PHOTODISSOCIATION DYNAMICS OF METHYLAMINE CATION AND ITS RELEVANCE TO TITAN'S IONOSPHERE

Abstract

Photodissociation of CH3NH2 + has been studied using the DC sliced ion imaging technique and ab initio calculations in order to understand the formation of HCNH+, an important molecule in Titan's ionosphere. Our experimental and theoretical observations show that hydrogen loss from CH3NH2 + has two channels: one giving rise to the triplet species CH3NH+, while the other product is CH2NH2 +. The latter then decomposes further to form HCNH+. H2 loss from CH3NH2 + has only one channel, yielding CH2NH+. This species further loses H to form HCNH+. The branching ratio of the H, H2, and H+H2 loss channels is found to be 4.2:1:2.5. This is ascribed to the fact that, at these energies, the H loss has one stable triplet product channel, while most of the H2 loss product further decomposes to HCNH+.