Calculation of the inner shell excitation spectra and estimation of the electron scattering and dissociative attachment resonance energies of SF 6, SO 2, SF 2O, SF 2O 2, SF 4, SF 4O and S 2F 10

Abstract

We have calculated the S inner shell excitation spectra of SF 6, SO 2, SF 2O, SF 2O 2, SF 4, SF 4O and S 2F 10 using ab initio methods within the equivalent ionic core virtual orbital model. For SF 4 we have taken energy differences between initial and final states of the core excited molecules at both the SCF and SCF-CI levels, while for the other molecules we have used only a Koopmans' theorem level approach. Trends in inner shell spectral energies for the whole series of molecules are adequately reproduced at the Koopmans' theorem level and quantitative agreement with experiment is obtained for SF 4 at the Δ E SCF-CI level. Direct SCF calculations of the vertical electron affinities of the neutral molecules SO 2, SF 4 and SF 2O 2 allow us to evaluate a stabilization energy, connecting the term energy of a given unoccupied orbital in inner shell excitation spectra and the energy of the cross-section maximum it produces in electron scattering or dissociative electron attachment. Using this stabilization energy plus experimental inner shell term energies we can correctly reproduce trends in the energies of dissociative electron attachment within this series. For SF 4 and SF 2O 2 we have also calculated both inner shell spectral intensities (within the dipole approximation) and orbital electron density plots to more fully characterize the empty orbitals. The lowest energy empty orbital of core ionized SF 2O 2 is both SO π* and SF σ* in character and is consequently less stable than the LUMO of SF 4 which has onlySF σ* character.