Chemical Shift In Binding Energy Research Articles

Separation of surface oxide from bulk Ni by selective Ni 3p photoelectron spectroscopy for chemical analysis in coincidence with Ni M-edge Auger electrons

The chemical shift of core level binding energies makes electron spectroscopy for chemical analysis (ESCA) a workhorse analytical tool for science and industry. For some elements, close lying and overlapping spectral features within the natural life time broadening restrict applications. We establish how the core level binding energy chemical shift can be picked up experimentally by the additional selectivity through Auger electron photoelectron coincidence spectroscopy (APECS). Coincident measurement of Ni 3p photoemission with different MVV Auger regions from specific decay channels, narrows the 3p core-levels to a width of 1.2 eV, resolves the spin–orbit splitting of 1.6 eV and determines the chemical shift of Ni 3p levels of a Ni(111) single crystal and its oxidized surface layer to 0.6 eV.

Physical genetics: Cross-breeding density functional theory and X-ray photoelectron spectroscopy to rationalize chemical shifts of binding energies in solid compounds

Like other spectroscopic methods XPS and AES show characteristic chemical shifts depending on the elemental matrix of a compound, however, a satisfactory rationalization of the variance of such values is often difficult. By an extension of a previous approach we present a theory in a unifying equation which combines several parameters - some of them resulting from DFT calculations - which influence the energy of the outgoing electrons and thereby seemingly the binding energy. By calculating Bader charges, atomic volumes and site potentials we have produced a data basis for a set of chalcogenides and halides of Ba, Zn, Pb and Cu to rationalize the spread of measured binding energies and Auger energies. It has thereby become possible to quantify different factors separately which bias the measurement of the kinetic energies of the outgoing core electrons, both the photo-emitted and the Auger electrons. Such an analysis can also trace special features of an open-shell configuration and even show up effects of a semiconductor-type.

Photoluminescence and XPS analyses of Mn 2+ doped ZnS nanocrystals embedded in sol–gel derived hybrid coatings

Photoluminescence and X-ray photoelectron spectroscopy studies of Mn 2+ doped ZnS nanocrystals in inorganic–organic hybrid coatings prepared by a sol–gel process are presented. A 25-fold enhancement of photoluminescence was observed after UV irradiation for 6 h in an ambient atmosphere. X-ray photoelectron spectroscopy results indicate a chemical shift of binding energy from ZnS to ZnSO 4 after UV irradiation. X-ray diffraction results show a decrease of ZnS nanocrystal size during UV irradiation. The cause of these phenomena was discussed based on a photochemical reaction on ZnS nanocrystal surface.

Study on the coating of nano-scale SiO2 film on the surface of nanocrystalline Mg-Al layered double hydroxides

The coating process of a nano-scale SiO 2 film on the nanocrystalline Mg-Al layered double hy-droxides via a sol-gel process was investigated. The uniform and dense SiO 2 film with a thickness of about 5 nm on the nano-LDHs particles was characterized by the solubility test in the dilute HNO3 or HCl acid, TEM and FT-IR, XRD, TG and DSC. The chemical shifts of binding en-ergies of Al 2p, Mg 2p, Si 2s and O 1s on the coated particles indicate that the coating of the SiO2 nano-film on the surface of the nano-LDHs proceeds through the formation of Mg-O-Si and Al-O-Si bonds. The thermal analysis shows that both the SiO 2 -coated nano-LDHs and the nano-LDHs have a similar mass loss process, in which there are three obvious stages of mass loss in the temperature range of 40—700℃. Furthermore, the more the coated amount of SiO 2 on the surface of the nano-LDHs is, the less the mass loss of the samples is at 700℃.The nano- LDHs have two obvious endothermic peaks at 244.67℃ and 430.13℃, whose corresponding heat absorption capacities are 412.28 J/g and 336.30 J/g, respectively. In contrast, the coated nano-LDHs have only one endothermic peak at 243.60℃ with a heat absorption capacity of 221.25 J/g.

Surface characteristics of hydrous silica-coated TiO 2 particles

The surface characteristics of hydrous silica-coated TiO 2 particles are experimentally studied. Different analytical techniques were used to characterize the Si oxide coatings on TiO 2 particles. The high-resolution transmission electron microscope (HRTEM), ζ-potential analyzer and X-ray photoelectron spectroscope (XPS) analyses show that hydrous silica is continuously coated on the surface of TiO 2 particles. From the chemical shift of binding energy of O 1s and Ti2p 3/2 on coated particles and FTIR analyses of absorption band, it is inferred that Si oxide in the coating film is combined onto TiO 2 particle surface through chemical bond of Ti–O–Si. The electrokinetic behavior of TiO 2 particles can be modified significantly by dense film coating.

XPS study of the L-CVD deposited SnO 2 thin films exposed to oxygen and hydrogen

In this paper, the XPS study of SnO 2 thin films deposited by the L-CVD technique are presented. The influence of exposition of the as-deposited samples to oxygen O 2 and hydrogen H 2 on their stoichiometry was determined. Moreover, on the basis of detailed shape analysis of the Sn3d 5/2 and O1s XPS peaks, the chemical shift of binding energy corresponding to the change of sample stoichiometry was separated from a shift of the binding energy corresponding to the change of interface Fermi level position E F– E v in the band gap, using a new procedure of deconvolution of the core level XPS peaks. The shift of the Sn3d 5/2 peak by approximately 0.5 eV towards the lower binding energy after highest H 2 exposure was interpreted as a true chemical shift due to an increase of Sn 2+ component, whereas the shift of Sn3d 5/2 peak and O1s peak after highest O 2 exposure by approximately 0.5 eV towards the lower binding energy was interpreted as a result of the shift of the interface Fermi level position in the band gap towards the top of valence band at the surface, which corresponds to a deep accumulation layer typical for SnO 2 thin films.

Synergistic effect of mineral surface constituents in dextrin adsorption

The present work is a part of a systematic research on the interaction mechanism between polysaccharides and mineral surfaces, and deals with the adsorption of dextrin onto oxide and salt-type minerals. The minerals tested include hematite, rutile, fluorite, calcite, apatite, etc. It is observed that dextrin adsorption on these minerals is strongly pH-dependent, with high adsorption densities at pH values around the isoelectric points of the minerals, which indicates interactions with surface metal hydroxide species. X-ray photoelectron spectroscopy (XPS) and Auger Electron Spectroscopy (AES) measurements reveal chemical shifts of binding energies of core electrons, or chemical shifts of modified Auger parameters of mineral surface elements after dextrin adsorption, pointing to a chemical mechanism of interaction. Furthermore, it is observed that the reaction of minerals with moderate amounts of fatty acids prior to dextrin addition results in an increase in dextrin adsorption, whereas reaction with excessive fatty acids prior to dextrin addition results in a decrease in dextrin adsorption. In the light of the results of our previous studies, and also from the experimental observations of the present work, it is concluded that although surface hydrophobic species alone do not have any significant effect on dextrin adsorption, they synergistically enhance dextrin adsorption when present together with surface metallic sites.

Chemical shifts of the core-level binding energies for the alkaline-earth oxides

Cluster model wavefunctions for the alkaline-earth oxides are analyzed to determine the origin of the trend of the chemical shifts of the binding energies, BEs, of the metal core levels. Two cancelling initial states mechanisms in the oxides are responsible for the trend. One is the increase of the BEs for the dication over the neutral atom. The second is the decrease of the free dication BEs due to the Madelung potential of the ionic oxides. The trend given by the sum of these two contributions to the chemical shifts is in full agreement with experiment. These mechanisms are electrostatic and do not involve chemical bonding effects.

Binding energies and chemical shifts of least bound core electron excitations in cubic ANB8−N semiconductors

AbstractCore electron binding energies EB with respect to the vacuum level and their chemical shifts are calculated for the least bound core levels of cations and anions of cubic ANB8−N semiconductors. Starting from the HF‐binding energy of the free atom absolute values of EB are obtained by adding core level shifts and relaxation energies. Core level shifts are calculated by means of an electro‐static model with ionic and bond charges according to Phillips' bond charge model. For the calculation of relaxation energies the linear dielectric theory of electronic polarization is applied. Valence and core electrons, and diagonal and non‐diagonal screening are taken into account. The theoretical results for chemical shifts of binding energies are compared with experimental values from XPS‐measurements corrected by work function data. Good agreement is obtained in all cases within the error limit of about one eV. Chemical and atomic trends of core level shifts, relaxation energies, and binding energies are discussed in terms of changes of atomic and solid state parameters. Chemical shifts and relaxation energies are predicted for various ternary ANB8−N compounds.

Transition Potential Models for Auger Electron Spectra

Three models for predicting chemical shifts of Auger electron lines are presented. A relation between binding energy chemical shifts and Auger shifts is deduced. The difference in relaxation energy between the Auger and ordinary photoionization process is explicitly included in the analysis. Ambiguities in the use of equivalent cores potential models are pointed out and removed. Computational schemes are proposed and illustrated.

Note on the correlation of the K-shell electron binding energy chemical shifts with NMR chemical shifts

The correlation of K-shell electron binding energy chemical shifts, Δ E b(ν), with NMR chemical shifts, δ ν, is investigated for some halomethanes for ν = 13C and F.

On the interpretation of k-shell electron binding energy chemical shifts in molecules

The relationship between the potential-at-a-point and orbital energy difference methods of computing K-shell electron binding energy chemical shifts, and their affinity to the nuclear shielding effect in NMR spectroscopy is demonstrated.