Vibrational signatures of fullerene oxides

Raman and IR spectra of C60, C60O, C120O and C120O2, measured at room temperature, are discussed using geometric structures, normal modes, Raman and IR intensities from density functional-based tight-binding (DF-TB) calculations. An assignment of the most important vibrational modes is given. In the studied compounds the splitting of the C60 modes is explained by the removal of degeneracy and the vibrational coupling between the C60 cages. Strong IR absorptions of both dimeric oxides between 950 and 1150 cm-1 are assigned to the furan-like structures connecting the buckyballs. The inter-ball Raman lines below 200 cm-1 are shown to be dependent on the bonding strength between the cages. Both the bridge-based IR absorptions and the inter-ball Raman modes are suitable for the identification of the nature and number of bridging structures in oligomeric fullerene oxides.