pathways that operate under milder conditions are still very much sought after. In this work, we prepared semiconductive carbon nitride (CN) polymers at low temperatures (300 °C) by carrying out the thermal condensation of triaminopyrimidine and acetoguanamine under a N2 atmosphere. These molecules are isomers: they display the same chemical formula but a different spatial distribution of their elements. X-ray photoelectron spectroscopy (XPS) experiments and electrochemical and photophysical characterization confirm that the initial spatial organization strongly determines the chemical composition and electronic structure of the materials, which, thanks to the preservation of functional groups in their surface, display excellent processability in liquid media.
Amorphous carbon nitride films ( a-CN x) were deposited by pulsed laser deposition of camphoric carbon target with different substrate temperatures (ST). The influence of ST on the synthesis of a-CN x films was investigated. The nitrogen-to-carbon (N/C) and oxygen-to-carbon (O/C) atomic ratios, bonding state, and microstructure of the deposited a-CN x films were characterized by X-ray photoelectron spectroscopy and were confirmed by other standard measurement techniques. The bonding states between C and N , and C and O in the deposited films were found to be significantly influenced by ST during the deposition process. The N/C and O/C atomic ratios of the a-CN x films reached the maximum value at 400°C. ST of 400°C was proposed to promote the desired sp 3-hybridized C and the C 3 N 4 phase. The C–N bonding of C–N , C=N and C≡N were observed in the films.
Electronic structure and chemical bond nature in Cs2NpO2Cl4