Abstract
The valence electronic properties of S-ethyl flouromethanethioate (S-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 [nπ(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 m/z = 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.
Highlights
Very detailed studies on the photoionization and dissociative ionization processes of molecules in the gas phase can be accomplished by using synchrotron radiation and mass-spectrometry techniques in the multicoincidence mode.[1]
The CH2CH2SH2+ β-distonic radical cation was detected as the product of decarbonylation of HC(O)SCH2CH3 in the 70 Energy Release Values (eV) electron-impact mass-spectrum.[10]
The first investigations related with the conformational properties of ethyl thioesters of general formula XC(O)SCH2CH3 (X= H, Cl, F, CN, CF3) had been performed by True and Bohn by using low resolution microwave spectroscopy.[43]
Summary
Very detailed studies on the photoionization and dissociative ionization processes of molecules in the gas phase can be accomplished by using synchrotron radiation and mass-spectrometry techniques in the multicoincidence mode.[1]. The choice of the title species is mainly given by the low mass of the fluorine atom and a wide range of photon energies is applied, which includes the He(I) photoelectron spectra as well as synchrotron-based studies on the valence and the inner-shell S 2p edge. Al[29] have measured the argon TOF spectrum using the same experimental setup, and a peak width value of 0.05 eV was achieved for the Ar+ ion. This value represents a good estimation for the instrumental resolution since the broadening in argon can only be the result of thermal energy and instrument broadening.
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