Similarities and dissimilarities in the fragmentation of polycyclic aromatic hydrocarbon cations: A case study involving three dibenzopyrene isomers

Abstract

The photon induced fragmentation behavior of the cations of three dibenzopyrene (C24H14) isomers (DBPae, DBPah and DBPal) is studied in a series of systematic mass spectrometric experiments. The ions are collected in an ion trap system and irradiated with different numbers of photons before being released into a time-of-flight mass spectrometer. The resulting mass spectra show a number of remarkable similarities, despite the structural differences between the three precursor species. Differences in the fragmentation patterns are found as well. Whereas it is not straight forward to explain the molecular origin of these findings, it is clear that the observed fragmentation patterns are relevant to further interpret the molecular composition of the interstellar medium (ISM), in which PAHs are omnipresent and subject to intense radiation. The main conclusion of this work is that PAHs comparable to the one studied here, may enrich the ISM with pure carbon species, Cn+, with n values roughly between 11 and 15, following a top-down approach.