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MO: Fachverband Molekülphysik

MO 2: Collisions, Energy Transfer

MO 2.5: Vortrag

Montag, 8. März 2010, 15:00–15:15, F 142

Isomers in Space - Dissociative Recombination of ²HCN²H⁺ — •Mario B. Mendes¹, Henrik Buhr^{2, 1}, Oldřich Novotný¹, Max H. Berg¹, Dennis Bing¹, Michael Froese¹, Manfred Grieser¹, Brandon Jordon-Thaden¹, Claude Krantz¹, Steffen Novotny¹, Dmitry A. Orlov¹, Annemieke Petrignani¹, Julia Stützel¹, Oded Heber², Michael L. Rappaport², Dirk Schwalm^{2, 1}, Daniel Zajfman², and Andreas Wolf¹ — ¹Max-Planck-Institut für Kernphysik, Heidelberg, Germany — ²Faculty of Physics, Weizmann Institute of Science, Rehovot, Israel

Hydrogen cyanide (HCN) and its energetically higher lying isomer hydrogen isocyanide (HNC) play an important role in the chemistry of dense molecular clouds within the interstellar medium. Despite the fact that HNC is less stable than HCN, its abundance is of the same order of magnitude. In order to explain this unusual abundance ratio, it has been proposed that both isomers are formed with the same efficiency in dissociative electron-ion recombination of HCNH⁺. Although this hypothesis has been discussed for more than 35 years now, there is still no convincing experimental evidence.

We studied the dissociative recombination of DCND⁺ in a storage ring experiment at the TSR, Heidelberg, using a new mass-sensitive fragment imaging detector. Surprisingly, DCN/DNC is mostly produced in vibrationally excited states, well above the isomerization barrier. The final branching ratios are fixed by radiative relaxation. This presents the formation of the two isomers in a new light, supporting the assumption that both of them are produced in this process.