Evidence for the Formation of Interstellar Ions in the Dissociative Photoionization Process of Carbonylsulfenyl Compounds in the 100-1000 eV Region

MARIANA GERONÉS; LUCAS S. RODRÍGUEZ PIRANI; MAURICIO F. ERBEN; ROSANA M. ROMANO; REINALDO L. CAVASSO FILHO; CARLOS O. DELLA VÉDOVA

Campinas

Workshop; International Symposium workshop on astrochemistry, ISWA. Understanding extraterrestrial molecular complexity through experiments and observations; 2016

The photofragmentation processes occurring under synchrotron radiation conditions are very interesting and varied. From the many species formed during the synchrotron experiments reported in the present work at least two call our attention, HCS+ and H3+.1-3 The thioformyl ion is not only one of the more than 140 species recognized in the interstellar medium up to date but one of the key species to understand the interstellar sulfur chemistry. Its C=S bond is extremely strong and the abundance ratio HCS+/CS+ observed in the interstellar medium was found to be unusually higher than the theoretical predictions. This is due to its low recombination energy (charge transfer reactions are inhibited therefore) and the relatively large proton affinity of CS which inhibits proton transfer from HCS+ to most molecular species. The high stability of the interstellar HCS+ ion can be observed over the whole range of photon energies analyzed in our work. The formation of H3+ is quite remarkable since three C−H bonds of the CH3 moiety have to be broken and three new H−H bonds have to be formed. In contrast with the first remarked HCS+, H3+ presents a high acidity. Its proton donor ability serves to initiate ion−molecule reactions in the interstellar medium. In this medium its formation is clearly dependent on both abundant H2 and H2+ species. The production of H3+ via the photodissociation of interstellar methyl compound organic molecules like methanol, methylamine, and acetonitrile was also studied at the LNLS by using photoelectron−photoion coincidence techniques employing soft X-ray photons.