Laser-induced fragmentation of coronene cations

Abstract

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 (C₂₄H₁₂˙⁺) 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_nH_x⁺). The mass spectrum of coronene is dominated by peaks from C₁₁˙⁺ and C₇H⁺. 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 C₆₀ and other astrochemically relevant species.