Valence Shell Photoelectron Spectrum Research Articles

An experimental and theoretical study of the valence shell photoelectron spectrum of sulphur hexafluoride

Abstract The complete valence shell photoelectron spectrum of sulphur dioxide has been studied using HeI, HeII and synchrotron radiation. The high resolution HeI and HeII excited spectra have allowed a detailed analysis to be made of the vibrational structure exhibited in the photoelectron bands associated with ionisation from the outer valence orbitais. A new satellite band containing vibrational structure has been observed around 19 eV. The photoelectron spectra recorded with synchrotron radiation demonstrate that the inner valence region contains several complicated structures and is dominated by a prominent feature centred at a binding energy around 34 eV. Many-body Green's function calculations have been performed to evaluate the energies and pole strengths associated with the main lines and satellite states distributed throughout the valence shell region, and an interpretation of some of the experimental features is proposed, based upon these predictions.

An experimental and theoretical study of the valence shell photoelectron spectrum of sulphur dioxide

Abstract The complete valence shell photoelectron spectrum of sulphur dioxide has been studied using HeI, HeII and synchrotron radiation. The high resolution HeI and HeII excited spectra have allowed a detailed analysis to be made of the vibrational structure exhibited in the photoelectron bands associated with ionisation from the outer valence orbitais. A new satellite band containing vibrational structure has been observed around 19 eV. The photoelectron spectra recorded with synchrotron radiation demonstrate that the inner valence region contains several complicated structures and is dominated by a prominent feature centred at a binding energy around 34 eV. Many-body Green's function calculations have been performed to evaluate the energies and pole strengths associated with the main lines and satellite states distributed throughout the valence shell region, and an interpretation of some of the experimental features is proposed, based upon these predictions.

Inner and valence shell photoelectron spectra calculated by the density functional method

Core and valence shell binding energies and core level shifts of different organic and inorganic systems have been calculated employing both the LCGTO-LSD and LCGTO-NLSD density functional-like methods. At LCGTO-NLSD level of theory the calculated C1s and O1s ionization potentials (IPs) are about 1.5 eV higher than the corresponding experimental values whereas the LCGTO-LSD computations underestimate the IP by about 2eV. The calculated chemical shifts with respect to C1s and O1s of free carbon monoxide are in good agreement with experimental evidence. In the case of the valence IPs the agreement between calculated and observed values is excellent. In all cases the addition of nonlocal corrections improve the reliability of the theoretical data.

Observation of many-body states in the valence shells of cis-, trans- and iso-dichloroethylene by synchrotron radiation photoelectron spectroscopy at 120 eV

The valence shell (8–34 eV) photoelectron spectra of cis-, trans- and iso-dichloroethylene were obtained using monochromatic synchrotron radiation at 120 eV photon energy. The spectra were compared with literature He(I) measurements and with single configuration self-consistent field calculations using three different basis sets. Although there was reasonable agreement in the ionization energies of the four outermost orbitals for all three isomers between experiment and calculation, some notable discrepancies in the energies and ambiguities in the assignments of the ionic states above 13 eV were found. Prominent many-body structures were observed in the inner valence (> 20 eV) region of these isomers for the first time. These many-body features indicate the general breakdown of Koopmans' ionization picture in this region and the need for more elaborate (configuration interaction) calculations that take account of electron correlation effects.

Photoelectron spectra of acetylene with HeI, HeII, Zr Mζ, and Mg Kα radiation sources

Valence level photoelectron spectra of gaseous acetylene excited by HeI (21.217 eV), HeII (40.8 eV), Zr Mζ (151.4 eV) with Mg Kα (1253.6 eV) radiations have been obtained. With one exception, the 3σg band under Mg Kα excitation, all of the expected valence level excitations are observed in each case. The best measured orbital ionization potentials are 1πu (11.41 eV), 3σg (16.76 eV), 2σu (18.71 eV), and 2σg (23.65 eV). All values except that for 1πu are adiabatic values. Relative photoionization probabilities (cross sections) have been determined for each of the radiations and compared to those estimated theoretically. The low calculated cross sections for 3σg excitation with Mg Kα radiation provides an explanation for the lack of an observable band due to this ionization in the photoelectron spectrum. A prominent ’’shake-up’’ peak is observed at 27.6 eV in both the Mg Kα and Zr Mζ excited valence shell photoelectron spectra although it is more pronounced in the former. Similarly the C1s core spectrum shows several ’’shake-up’’ peaks which have been assigned with the aid of CNDO calculations.

Valence orbital photoelectron spectroscopic studies of free molecules with zirconium M? soft X-ray excitation

Zirconium Mζ X-rays (151.4 eV) have been used to produce valence shell photoelectron spectra of the noble gases Ne and Ar and the molecules CH4, N2 and H2O. This radiation, which appears to be free of nearby satellites, gives good count rates and clean spectra. Since the orbitals with a large proportion of p character have a higher cross-section for photoemission with Zr Mζ than with Mg Kα, the spectra show prominent peaks for molecular orbitals with dominant p components whereas Mg Kα spectra emphasize those orbitals which have dominant s character.