Title：Interstellar fullerene compounds and diffuse interstellar bands

　　Speaker：Prof. Alain Omont (IAP, UPMC)

　　Abstract：The recent confirmation of the presence of interstellar fullerenes and of the first identification of two strong diffuse interstellar bands (DIBs) attributed to C60+ justify trying to reassess the overall importance of interstellar fullerene compounds and the chance they could be carriers of more DIBs. I will first recall the complex properties of fullerenes in interstellar conditions and compare them to better known PAHS, as regards structure, ionization, visible and IR spectra, chemistry, formation/destruction and abundances. I will then briefly review the various classes of possible interstellar fullerenes: pure fullerenes of various sizes and associations with hydrogen, carbon or metal atoms.

　　The first identification of a DIB carrier as C60+ strengthens the proposition that fullerenes could be DIB carriers. Nevertheless, it seems unlikely that most fullerene compounds might be carriers of strong DIBs, with the exception of a few abundant ions, such as C60+, and perhaps other pure fullerenes, fulleranes, or carbon adducts, while a few metallo- or hetero-fullerenes might even be considered. On the other hand, it seems probable that various fullerene compounds might account for some weak DIBs. The lack of precise information about the very complex optical spectra and interstellar abundances still precludes definitive assessment of the importance of fullerenes as DIB carriers. However, the detection of C60+ confirms that fullerenes may be serious candidates, although it seems unlikely that they are the only important DIB carriers. Anyway, DIBs might be the most promising way of tracing the interstellar abundances of a number of fullerene compounds.

　　Time：March 28 (Monday), 10:30am

　　Place：Room 402, Astronomy Building

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　　                                              南京大学天文与空间科学学院