A vibrationally resolved experimental study of the sulfur L-shell photoelectron spectrum of the CS2molecule

The sulfur L-shell photoelectron spectrum of the carbon disulfide molecule has been studied using monochromated synchrotron radiation with a photon energy of 250 eV. The spectrum is atomic like, showing three major bands that can be associated with the sulfur (2p -1 ) 2 P 3/2,12 and (2s -1 ) 2 S 1/2 ionic states. A closer inspection shows that the 2 P 3/2 state is further split into two components separated by 128 meV due to the molecular field. The resulting ionic states are located at 169.806 eV (0-0 energy), 169.934 eV (0-0 energy), 171.075 eV (0-0 energy) and 237.05±0.2 eV (centroid), respectively. Vibrational progressions in the (2p -1 ) bands are attributed to the asymmetric ν 3 mode, which gives evidence of a localization of the core hole. The following values were obtained for the vibrational constants: ω e = 196.7±1.1 meV; ω e x e = 0.2±0.5 meV. A curve fit of the vibrational lines using a Voigt function gave a natural width of 59.6±1.8 meV for the (2p -1 ) states, corresponding to a lifetime of 11 fs, and a spectrometer broadening of 38.2±1.8 meV. The (2p -1 ) bands are accompanied by shake-up structures occurring at 6-18 eV higher energies. They are interpreted mainly in terms of excitations to the unoccupied 3π u * orbital in the final ionic state. The (2s -1 ) 2 S 1/2 band is broad and structureless due to fast Coster-Kronig processes. A fitting of a Voigt function gives a natural line-width of 1.85 eV which corresponds to a lifetime of 0.4 fs.