Isomer effects in fragmentation of Polycyclic Aromatic Hydrocarbons

[Display omitted] •Three sets of isomeric Polycyclic Aromatic Hydrocarbon cations were studied.•Collisions with He at center-of-mass energies around 100eV.•Significant differences in product distributions, notably CHx-loss (carbon knockout).•Competition between statistical and non-statistical fragmentation.•The CHx-loss cross section is correlated with the parent ion ground state energy. We have observed significant differences in the fragmentation patterns of isomeric Polycyclic Aromatic Hydrocarbon (PAH) cations following collisions with helium atoms at center-of-mass energies around 100eV. This is in contrast to the situation at other collision energies or in photo-absorption experiments where isomeric effects are very weak and where the lowest-energy dissociation channels (H- and C2H2-loss) dominate in statistical fragmentation processes. In the 100eV range, non-statistical fragmentation also competes and is uniquely linked to losses of single carbon atoms (CHx-losses). We find that such CHx-losses are correlated with the ionic ground state energy within a given group of isomers. We present results for three C16H10+, four C18H12+ and five C20H12+ isomers colliding with He.