LABORATORY STUDY OF CARBON PARTICLES AND CLUSTERS

To investigate the role of pure carbon in interstellar absorption, optical spectroscopy on laboratory-produced carbon grains, C60 Buckminsterfullerene and small carbon clusters has been carried out. The results obtained so far are: (a) The UV absorption of small (diameter ca. 10 nm) carbon grains depends strongly on the atomic structure of the grain material. A fit of the laboratory data to the interstellar 217 nm feature by graphitic grains seems to be possible provided some serious experimental problems can be overcome. (b) There is so far no clear-cut coincidence between the measured spectra of neutral and ionised C60 and the known interstellar bands in the UV and IR. (c) The spectra of carbon clusters (C5-ca. C-11) trapped in cryogenic matrices show great similarities to the pattern of diffuse interstellar bands in the visible range.