Theoretical Fine Spectroscopy with SAC-CI Method: Outer- and Inner-Valence Ionization Spectra of CO and N2

Abstract

Outer- and inner-valence ionization spectra of CO and N2 were studied by the SAC-CI (symmetry-adapted-cluster configuration-interaction) general-R method. Fine details of experimental spectra of these molecules were reproduced and quantitative assignments of the peaks were proposed. Both outer- and inner-valence satellites were classified into the shake-up states including the valence or Rydberg excitations. For CO, theoretical satellite spectrum up to 50 eV was presented and the nine bands of 22-50 eV observed by EMS and eight bands of 22-34 eV by XPS (C-K) were characterized in detail. Numerous satellite peaks with distributed intensity were obtained and some of them, especially for bands 4, 5, 6 and 7, were predominantly described by triple-electron processes. For N2, the spectrum up to 45 eV was calculated and the complex satellite peaks observed by XPS in the lower energy region 20-33 eV were interpreted. The detailed assignments for the (2σg-1) satellite states in the higher-energy region 33-45 eV were also presented.