G. Johansson

Molecular Spectroscopy by Means of ESCA II. Sulfur compounds. Correlation of electron binding energy with structure

Electron spectra from an extensive series of sulfur compounds have been studied. A correlation has been established between the observed position of inner electron lines of sulfur and structure. The influence of structure on the electron binding energies is discussed in terms of a calculated atomic charge, based on the concepts of electronegativity and partial ionic character of bonds. The results are useful for the study of bonding and structure in sulfur chemistry, and are applied particularly to the discussion of the sulfur-oxygen bond (S=O).

Charge transfer in transition metal carbides and related compounds studied by ESCA

Abstract Electron spectroscopic measurements of binding energy shifts of Cl s electrons in Group 4 b , 5 b and 6 b carbides and of core electrons in Ti and V compounds are presented. The results are discussed and compared with X-ray spectroscopic investigations and energy band calculations. It is shown that electrons are transferred from the metal to the carbon atoms when a carbide of this type is formed.

Calibration of electron spectra

Abstract Energy calibration procedures, which have been used in ESCA, are reviewed. Binding energies of calibration lines suitable for solid and for gaseous samples have been determined. Charging effects of nonconducting samples have been investigated for different X-radiation, sample thickness and material. A calibration relative to lines from some insulating standard compound mixed into the sample was shown to be unreliable, while experiments indicated that in calibrating relative to a surface layer, the carbon line from the hydrocarbon contamination layer can be used as well as a line from a thick layer of a noble metal on a part of the sample.

The ESCA Spectra of Benzene and the Iso-electronic Series, Thiophene, Pyrrole and Furan

The ESCA spectra of C6H6, C4H4S, C4H5N and C4H4O have been studied using MgKα radiation, 1253.6 eV. The study included both the core orbitals and the valence orbitals. The C1s chemical shifts have been compared with the shifts predicted by the potential model, using both CNDO and ab initio gross atomic charges. We have obtained the binding energies of the deeper lying valence orbitals which cannot be reached by ultraviolet radiation. Further, the valence orbital spectra have been analysed using line intensities predicted from the atomic population of the molecular orbitals.

Valence Bands and Core Levels of the Isoelectronic Series LiF, BeO, BN, and Graphite Studied by ESCA

The core lines and valence bands of LiF, BeO, BN and graphite have been studied by the ESCA technique. The energy differences between inner levels and valence bands are compared with X-ray transition energies. The changes in binding energy for the Bels level when going from metal to oxide and fluoride are compared with X-ray spectroscopic data and with a study of the disintegration constant in electron capture of 7Be in the same compounds.

ESCA studies of CO2, CS2 and COS

Abstract The core level electron spectra of CO 2 , CS 2 and COS excited by Mg Kα radiation have been studied to identify shake-up satellite lines associated with ionization from these levels. A number of such lines have been seen and possible assignments have been suggested using the excited states of the molecule as a guide. The valence spectra have also been recorded and they too were found to be rich in shake-up structure. The observed variation of the valence line intensities is discussed and compared with predictions made from an intensity model. The validity of distinguishing between π and σ symmetries in linear molecules in applying the intensity model is confirmed.

VC, NbC and TaC with varying carbon content studied by ESCA☆

Abstract Electron spectroscopic studies by the ESCA technique of core level electrons in VC, NbC and TaC with varying carbon contents show that the electron transfer from the metal atoms increases with increasing carbon content in the VC phase but decreases in the NbC and TaC phases. The VC phase resembles the TiC phase measured in a previous investigation. The ESCA shifts are compared with heats of formation.

Ionization energies in methane and ethane measured by means of ESCA

Abstract Ionization energies for the molecular orbitals in methane and ethane are obtained by means of the ESCA technique. In methane the 2a 1 electrons are found at a binding energy of 23.1 eV; in ethane the 2a 1 level is split up in two levels due to the interaction between the carbon atoms.

The KLL Auger spectrum of fluorine

The KLL Auger spectrum of fluorine (Z=9) has been studied in three different fluoride salts. Five Auger lines are observed in each compound in accordance with extreme LS coupling theory. A cation dependence of the Auger transition energies and line-widths is observed. The energy shifts are in agreement with a theoretical model.

Chemical shifts in ESCA and NMR

Abstract A detailed examination of the relationship between chemical shifts in ESCA and NMR is presented. It is demonstrated that even in series of closely related compounds a linear correlation between ESCA and NMR shifts cannot be expected. Included is a discussion of reorganization effects on electron binding energies. The close relation between chemical shifts of ESCA and NMR and the spin—rotation constants of molecules is pointed out.