Dissociative photoionization of FSO2NCO following sulfur 2p and 2s edges

Full text: As a part of project aimed to the study of the photochemical and electronic properties of molecules that possess the -XSO2- group (X halogen) namely Photoexcitation, photoionization and photofragmentation studies of molecules with atmospheric interest, in the present work we present a study of the fluorosulphuryl isocyanate, FSO2NCO. Very recently, a similar experimental study was carried out at LNLS for the related molecule ClSO2NCO. The sample was prepared by the fluorination of ClSO2NCO using SbF3 and subsequent trap-to-trap distillation in a vacuum line[1]. The purity of the compound was carefully checked by infrared spectroscopy. The experiments have been performed using synchrotron radiation from the TGM beam line in the range 100-300 eV. The Total Ion Yield spectrum (TIY) of FSO2NCO is dominated by a group of bands centered at 171.0, 172.4, 173.8, 175.2, and 176.2 eV and a small shoulder at 177.2 eV. The S 2p threshold is located at approximately 183.0 eV. In addition, the S 2s threshold was also observed in the TIY spectrum at 237.2 eV. The photoelectron-photoion coincidence (PEPICO) and photoelectron-photoion-photoion coincidence (PEPIPICO) spectra were measured at the most important S 2p transitions, below and above the ionization edge. The analysis of the PEPICO spectra reveals a decrease of the intensity of the heaviest ions when the incident photon energies were increased. The most noticeable change observed by going toward higher energies is the increment of the signal corresponding to the O+ ion from 13 % at 160 eV to 41 % at 237 eV. On the other hand, several islands were observed in the PEPIPICO spectra, presenting the C+/O+, N+/O+, F+/O+, NC+/O+, CO+/O+, S+/O+, NCO+/O+ and SO+/O+ coincidence the higher intensities. [1] R. M.S. Alvarez,E.H. Cutin, H.G. Mack and C. O. Della Vedova, J. Mol. Struct, 323 (1994) 29-38. (author)