Laser-induced fragmentation of coronene cations.

Polycyclic aromatic hydrocarbons are an important component of the interstellar medium of galaxies and photochemistry plays a key role in the evolution of these species in space. Here, we explore the photofragmentation behaviour of the coronene cation (C 24 H 12 ˙ + ) using time-of-flight mass spectrometry. The experiments show photodissociation fragmentation channels including the formation of bare carbon clusters (C n ˙ + ) and hydrocarbon chains (C n H x + ). The mass spectrum of coronene is dominated by peaks from C 11 ˙ + and C 7 H + . Density functional theory was used to calculate relative energies, potential dissociation pathways, and possible structures for relevant species. We identify 6-6 → 5-7 ring isomerisation as a key step in the formation of both the bare carbon clusters and the hydrocarbon chains observed in this study. We present the dissociation mechanism outlined here as a potential formation route for C 60 and other astrochemically relevant species.