Evidence for the Formation of an Interstellar Species, HCS+, during the Ionic Fragmentation of Methyl Thiofluoroformate, FC(O)SCH3, in the 100−1000 eV Region

Abstract

Total ion yield spectra and photoinduced fragmentations following S 2p, C 1s, O 1s, and F 1s inner shell excitations of methyl thiofluoroformate, FC(O)SCH(3), have been studied in the gaseous phase by using synchrotron radiation and multicoincidence techniques, which include photoelectron-photoion coincidence (PEPICO) and photoelectron-photoion-photoion coincidence (PEPIPICO) time-of-flight mass spectrometry. Fragmentation patterns deduced from PEPICO spectra at the various excitation energies show a moderate site-specific fragmentation. The dissociation dynamic for the main ion-pair production has been discussed. Two-, three-, and four-body dissociation channels have been observed in the PEPIPICO spectra, and the dissociation mechanisms were proposed. The high stability of the interstellar HCS(+) ion can be observed over the whole range of photon energies analyzed.