Laser-induced fragmentation of coronene cations

Area of Science:

• Astrochemistry
• Physical Chemistry
• Interstellar Medium Composition

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are abundant in the interstellar medium.
• Photochemistry is crucial for the transformation of PAHs in space.
• Understanding PAH photofragmentation is key to interstellar chemistry.

Purpose of the Study:

• To investigate the photofragmentation behavior of the coronene cation (C24H12˙+).
• To elucidate the fragmentation pathways and resulting species.
• To explore potential formation routes for astrophysically relevant molecules like C60.

Main Methods:

• Experimental photofragmentation using time-of-flight mass spectrometry.
• Theoretical calculations using density functional theory (DFT).
• Analysis of relative energies, dissociation pathways, and molecular structures.

Main Results:

• Coronene cation photodissociation yields bare carbon clusters (Cn˙+) and hydrocarbon chains (CnHn˙+).
• Dominant fragments observed were C11˙+ and C7H+.
• Identified 6-6 → 5-7 ring isomerisation as a critical step in fragmentation.

Conclusions:

• The study outlines a detailed photofragmentation mechanism for the coronene cation.
• This mechanism provides insights into the formation of carbon clusters and hydrocarbon chains in space.
• The proposed pathway is a potential route for the formation of C60 and other astrochemically significant species.