A vibrationally resolved experimental study of the sulfur L-shell photoelectron spectrum of the CS2 molecule

The sulfur L-shell photoelectron spectrum of the carbon disulfide molecule has been studied using monochromated synchrotron radiation with a photon en ergy of 250 eV. The spectrum is atomic like, showing three major bands that can be associated with the sulfur (2p(-1))P-2(3/2.12) and (2s(-1))S-2(1/2) ionic states. A closer inspection shows that the P-1(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 attribute d to the asymmetric nu (3) mode, which gives evidence of a localization of the core hole. The following values were obtained for the vibrational const ants: omega (e) = 196.7 +/- 1.1 meV; omega (e)x(e) = 0.2 +/- 0.5 meV. A cur ve 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 o f 11 fs, and a spectrometer broadening of 38.2 +/- 1.8 meV. The (2p-1) band s are accompanied by shake-up structures occurring at 6-18 eV higher energi es. They are interpreted mainly in terms of excitations to the unoccupied 3 pi (*)(u) orbital in the final ionic state. The (2s(-1))S-2(1/2) band is b road 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.