1995A&A...299..213E

Recent studies suggest carbon-containing molecules as the best candidates for the carriers of the unidentified diffuse interstellar bands (DIBs), considering their abundance and ability to form stable bonds in interstellar space. The spectra of the naphthalene and pyrene cations in a neon matrix were recently reported, indicating a link between these small polycyclic aromatic hydrocarbon (PAH) ions and some diffuse bands. We have searched for new DIBs in the near-infrared and around 4592A in order to identify the coronene (C₂₄H₁₂) and ovalene (C₃₂H₁₄) cations in the diffuse medium. Due to their pericondensed structure these molecules should be among the most stable PAHs in the interstellar medium. The absorption spectra of both molecules were recently measured in solid neon. We report on the search for the bands at 9465/4592A and 9780A, and derive corresponding limits on the presence of the coronene and ovalene cations in the diffuse interstellar medium. From these results, we discuss a possible selective destruction mechanism of PAHs through dication formation, and the role of PAH compounds as possible DIB carriers.