Molecular study of HC_3_NH^+^+e^-^

Motivated by the evidence that HCN and its metastable isomer HNC are both formed via the dissociative recombination reaction of HCNH^+^, we have examined the potential energy surface for the dissociation of the transient HC_3_NH following the recombination between HC_3_NH^+^ and electrons.

We find that HC_3_NH^+^ gains 151 kcal mol^-1^ energy by the neutralization; this energy is high enough to isomerize HC_3_NH to HCCNCH, as well as to dissociate a hydrogen atom from either end of the molecule. The present calculation suggests, therefore, that the metastable linear and near-linear isomers of HC_3_N, namely, HNC_3_, HCCNC, and HCNCC, can be formed via the dissociative recombination between HC_3_NH^+^ and electrons.