Core Level Binding Energy Shifts Research Articles

Core-level binding energy shifts in dilute alloys

Core level binding energy shifts for the element A of a large number of dilute alloys A B have been measured, where the concentration of the dilute component A is 10% or less. The experimental shifts are analysed in terms of alloy heat of formation data, for which we have used Miedema's semi-empirical scheme. Good overall agreement is obtained between the experimental data and the calculated values, encouraging the use of electron spectroscopy for evaluating solution energies of metallic systems.

Thermochemical analysis of Pd xAg 1- x alloys from XPS core-level binding energy shifts

XPS core level binding energy shifts of the 3d 5 2 energy levels of Pd and Ag for a large number of coevaporated Pd x Ag 1- x alloys with 0⩽ x⩽1 have been measured. An analysis of the Pd level shifts yields the heats of formation of the PdAg alloy system in good agreement with those reported from calorimetric measurements. Combining these data with the Ag level shifts one obtains the heat of formation of Cd diluted into Pd x Ag 1- x .

Calculated transition-metal surface core-level binding-energy shifts

Calculated transition-metal surface core-level binding-energy shifts

Surface Core-Level Binding-Energy Shifts for GaAs(110) and GaSb(110)

Surface $3d$ and $4d$ core-level binding-energy shifts have been resolved in photoemission from GaAs(110) and GaSb(110), which yield new information on semiconductor surface reconstruction. The shifts (\ensuremath{\sim}0.3 eV) are toward higher (lower) binding energies for the surface cations (anions), in agreement with a simple model involving the known surface relaxation of GaAs(110) with a geometry-dependent initial-state charge transfer. Surface core-excitation binding energies, core-level widths, escape depths, etc., are reevaluated.

Core-level binding-energy shifts for the metallic elements

A general treatment of core-level binding-energy shifts in metals relative to the free atom is introduced and applied to all elemental metals in the Periodic Table. The crucial ingredients of the theoretical description are (a) the assumption of a fully screened final state in the metallic case and (b) the ($Z+1$) approximation for the screening valence charge distribution around the core-ionized site. This core-ionized site is, furthermore, treated as an impurity in an otherwise perfect metal. The combination of the complete screening picture and the ($Z+1$) approximation makes it possible to introduce a Born-Haber cycle which connects the initial state with the final state of the core-ionization process. From this cycle it becomes evident that the main contributions to the core-level shift are the cohesive energy difference between the ($Z+1$) and $Z$ metal and an appropriate ionization energy of the ($Z+1$) atom (usually the first ionization potential). The appearance of the ionization potential in the shift originates from the assumption of a charge-neutral final state, while the contribution from the cohesive energies essentially describes the change of bonding properties between the initial and final state of the site. The calculated shifts show very good agreement with available experimental values (at present, for 19 elements). For the other elements we have made an effort to combine experimental ionization potentials with theoretical calculations in order to obtain accurate estimates of some of the atomic-core-level binding energies. Such energies together with measured metallic binding energies give pseudoexperimental shifts for many elements. Our calculated core-level shifts agree exceedingly well also with these data. For some of the transition elements the core-level shift shows a deviating behavior in comparison with that of neighboring elements. This is shown to be due to a difference in the atomic ground-state configuration, such as, for example, ${d}^{5}s$ in chromium relative to the ${d}^{n}{s}^{2}$ configuration in vanadium and manganese. When the core-level shift is referred to, the ${d}^{n}{s}^{2}$ (or ${d}^{n+1}s$) atomic configuration for all the elements in a transition series, a quite regular behavior of the shift is found. However, some structure can still be observed originating from a change of screening within the $d$ band from a bonding to an antibonding type as one proceeds through the series. For elements beyond the coin metals the screening of a core hole is performed by $p$ electrons, which provide a less effective screening mechanism than the $d$ electrons for the transition metals. The coin metals are intermediate cases, partly due to a dominating $s$-electron screening and partly due to $d$-electron bonding in the initial state. The effect of the electron-density redistribution between the free atom and the solid on the core-level shift is particularly striking in the case of the rare-earth elements Pr-Sm and Tb-Tm. Here the remarkable situation is that a deep core electron is less bound in the atom than in the solid. Also for the actinides the electronic redistribution upon condensation gives rise to pronounced effects on the core-level shifts. Further, it is shown that the measured $6{p}_{\frac{3}{2}}$ binding energy in metallic uranium provides a clear demonstration of the occupation of the $5f$ level in this metal. The present treatment of the core-level shift for bulk metallic atoms can easily be generalized to surface atoms. From an empirical relation for the surface energy a simple expression for the shift of the surface core-level relative to the bulk can be derived. For the earlier transition metals, it is found that the core electrons are more bound at the surface than in the bulk, while for the heavier ones the opposite situation exists. This change of sign of the surface shift depends on the bonding-antibonding division of the $d$ band. To illustrate how the present approach can be applied to alloy systems, a treatment of core-level shifts for rare-gas atoms implanted in noble metals is undertaken.

Core level binding energy shifts between free and condensed atoms

Assuming a fully screened final state (in the metallic case) and using the ( Z + 1) approximation and a Born—Haber cycle we calculate the shift in the core level binding energy between the free atom and its metallic state. The agreement with known experimental shifts is shown to be very good. Utilization of the present method can for example give accurate core level binding energies for those free atoms where such data only exist for the metallic phase.

Core-Level Binding-Energy Shifts in Metals

We describe a theory of core-level binding-energy shifts in metals (relative to the free atom). Precise definitions of the intuitive concepts of chemical, relaxation, and configuration shifts are given which permit their straightforward and unambiguous evaluation. Parameter-free calculations for the $3d$ transition series agree well with experiment. The simplicity of the theory should make it widely applicable.

X-ray photoemission studies of tellurium and some of its compounds

The energies of the 3p1/2,3/2, 3d3/5,5/2, 4s, and 4d3/2,5/2 photopeaks have been measured for tellurium metal and 23 of its compounds. An attempt is made to interpret chemical bonding in some of the tellurium compounds by comparing core level binding energy shifts with isomer shifts observed through Mossbauer spectroscopy. The widths of the 3p3/2 photopeaks measured relative to the 3p1/2 photopeaks are examined for broadening by electric field gradients and Coster–Kronig transitions. Variations in the spin–orbit splitting of the tellurium 4d level in its various compounds do not seem to be dependent on crystal field interactions.

ChemInform Abstract: THE RELATION OF CORE-LEVEL BINDING ENERGY SHIFTS TO PROTON AFFINITY AND LEWIS BASICITY

Chemischer InformationsdienstVolume 5, Issue 44 Article ChemInform Abstract: THE RELATION OF CORE-LEVEL BINDING ENERGY SHIFTS TO PROTON AFFINITY AND LEWIS BASICITY R. L. MARTIN, R. L. MARTINSearch for more papers by this authorD. A. SHIRLEY, D. A. SHIRLEYSearch for more papers by this author R. L. MARTIN, R. L. MARTINSearch for more papers by this authorD. A. SHIRLEY, D. A. SHIRLEYSearch for more papers by this author First published: November 5, 1974 https://doi.org/10.1002/chin.197444098Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume5, Issue44November 5, 1974 RelatedInformation

Relation of core-level binding energy shifts to proton affinity and Lewis basicity

Gas-phase oxygen 1s binding energy shifts, ..delta..E/sub B/(O 1s), in simple aliphatic alcohols were found to decrease in the order: water > methyl > ethyl > isopropyl > teri-butyl. Comparison with potential-model calculations showed that the shifts are attributable to relaxation in the molecular ion final state (polarization effects) rather than to the initial-state charge distribution (inductive effects). The ability of methyl groups to stabilize charge in the ion is consistent with the observation of Brauman and Blair that the gas-phase acidity order is tert-butyl >...> H/sub 2/O. It was predicted that ..delta..E/sub B/(O 1s) approx. -..delta..(proton affinity) for these compounds. In fact the agreement between these two parameters is excellent; thus ..delta..E/sub b/(O 1s) appears to measure relative Bronsted basicities; the ..delta..E/sub B/(O 1s)vs. -(PA) relation may also be applicable to substituted alcohols (the CF/sub 3/CH/sub 2/OH point agrees very well with the above alcohols) and possibly to other functional groups. The N(1s) binding energy, which decreases in the order NH/sub 3/ > CH/sub 3/NH/sub 2/ > (CH/sub 3/)/sub 2/NH > (CH/sub 3/)/sub 2/N, shows excellent agreement with -..delta..(PA) in these compounds. The calculated relaxation-energy (or polarization) contribution to ..delta..E/sub B/ for both alcohols and amines agrees very wellmore » with the variation in the lone-pair ionization potential, thus giving quantitative support to a suggestion made by Price in 1947. The ..delta..E/sub B/ values for core electrons can be regarded as measuring Lewis basicity if the latter is extended to include nonbonding core orbitals. Thus I(3d/sub 5/2/) shifts in alkyl iodides are in excellent agreement with the O(1s) shifts in alcohols, with tert-butyl iodide being a stronger Lewis base than methyl iodide.« less

Core-level binding-energy shifts in small molecules

Binding-energy shifts of carbon and fluorine 1s levels in small (two to four carbon) fluorinated hydrocarbons are reported. Carbon, nitrogen, and oxygen 1s shifts for a number of other molecules are also reported. All samples were studied as gases: A total of 72 new shifts were measured. The results are analyzed using three electrostatic potential models. First the RPM theory, which includes final-state relaxation, was used. It correctly predicts the N(1s) shifts in methylamines, for which relaxation shifts are dominant, showing the importance of considering relaxation when comparing unlike molecules. The GPM theory involves only ground-state properties. It gives excellent results for carbon, oxygen, and fluorine shifts if only groups of similar molecules are compared. Finally, atomic charges are derived using the ACHARGE model. These charges agree very well with CNDO/2 charges. The ``charge alternation'' effect deduced in CNDO/2 calculations was observed— substitution of F for H on a carbon atom decreases the charge on the next carbon by about 0.025e in ethane, 0.045e in benzene, and 0.06e in ethylene, according to the ACHARGE analysis. Inductive charge transfer was found to be additive.

The prediction of core-level binding-energy shifts from CNDO molecular orbitals

Abstract A theory is described for calculating core-level binding-energy shifts with potential models that employ “intermediate-level” molecular-orbital wave functions. The relaxation-energy term in atomic core-level binding energies is considered first. The ground-state potential model (GPM) and relaxation-potential model (RPM) are developed for calculating core-level binding energy shifts in molecules from CNDO wavefunctions. It is shown that neglect of certain two- and three-center integrals in these models limits their accuracy when unlike molecules are compared. The models are modified by calculating r−1 integrals, to be sensitive to bond directions of p orbitals. The pp′ modification, in which a subset of the neglected integrals is retained to recover invariance to coordinate transformations, is thereby necessitated. The GPM approach yields shifts in very good agreement with experiment when comparisons are restricted to similar molecules. The RPM version gives better agreement especially over wider classes of molecules. It also provides relaxation energies VR that can be combined with ab initio orbital energies to give binding energies. Several applications of these potential models are discussed.

Core-level binding energy shifts and the average quantum mechanical potential at a nucleus from CNDO [complete neglect of differential overlap] theory

Core-level binding energy shifts and the average quantum mechanical potential at a nucleus from CNDO [complete neglect of differential overlap] theory

A relaxation correction to core-level binding-energy shifts in small molecules

A theoretical method for correcting core-level binding-energy shifts for final-state relaxation effects in the framework of the CNDO model is derived a binding energies in gaseous molecules.

Near equivalence of the quantum mechanical potential model and the thermochemical model of ESCA shifts

Jolly's thermochemical model of core-level binding energy shifts is shown to depend on the same approximation that was made by Schwartz in deriving the potential model. Several implications for the calculation of these shifts are pointed out.

Comparison of Core-Level Binding Energy Shifts in Molecules with Predictions Based on Koopmans' Theorem

Comparison of Core-Level Binding Energy Shifts in Molecules with Predictions Based on Koopmans' Theorem