CARBON ONIONS AS POSSIBLE CARRIERS OF THE 2175-ANGSTROM INTERSTELLAR ABSORPTION BUMP

We have studied the ultraviolet (UV) optical response of various hollo w and filled spherical multishell fullerenes (commonly called carbon o nions) in the wavelength region of the carbon pi-plasmon excitation. O ur theoretical approach, which follows a recently proposed growth mode l, allowed us to investigate the modification of the electronic proper ties of these clusters brought about by a material (for example, diamo nd) filling the inner cavity and by a coating layer (for example, wate r). We found that coated onion particles have optical properties consi stent with the UV interstellar dust absorption data, including the con stant position of the absorption maximum associated with a large varia tion of the resonance width.