SEARCH FOR FULLERENES AND PAHS IN THE DIFFUSE INTERSTELLAR-MEDIUM

Recent studies suggest carbon-containing molecules as the best candidates for carriers of the unidentified diffuse interstellar bands (DIBs), considering their abundance and ability to form stable bonds in interstellar space. We have searched for new DIBs in the near-IR and have detected two new diffuse bands that are consistent with laboratory measurements of C-60(+) in a neon matrix. Criteria for this possible identification are discussed. From these observations and the DIB measured absorption, we estimate that up to 0.9% of interstellar carbon could be in the form of C-60(+). We also searched for polycyclic aromatic hydrocarbon (PAH) cations and have derived corresponding limits for the presence of the coronene C24H12 and ovalene C32H14 cations in space. We have studied the ionization properties of these PAH cations, which could explain their selective destruction. From these results we discuss the role of fullerenes and PAHs as possible DIB carriers.