Termination of bottom-up interstellar aromatic ring formation at C6H5+

The aromatic molecule benzene is considered to be the essential building block for larger polycyclic aromatic hydrocarbons (PAHs) in space. Despite the importance of benzene in the formation of PAHs, the formation mechanisms of interstellar benzene are not well understood. A single ion–molecule reaction sequence is considered when modelling the formation of benzene in the interstellar medium, beginning with the protonation of acetylene. Although this process has been used to model the initial steps in the formation of PAHs, it has not been experimentally measured.