A SIFT ion-molecule study of some reactions in Titan's atmosphere.: Reactions of N+, N2+ and HCN+ with CH4, C2H2, and C2H4

The results of a study of the ion-molecule reactions of N+, N-2(+), and HCN+ with methane, acetylene, and ethylene are reported. These studies were performed using the FA-SIFT at the University of Canterbury. The reactions studied here are important to understanding the ion chemistry in Titan's atmosphere. N+ and N-2(+) are the primary ions formed by photo-ionization and electron impact in Titan's ionosphere and drive Titan's ion chemistry. It is therefore very important to know how these ions react with the principal trace neutral species in Titan's atmosphere: Methane, acetylene, and ethylene. While these reactions have been studied before the product channels have been difficult to define as several potential isobaric products make a definitive answer difficult. Mass overlap causes difficulties in making unambiguous species assignments in these systems. Two discriminators have been used in this study to resolve the mass overlap problem. They are deuterium labeling and also the differences in reactivities of each isobar with various neutral reactants. Several differences have been found from the products in previous work. The HCN+ ion is important in both Titan's atmosphere and in the laboratory. (C) 2004 American Society for Mass Spectrometry.