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

Abstract

The sulfur L-shell photoelectron spectrum of the carbondisulfide molecule has been studied using monochromatedsynchrotron radiation with a photon energy of 250 eV. Thespectrum is atomic like, showing three major bands that can beassociated with the sulfur (2p-1)2P3/2,12 and (2s-1)2S1/2 ionic states. A closer inspection showsthat the 2P3/2 state is further split into twocomponents separated by 128 meV due to the molecular field. Theresulting ionic states are located at 169.806 eV (0-0energy), 169.934 eV (0-0 energy), 171.075 eV (0-0 energy) and237.05±0.2 eV (centroid), respectively. Vibrationalprogressions in the (2p-1) bands are attributed to theasymmetric ν3 mode, which gives evidence of alocalization of the core hole. The following values wereobtained for the vibrational constants: ωe = 196.7±1.1 meV; ωexe = 0.2±0.5 meV. Acurve fit of the vibrational lines using a Voigt function gavea natural width of 59.6±1.8 meV for the (2p-1)states, corresponding to a lifetime of 11 fs, and a spectrometerbroadening of 38.2±1.8 meV. The (2p-1) bands areaccompanied by shake-up structures occurring at 6-18 eV higherenergies. They are interpreted mainly in terms of excitationsto the unoccupied 3πu* orbital in the finalionic state. The (2s-1)2S1/2 band is broad andstructureless due to fast Coster-Kronig processes. A fittingof a Voigt function gives a natural line-width of1.85 eV which corresponds to a lifetime of 0.4 fs.