Dissociation mechanisms of SO2 containing molecules after photoexcitation with synchrotron radiation in the energy range between 100 and 1000 eV.

ANGÉLICA MORENO BETANCOURT; BAVA YANINA BELÉN; CAVASSO FILHO R. L.; DELLA VÉDOVA CARLOS O.; ERBEN MAURICIO F.; GERONÉS MARIANA; ROMANO ROSANA M.

Campinas

Congreso; 23ª Reunião Anual de Usuários do LNLS/CNPEM Laboratório Nacional de Luz Síncrotron; 2013

Laboratório Nacional de Luz Síncrotron

Dissociation mechanisms of SO2 containing molecules after photoexcitation with synchrotron radiation in the energy range between 100 and 1000 eV.Recent investigations in our research group have been dedicated to the elucidation of photochemical reaction mechanisms between small molecules that are relevant as atmospheric contaminants or components. For example the photochemical gas-phase reaction between SO2, O2 and Cl2 was studied and the reaction mechanisms were proposed on the basis of the isolation and identification of the products. Molecules of the type ClSO2(OSO2)nCl, with n=1,2 and the novel peroxide ClSO2OOSO2Cl were determined, among others, as the main photoproducts. On the frame of a general project aimed to the elucidation of the photochemical and electronic properties of molecules containing the XSO2- group, with X=halogen, we present here the study of the of the ionic photofragmentation of three compounds of this family: (ClSO2)2O, FSO2NCO and ClSO2NCO, after core-shell excitation of C 1s, N 1s, O 1s, and F 1s electrons. Photoionization and photofragmentation of the compounds in the energy region between 250 and 1000 eV were studied in the SGM beamline at LNLS, using the experimental station for gaseous samples and coincidence techniques. The detection of ionic fragments in coincidence, PEPIPICO techniques, allows the study of unimolecular photofragmentation mechanisms. At the high excitation energies, the most important processes conduct usually to atomic fragments produced through concerted mechanisms. Nevertheless, in the three molecules studied here several polyatomic ionic fragments were detected in coincidence. The NCO+/SO+ coincidence was observed for FSO2NCO and interpreted as a four-body secondary decay after differed charge separation mechanisms. It is worth to mention that this coincidence was not observed in the case of ClSO2NCO, for which most of the fragmentation mechanisms involve atomic fragments. On the other hand, the SO2 + ion was produced from (ClSO2)2O by several different mechanisms.