KLL auger and core level (1s and 2p) photoelectron shifts in a series of gaseous sulfur compounds

Core (1s and 2p) X-ray photoelectron shifts and KLL (¹D₂) Auger shifts for 22 sulfur compounds have been measured. The values have been correlated by means of atomic charge plus remote potential or central atom potential models. Either approach is equally effective tor binding energy correlations. The relaxation corrected and transition state models are in general superior to ground state models. Auger shift predictions are however poor in all cases. Absolute total static relaxation and extra-atomic relaxation values have been assessed by using the Auger parameter of Lang and Williams and relativistic atomic calculations for the free atom and its ions. These extra-atomic relaxation components are not additive but rather obey an average contribution behavior. The relaxation shift values have been compared with those obtained from the original Auger parameter (α) of Wagner. The correlation of 1s and 2p binding energies suggested a revised relationship for the Wagner Auger parameter and an equivalent simple form of the Lang and Williams parameter which can be used with satisfactory results when only the usual experimental binding energy (2p) is available in conjunction with the Auger shift.     

Origin of XPS binding energy shifts in Ni clusters and atoms on rutile TiO2 surfaces

Cluster-size-dependent binding energy (BE) shifts of Ni 2p_3/2 spectra in Ni clusters with respect to bulk Ni metal have been studied as a function of Ni coverage on clean rutile TiO₂(0 0 1) and TiO₂(1 1 0) surfaces at room temperature. As a common method to distinguish initial and final state contributions to the core-level binding energy shifts in clusters, Auger parameter (AP) analysis of photoelectron spectra has been employed and reveals an obvious initial state contribution at the coverage of 0.5 monolayers (ML). From a comparison of results for TiO₂(0 0 1) and (1 1 0) surfaces, the initial state effect is demonstrated to be strongly affected by the substrate and is assigned to a combination of eigenvalue shift in surface core-level shift (SCLS) and charge transfer between the metal clusters and substrates. The Ni 2p_3/2 BE’s of atomic Ni on TiO₂(0 0 1) and (1 1 0) surfaces are deduced to be 853.69 and 853.55 eV, respectively, from an extrapolation of the experimental BE curves to zero Ni coverage. Compared with atomic Ni in gas phase, relaxation shifts of 7.34 and 7.48 eV are obtained on TiO₂(0 0 1) and (1 1 0) surfaces, respectively. These values are very close to the relaxation shift of 7.3 eV due to d electron screening, indicating d-like screening effects from the TiO₂ substrates after Ni 2p photoionization.     

Gas phase and solid state X-ray photoelectron spectra of the substituted acetylenes (SF5)n C2 (CF3)2−n (n = 0, 1, 2): A comparison of the pentafluorosulfur and trifluoromethyl groups

The core level X-ray photoelectron spectra (XPS) of CF₃CCCF₃, CF₃CCSF₅ and SF₅CCSF₅ have been measured in the solid state. Gas phase spectra of CF₃CCCF₃ and CF₃CCSF₅ have also been obtained. The XPS data, interpreted with the point charge potential model and semiempirical MNDO (minimum neglect of differential overlap) molecular orbital calculations, indicate that the electron withdrawing effect of the ?CF₃ group is greater than that of the ?SF₅ group. Results further suggest that sulfur 3d orbitals do not play a detectable role in the bonding or charge distribution in these molecules. Carbon 1s linewidths of ?CF₃ carbon atoms are found to be much narrower than those arising from the acetylenic carbon atoms. The narrower lines correlate with the much higher binding energy of the ?CF₃ carbon atoms. Large shifts (nearly 1 eV) in heteroatom core level binding energy differences (for example, F 1s — C 1s) between the gas phase and solid state data are observed. These shifts are attributed to solid state effects (Madelung potential, intermolecular bonding interactions, and/or extramolecular relaxation contributions). From these comparisons it is clear that solid state effects are not uniform in their influence on the photoionized sites in these molecules.     

Structure relations in the x-ray photoelectron spectra of three chromium compounds

The chemical shift in electron binding energy, magnetic splitting of electron shells, and structures in the valence band are examined for chromium in the 3 + and 6 + oxidation states.The splitting of the Cr 3s energy level is associated with the appearance of a sharp Cr 3d line in the valence band. The relative chemical shift in the Cr 2p_{$\text{3}\text{2}$} line between Cr₂O₃ and K₂Cr₂O₇ is verified in the mixed compound KCr₃O₈ which contains both types of Cr ions, and the structure of this compound is verified by the X-ray photoelectron spectra. The spin-orbit intensity ratio of the 2p doublet of Cr⁶⁺ is 3, instead of the theoretical value of 2, and the spin-orbit splitting is less than for Cr³⁺. In the 3p level of Cr the relative chemical shift is 3.5 eV whereas for the 2p_{$\text{3}\text{2}$} level the shift is only 2.4 eV. The differences in chemical shift and intensity ratio can not be explained.     

Solid-state shifts in the L3M4,5M4,5 Auger spectra of the elements Cu TO Se

The kinetic-energy shifts between atomic and solid-state L₃M_4,5M_4,5 Auger electron spectra of Cu, Zn, Ga, Ge, As, and Se are determined with the aid of semiempirically calculated atomic and experimental solid-state Auger energies. The shift values are calculated by applying the thermochemical model to the Auger process. Good agreement is found between the calculated and experimental values.     

An enthalpy of solution of chromium in iron studied with Fe Mössbauer spectroscopy

The room temperature Mössbauer spectra of ⁵⁷Fe were measured for iron-based solid solutions Fe_1−xCr_x with x in the range 0.01≤x≤0.05. The obtained data were analysed in terms of the binding energy E_b between two chromium atoms in the studied materials using the extended Hrynkiewicz–Królas idea. It was found that the energy is positive or Cr atoms interact repulsively. The extrapolated value of E_b for x=0 was used for computation of an enthalpy of solution of Cr in Fe. The result was compared with corresponding data derived from calorimetric measurements and resulting from the cellular atomic model of alloys by Miedema as well as with the proper values given in the literature which were calculated on the basis of density functional theory (DFT). The comparison shows that our findings are in good agreement with the recent DFT computations for ferromagnetic Fe–Cr alloys.     

Two hole spectra and valence states in chromium and chromium silicides

Auger spectra for L₃M₂₃V and L₃V V transitions involving, respectively, one and two valence holes in the final state, have been measured for Cr and CrSi₂ using both X-ray photons and electrons as ionization source. Careful subtraction of the energy losses from the raw data permits determination of the lineshape of the Auger spectra. The valence hole spectral functions derived from the L₃M₂₃V transitions are compared with valence band spectra obtained by X-ray photoemission. The comparison provides direct evidence of the importance of multiplet coupling between the 3p and 3d holes in the final state. Results for the spectral function of two valence holes are consistent with the outcome of band structure calculations, although some correlation effects seem to be present.     

The ultraviolet spectrum of SO2 in matrix isolation and the vibrational structure of the 2348 Å system

The absorption spectra of SO₂ in solid neon and argon have been observed in the spectral regions near 2200 Å and 2900 Å. The spectral shifts of the electronic transitions in the matrix relative to the vapor are reported, including a shift with aging of the matrix. Implications for the interpretation of the vibrational structure of the 2348 Å system are discussed. A large spectral shift is attributed to a shift of the vibrational frequency 2ν₃′ of the excited electronic state.     

Isotope shifts of the ground state of neon: Refining the measurement results

Abstract—It has been revealed that the published results of measurements of the isotope shift of the ground state of even neon isotopes contain systematic errors. The errors are caused by the use of erroneous data regarding the absolute values of specific mass shifts of excited states and by the measurement errors of the isotope shifts themselves for transitions to the ground state. The isotope shift of the 2p⁵4s[3/2]₁ → 2p⁶(¹S₀) transition has been measured to be 2305 ± 20 MHz, the absolute specific mass shift of the 3p[3/2]₂: (2_р9) level has been determined to be 647 ± 10 MHz, and the isotope shift of the ground state has been found to be–3156 ± 30 MHz.     

Accurate core binding energies of ions from Dirac-Fock calculations combined with experimental atomic binding energies

Core binding energies are reported for the singly-charged alkali ions obtained by removing the outer s electron and for the singly-charged halide ions obtained by adding a P_{$\text{3}\text{2}$} electron. The levels studied are Li 1s, Na 1s, K 2p, Rb 3p, Cs 3d, F 1s, Cl 2p, Br 3p and I 3d. The binding energies were obtained by combining DiracF?ock ΔSCF binding-energy shifts between the ions and the corresponding isoelectronic rare gases with experimental rare-gas binding energies, and also by combining the calculated atomīon shifts with experimental atomic binding energies where available. It is shown that the former approach corrects accurately for the correlation energy, which is not included in single-configuration calculations.     

State-specific,many-electron theory of core levels in metals: The 1s binding energy of Be metal

Cluster ΔSCF theory is combined with calculations of atomic electron correlation to predict the 1s binding energy of Be metal as 115.4 eV, in excellent agreement with experiment (115.2–115.6 eV). Upon creation of the 1s hole, the p character of the valence band increases significantly. This explains the existing discrepancy between the experimental solid state fluorescence yield of Be and the theoretical prediction for the atomic state.     

Kα X-ray satellite spectra of Ti, V, Cr and Mn induced by photons

K X-ray emission spectra of Ti, V, Cr and Mn generated by photon excitation have been studied with a crystal spectrometer. The measured energy shifts of K_α satellite relative to the diagram line are compared with values obtained by electron excitation and with different theoretical estimates. The present experimental values of K_αL¹/K_αL⁰ relative intensities are compared with values obtained by electron excitation.      

Determination of effective atomic charge,extra-atomic relaxation and madelung energy in chemical compounds on the basis of X-ray photoelectron and auger transition energies

A new method is proposed for the determination of effective atomic charge, extra-atomic relaxation, and Madelung energy in chemical compounds, based on the experimentally measured energies of X-ray photoelectron and Auger transitions. The method has been applied to solid compounds of the elements from Na to Cl, and to a number of free sulfur-, phosphorus-, silicon-, and chlorine-containing molecules. The experimental energies are represented as consisting of two parts. The first part is determined by the ionization energy of a free ion with a given effective charge, and includes the intra-atomic relaxation. The second part is determined by the Madelung energy and the extra-atomic relaxation. The first contribution is calculated by using the Hartree-Fock method. The effective atomic charges required have been found from the shifts of Kα-lines in the X-ray spectra. The extra-atomic relaxations are obtained as the differences between experimental and theoretical Auger parameters, and the values calculated are the additive functions of ligands of the atom studied. The increments of the additive scheme correlate with the ligand refractions. The effective charges, extra-atomic relaxation energies and Madelung potentials obtained from ESCA and AES data agree well with both calculated and direct experimental results.     

Binding energy shift in photoemission spectroscopy study of Ni clusters deposited on rutile TiO2 surfaces

Cluster-size-dependent binding energy (BE) shifts of Ni 2p_3/2 spectra in Ni clusters with respect to bulk Ni metal have been studied as a function of Ni coverage on clean rutile TiO₂(0 0 1) surfaces at room temperature. Auger parameter (AP) analysis of photoelectron spectra has been employed and revealed an obvious initial state contribution at the coverage of 0.5 monolayers (ML). The initial state effect was demonstrated to be strongly affected by the substrate and was assigned to a combination of eigenvalue shift in surface core-level shift (SCLS) and charge transfer between the metal clusters and substrates. The TiO₂(0 0 1) surface stoichiometry was found to introduce different charge transfer behaviors. Our results experimentally present that the Ni clusters are charged positively on stoichiomtric TiO₂ surface and less positively or even negatively on various reduced surfaces.     

The Effect of pH on solid-state 13C NMR spectra of histidine

High-resolution solid-state ¹³C NMR spectra of histidine powder samples prepared from solutions at several pH values near the pK_a of the imidazole group are presented. These spectra demonstrate several effects due to the titration of the imidazole group. The chemical shifts for all of the carbon sites change upon titration. They are in “slow exchange” in the solid state in contrast to the “fast exchange” behavior seen in solution. Changes in the quadrupole interactions in the ¹⁴N sites occur upon titration and are observed by their effects on the resonance lineshapes of the ¹³C sites to which they are bonded.     

A new charge-correction method in X-ray photoelectron spectroscopy

The 2p_{$\text{3}\text{2}$} binding energy (242.3 eV) of Ar implanted in insulating materials is available to correct for charging shifts. Argon ions hav materials SiO₂ and soda glass. In each case the charging shift for Ar 2p_{$\text{3}\text{2}$} electrons agrees exactly with those for core-level elec The charge-corrected binding energies of the insulating materials permit the identification of atomic chemical states. Ion-induced reduction of the ins investigations.     

Spectroscopic (FT‐IR,FT‐Raman,UV, 1H,and 13C NMR) and theoretical studies of m‐anisic acid and lithium,sodium, potassium,rubidium, and caesium m‐anisates

In order to understand the nature of the interactions of biologically important ligands, it is necessary to carry out the physico‐chemical studies of these compounds with their biological targets (e.g., receptors in the cell or important cell components). Results of this study make it possible to predict some properties of a molecule, such as its reactivity, durability of complex compounds, and kinship to enzymes. In this paper the effect of alkali metal cations (Li, Na, K, Rb, and Cs) on the electronic structure of m‐methoxybenzoic acid (m‐anisic acid) was studied. The experimental IR (in solid state and solution), Raman, UV (in solid state and solution), ¹H, and ¹³C NMR spectra of m‐methoxybenzoic acid, and its salts were registered, assigned, and analyzed. Some of the obtained results were compared with published data for o‐anisic acid and o‐anisates. The structures of anisic acid and Li, Na, and K m‐anisates were optimized at the B3LYP/6‐311++G** level. The IR, ¹H, and ¹³C NMR spectra and NPA, ChelpG, and MK atomic charges were calculated. The change of metal along with the series: Li → Na → K → Rb → Cs caused: (1) the change in the electronic charge distribution in anisate anion that is seen via the occurrence of the systematic shifts of several bands in the experimental and theoretical IR and Raman spectra of anisates; (2) systematic ¹H and ¹³C NMR chemical shifts; (3) hypsochromic shifts in UV spectra of salts as compared to ligands. Copyright © 2009 John Wiley & Sons, Ltd.     

Photoelectron-spectroscopic study of nickel,manganese and cobalt selenides

Photoelectron-spectroscopic studies (XPS and UPS) have been carried out to investigate electronic structure and chemical bonding in the monoselenides of nickel, manganese and cobalt. Binding-energy values and chemical shifts are reported from the XPS measurements for Ni 2p and 3s, Mn 2p and 3s, Co 2p and 3s and Se 3p and 3d. The electronic structure and bonding in the monoselenides are interpreted from an analysis of the valence-band spectra. The combined XPS and UPS data suggest transfer of electrons from the metal orbitals (Ni, Mn and Co) to selenium, contrary to bonding schemes proposed previously in the literature. Magnetic-susceptibility measurements performed by us indicate NiSe to be diamagnetic and MnSe and CoSe to be highly paramagnetic at room temperature. The presence of shake-up satellites in the XPS spectra for MnSe and CoSe and their absence for NiSe are discussed in relation to these magnetic properties.     

Pi-mesic decays of A = 4 hypernuclei

Angular distributions and energy spectra for the decay modes _Λ⁴He→π^?p³He, _Λ⁴H → π^?p³H, _Λ⁴H → π^?n³He are calculated and compared with experiment. Final state nuclear interactions have been adjusted to fit the corresponding scattering data. With S-, P- and D-wave interactions we were able to obtain reasonably good agreement with the experimental decay spectra. It is suggested that the _Λ⁴H → π^?n³He decay spectra may be decisive in selecting the right set of p³H complex phase shifts from several possible solutions.     

Hyperfine structure in the 6p5d configuration and isotope shifts in transitions between the 6s5d and the 6p5d configurations in Ba I

High-resolution laser fluorescence spectroscopy, using a single-mode dye laser acting on a collimated atomic beam, has been performed to determine the hyperfine-structure (hfs) constants in six states of the 6p 5d configuration of¹³⁵Ba and¹³⁷Ba. Isotope shifts (IS) for eleven transitions between the 6s 5d and the 6p 5d configurations have also been measured. From an analysis of the energy levels, intermediate angular wavefunctions have been deduced. The wavefunctions are used to evaluate experimental hyperfine parameters from the experimental hfs constants. The parameters are, for the magnetic-dipole interaction compared with theoretical values, and for the electricquadrupole interaction used to estimate the nuclear quadrupole moments for the odd isotopes. The IS in the measured transitions are analysed using a King-plot, with the first resonance line in Ba II as the reference. Specific mass and field shifts are evaluated for the measured transitions. The field shifts have been used to determine the change in mean-square radius between the natural abundant Ba-isotopes.