Hydrocarbon growth via ion-molecule reactions: computational studies of the isomers of C4H2+, C6H2+ and C6H4+ and their formation paths from acetylene and its fragments

Abstract

We seek insight into the origin of observations made in plasma experiments mimicking interstellar and circumstellar conditions. To this end theory is applied to the low-energy isomers of C₄H₂⁺, C₆H₂⁺ and C₆H₄⁺ and their formation paths from acetylene and its fragments. Ab initio molecular dynamics trajectories are performed to explore which isomers are readily accessible from acetylene and its ion fragments. Structural information at a high level of electronic structure theory [CCSD(T)/cc-pVTZ], as well as information on the vibrational [UMP2] and electronic spectra [ωB97X] of the low-energy isomers is reported.