The discovery and synthesis of fullerenes led to the hypothesis that fullerene
compounds may be present and stable in interstellar space. As first evidence
for the largest molecule ever detected in space, we have recently detected two
new diffuse interstellar bands (DIBs) that are consistent with laboratory
measurements of the C60 cation. From these observations we estimate that up to
0.9 % of interstellar carbon could be in the form of C60+. This suggests that
fullerenes may play an important role in interstellar chemistry.
We propose to observe with ISO SWS the vibrational transitions of the fullerene
C60 (neutral, cation and anion), as well as the transitions of exohedral
fullerene compounds formed with H or metals such as Na, K. The wavelength
positions and oscillator strengths of these transitions are derived from
recent laboratory measurements in Ne matrices.
Fullerene compounds may be present as neutral and ionized species in the
diffuse interstellar medium and dominantly neutral in dense clouds. We intend
to observe extincted targets in the diffuse interstellar medium, embedded
protostars in dense molecular clouds and potential progenitor sources (C
stars). These observations will provide the abundances of fullerenes species in
lines of sight for which visible diffuse interstellar bands, attributed to the
C60 cation, have been measured. The general aim of this proposal is to contrain
the production, stability and role of fullerenes in interstellar chemistry.