Laser-induced fragmentation of coronene cations

TL;DR

This study investigates how coronene cations break apart under light exposure, revealing pathways that could lead to the formation of complex carbon molecules like C60 in space.

Contribution

It combines experimental mass spectrometry with theoretical calculations to elucidate the photodissociation mechanisms of coronene cations relevant to astrochemistry.

Findings

Identification of fragmentation channels producing Cn+ and CnHx+

Observation of dominant peaks at C11+ and C7H+

Proposal of a ring isomerisation pathway for molecule formation

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 (Cn+) and hydrocarbon chains (CnHx+). 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 to 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.