Bimolecular reactions of CH 2 CN 2+ with Ar, N 2 and CO: reactivity and dynamics.

The reactivity, energetics and dynamics of bimolecular reactions between CH 2 CN 2+ and three neutral species (Ar, N 2 and CO) have been studied using a position sensitive coincidence methodology at centre-of-mass collision energies of 4.3-5.0 eV. This is the first study of bimolecular reactions involving CH 2 CN 2+ , a species relevant to the ionospheres of planets and satellites, including Titan. All of the collision systems investigated display two collision-induced dissociation (CID) channels, resulting in the formation of C + + CH 2 N + and H + + HC 2 N + . Evidence for channels involving further dissociation of the CID product HC 2 N + , forming H + CCN + , were detected in the N 2 and CO systems. Proton-transfer from the dication to the neutral species occurs in all three of the systems via a direct mechanism. Additionally, there are product channels resulting from single electron transfer following collisions of CH 2 CN 2+ with both N 2 and CO, but interestingly no electron transfer following collisions with Ar. Electronic structure calculations of the lowest energy electronic states of CH 2 CN 2+ reveal six local geometric minima: both doublet and quartet spin states for cyclic, linear (CH 2 CN), and linear isocyanide (CH 2 NC) molecular geometries. The lowest energy electronic state was determined to be the doublet state of the cyclic dication. The ready generation of C + ions by collision-induced dissociation suggests that the cyclic or linear isocyanide dication geometries are present in the [CH 2 CN] 2+ beam.