Electronic Properties of FC(O)SCH<sub>2</sub>CH<sub>3</sub>. A Combined Helium(I) Photoelectron Spectroscopy and Synchrotron Radiation Study

The valence electronic properties of <i>S</i>-ethyl flouromethanethioate (<i>S</i>-ethyl fluoromethsanethioate), FC­(O)­SCH<sub>2</sub>CH<sub>3</sub>, were investigated by means of He­(I) photoelectron spectroscopy in conjunction with the analysis of the photofragmentation products determined by PEPICO (phtoelectron-photoion-coincidence) by using synchrotron radiation in the 11.1–21.6 eV photon energy range. The first band observed at 10.28 eV in the HeI photoelectron spectrum can be assigned with confidence to the ionization process from the HOMO [n<sub>π</sub>(S) orbital], which is described as a lone pair formally localized on the sulfur atom, in agreement with quantum chemical calculations using the outer valence Green function method [OVGF/6-311++G (d,p)]. One of the most important fragmentation channels also observed in the valence region corresponds to the decarbonylation process yielding the [M–CO]<sup>·+</sup> ion, which is clearly observed at <i>m</i>/<i>z</i> = 80. Moreover, S 2p and S 2s absorption edges have been examined by measuring the total ion yield spectra in the 160–240 eV region using variable synchrotron radiation. The dynamic of ionic fragmentation following the Auger electronic decay has been evaluated with the help of the PEPIPICO (photoion–photoion–photoelectron–coincidence spectra) technique.