2022A&A...662A..21Z

Fullerene and polycyclic aromatic hydrocarbon (PAH) molecules, as well as their cations and clusters, are of great interest in astrochemistry. In this work, the ion-molecule collision reaction between fullerene (e.g. a C_54/56/58 and C₆₀ system or a C_64/66/68 and C₇₀ system) monocations and neutral PAHs (e.g. 2,3-benzofluorene, C₁₇H₁₂) is studied in the gas phase to determine the importance of charge exchanges and to illustrate the competition between charge transfer and molecular adduct formation channels. The experimental results show that the charge transfer channel is the dominant channel (i.e. charge exchange) in the reaction between fullerene (C₆₀ and C₇₀) monocations and 2,3-benzofluorene, while the molecular adduct formation channels are the dominant channels in the reaction between fullerene (C_54/56/58 and C_64/66/68) monocations and 2,3-benzofluorene. The observed reaction behaviours are investigated with quantum calculations, and the CH₂ unit binding effect of 2,3-benzofluorene is determined to be the main reason for the results. Our findings on the ion-molecule collision reaction between fullerene monocations and 2,3-benzofluorene provide a good model for understanding the physical-chemical processes of the charge transfer channel and the cluster adduct formation channels. Neutral fullerenes (C₆₀ and C₇₀) increase the abundance of their monocations through collision reactions with coexisting neutral molecules in the interstellar medium.