Electronic Properties of FC(O)SCH₂CH₃. 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)­SCH₂CH₃, 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_π(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]^·+ 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

Electronic Properties and Dissociative Photoionization of Thiocyanates. Part II. Valence and Shallow-Core (Sulfur and Chlorine 2p) Regions of Chloromethyl Thiocyanate, CH₂ClSCN

A combination of photoelectron spectroscopy and synchrotron based photoelectron photoion coincidence (PEPICO) spectra has been applied to investigate the electronic structure and the dissociative ionization of the CH₂ClSCN molecule in the valence region. The PES is assigned with the electronic structure calculations at the outer-valence Green’s function and symmetry adapted cluster/configuration interaction (SAC-CI) levels offer an explanation of our experimental results. Upon vacuum ultraviolet irradiation the low-lying radical cation, located at 10.39 eV is formed. The molecular ion is observed in the time-of-flight mass spectra, together with the CH₂SCN⁺ and CH₂Cl⁺ daughter ions. The total ion yield spectra have been measured in the S 2p and Cl 2p regions and several channels have been determined in dissociative photoionization events for the core-excited species. Thus, by using time-of-flight mass spectrometry and synchrotron radiation the relative abundances of the ionic fragments and their kinetic energy release values were obtained from both PEPICO and photoelectron photoion photoion coincidence spectra. Possible fragmentation processes are discussed and compared with that found for the related CH₃SCN species