An ESCA study of the molecular core binding energies of the chlorobenzenes

The carbon 1s and the chlorine 2s and 2p molecular core binding energies of the complete series of chlorobenzenes have been measured. The assignments of the C 1s binding energies are discussed in terms of CNDO/2 SCF MO calculations and the effect of including and excluding d orbitals in the basis set for chlorine is investigated. The measured binding energies have been used to calculate experimental charge distributions within the molecules.     

A study of atomic iodine and molecular thallium iodide by X-ray photoelectron and auger electron spectroscopy

The I3d5/2 binding energy has been measured in atomic iodine, thallium iodide and cesium iodide by high temperature gas-phase photoelectron spectrscopy using Al K (1486.6 eV) X-rays. The iodine M₅N_4,5N_4,5 (¹G₄) Auger energies for TlI and CsI have also been measured and combined with binding energies to yield extra-atomic relaxation energies of 0.5 and O.3 eV, respectively, after corrections are applied to the Auger parameter. Charges were calculated using the simple potential model, which was also used to obtain an estimate of the atomic T14f binding energy. Two other estimates of the atomic T14f7/2 binding energy have also been calculated, both based on Dirac-Fock ΔSCF binding energies. The results of the three methods suggest a value of 125.3 ± 0.2 eV for T14f7/2.     

Resonant shake-up satellites in photoemission at the Ga 3p photothreshold in GaN

Photoemission spectra recorded near the Ga 3p photothreshold from GaN have been found to contain satellites of the main Ga 3d emission line. The intensity of these satellites resonate at this threshold, and are associated with a 3d⁸ state. The correlation energies and binding energies for the satellite multiplet have been measured for the satellite and related Auger transitions. The satellite multiplet contains additional constant binding energy features not observed in previous studies of other Ga compounds. The present results are compared with those for GaP and GaAs.     

An ESCA study of organosilicon compounds

The silicon 2p electron binding energies have been measured for a series of 33 organosilicon compounds. The binding energies are correlated with partial atomic charges calculated by various electronegativity models and CNDO calculations. Group shifts are reported for various chemical groups attached to silicon and are found to correlate with group shifts reported for carbon and phosphorus compounds.     

Molecular spectroscopy by means of ESCA: V. Boron compounds

The B 1s binding energies of 23 compounds, including boron hydrides and carboranes have been measured in the vapor state. Correlations with Pauling charges and with shifts, calculated from the potential model using CNDO charges, are presented. The B 1s binding energies are subsequently discussed in terms of the chemical reactivity of the compounds. The iodomethanes have also been studied, and an electronegativity value for iodine suitable for ESCA correlations is given.     

Adsorption of single alkali atoms on tungsten using field emission and field desorption

Single adatom events have been detected and the binding energies and dipole moments of single sodium, potassium and cesium adatoms have been measured on the (110), (112) and (111) planes of tungsten in a probe hole field emission microscope. The Fowler-Nordheim formulation has been modified to include averaging effects implicit in probe hole measurements on single adsorbed atoms. The work function changes and consequent dipole moments associated with single alkali adatoms on a tungsten surface have been estimated. A model has been proposed to obtain binding energies from measurements of the field required to desorb a single alkali adatom. The results are in good agreement with current theoretical predictions for the adsorption of single alkali atoms on metals.     

Esca, mössbauer and infrared spectroscopic investigations of a series of tin complexes

Core electron binding shifts have been measured for a series of tin complexes. From earlier proposed relations between binding energies, infrared intensities and the charge on the ligands we have estimated the effective charge on the tin atom. Also the isomer shifts of the central atom have been measured. By using a sample model for the interpretation of these data in terms of occupation numbers of the valence orbitals, an estimate of the electronic structure of the complexes is obtained.     

Correlation between core level chemical shifts obtained by ultrasoft x-ray emission and ESCA

High resolution C:K X-ray emission spectra have been recorded from six molecules in the gas phase. The spectra are interpreted by comparing the relative X-ray energies with the vertical ionization energies of the valence orbitals and comparing the intensities predicted by the C 2p populations from CNDO calculations with the measured intensities. The obtained C 1s binding energy shifts are found to be in excellent agreement with shifts measured with ESCA.     

Correlation between core level chemical shifts obtained by ultrasoft X-ray emission and ESCA

High resolution C:K X-ray emission spectra have been recorded from six molecules in the gas phase. The spectra are interpreted by comparing the relative X-ray energies with the vertical ionization energies of the valence orbitals and comparing the intensities predicted by the C 2p populations from CNDO calculations with the measured intensities. The obtained C 1s binding energy shifts are found to be in excellent agreement with shifts measured with ESCA.     

Photoelectron spectra of chromium tetranitrosyl

The ultraviolet and X-ray-excited photoelectron spectra of Cr(NO)₄ are reported. The electron binding energies, shake-up spectra, relative peak intensities and the Auger peak kinetic energies have been measured, and are compared to the spectra from gas-phase NO, from NO adsorbed on a transition metal surface, and to SCF-MS calculations. The theoretical calculations are utilized to obtain ionization energies and charge distributions, and consequently to discuss the bonding in nitrosyl complexes.     

Déplacement chimique ESCA dans la série des oxydes du niobium

The binding energies of the niobium levels in niobium metal and the oxides NbO, NbO₂ and Nb₂O₅, have been measured. This allows identif     

Many-body effects in the binding energies of image states at surfaces

A study of the influence of many-body effects on binding energies and effective masses of image potential induced surface states is presented. The binding energies calculated using experimentally measured ε(ω) response functions show a dependence on the electron density different from that obtained using a plasmon model, and are in agreement with recent experimental data of diesen et al. [Phys. Rev. B33 (1986) 5241]. The effects of plasmon dispersion and single particle excitations on binding energies are evaluated with a simple model, and it is shown that they result in a strong cancellation in the range of r_s values where most experimental data have been obtained (r_s ≈ 3), if realistic values of the surface plasmon dispersion relation are used. Corrections to the effective masses due to many-body effects are shown to be of the order of 1%.     

Calibration of XPS core-level binding energies: Influence of the surface chemical shift

Core-level binding energies measured in XPS are influenced by the existence of surface chemical shifts. The magnitude of this effect has been calculated for materials commonly used in the calibration of XPS instruments.     

Spectroscopy of the hypernucleus Λ12C

Kaons were stopped in a ¹²C target. The momenta of pions accompanying the kaon interactions were measured with a magnetic spectrometer. States in _Λ¹²C with binding energies of the Λ particle of 11 ± 1 MeV and 0 ± 1 MeV have been observed.     

Effects of electron screening on low-energy fusion cross sections

The effects of electron screening on the low-energy cross sections of nuclear fusion reactions of astrophysical interest have been studied within the Born-Oppenheimer approximation using a simplified model. These studies indicate that a significant enhancement of the cross sections can occur already at beam energies, which are about a factor 100 higher than the electron binding energies. Cross sections near such energies can now be measured, in some cases, and several examples are discussed. For an understanding of the low-energy data as well as for a reliable extrapolation of the cross sections (for bare nuclei) to lower energies, the effects of electron screening must be well understood.     

Self interaction corrected density functional calculation of the core level binding energies for simple metals,Mg and Al

The core level binding energies of simple metals, Mg and Al have been calculated by employing a single shot, add on self interaction correction proposed by Perdew and Norman. The correction applies to the eigenvalue of the single particle like Kohn-Sham equation. The calculations have been performed using atom in jellium model. The corrected eigenvalues show a marked improvement over the Kohn-Sham eigenvalues bringing them closed to the ΔSCF binding energies reported by Nieminen and Puska.     

Energies and chemical shifts of the sulphur 1s level and the KL2L3(1D2) Auger line in H2S,SO2 and SF6

The sulphur 1s binding energies and KL₂L₃(¹D₂) Auger energies have been measured in gaseous H₂S, SO₂ and SF₆. The experimental data, including the chemical shifts, are compared with various theoretical ab initio results. Theoretical and experimental values agree within 1-2 eV for the chemical shift and the binding energy of the 1s level, provided in the latter case relaxation, relativistic and correlation corrections are applied. Likewise, Shirley's method²⁰, which uses empirical energies, predicts the Auger energies satisfactorily. The measured S 1s binding energies are 2478.5(1) eV, 2483.7(1) eV and 2490.1(1) eV, and KL₂L₃(¹D₂) Auger energies are 2098.7(1) eV, 2095.5(2) eV, 2092.6(1) eV for H₂S, SO₂ and SF₆, respectively. The chemical shift for the 1s electron is found to be greater than for the 2s or 2p electron and in better accord with the prediction of the potential model. Data suggest the molecular relaxation energy to be small compared with the atomic relaxation energy.     

The effect of band non-parabolicity of shallow donors

We have studied theoretically the effect of non-parabolicity of conduction band on the binding energies of shallow donors. The calculation is carried out in momentum space. We find that the binding energies are increased by 3 to 5 percent for shallow donors in Hg_1-xCd_xTe, GaAs, and InP. The discrepencies between the measured donor ionization energies in GaAs and the value from hydrogenic model are, in a substantial part, due to the non-parabolicity effect.     

On the binding energies of excitons in polar quantum well structures in a weak electric field

The binding energies of excitons in quantum well structures subjected to an applied uniform electric field by taking into account the exciton longitudinal optical phonon interaction is calculated. The binding energies and corresponding Stark shifts for Ⅲ-Ⅴ and Ⅱ-Ⅵ compound semiconductor quantum well structures have been numerically computed. The results for GaAs/A1GaAs and ZnCdSe/ZnSe quantum wells are given and discussed. Theoretical results show that the exciton-phonon coupling reduces both the exciton binding energies and the Stark shifts by screening the Coulomb interaction. This effect is observable experimentally and cannot be neglected.     

X-Ray photoelectron spectroscopic study of schiff base metal complexes

Metal donor atom core electron binding energies have been measured for seven related polydentate Schifr base complexes of nickel(II) and copper(II). The potential donor atoms of all neutral ligands except one and the free metals were also studied. Rather high metal chemical shifts were observed, but no correlation between metal binding energy and known ligand field strength was noted. Satellite peaks are found in the spectra of all paramagnetic complexes.