The electronic structure of polymerized fullerenes and dimerized heterofullerenes

\chem{Rb_1C_{60}}

and dimerised \chem{C_{59}N} using electron energy-loss spectroscopy in transmission. From the C1s excitation spectra a reduced density of \pi^\star states is observed for polymerized \chem{Rb_1C_{60}}. This is in contrast to \chem{(\chem{C_{59}N})_2} and can be explained by the different type of \squt{doping} and by the different bonding between the fullerene molecules in the two systems.

Additional information about the optical properties was obtained from the low energy loss function. Using a Kramers-Kronig analysis, the dielectric function, (\epsilon), and the optical conductivity, (\sigma), have been derived. \epsilon(0) and the onset of the spectral weight have been compared between the polymer, the dimer and \chem{C_{60}}. This onset of spectral weight is found to be at \valunit*{1.2}{\eV} and \valunit{1.4}{\eV} for o-\chem{Rb_1C_{60}} and for \chem{(\chem{C_{59}N})_2}, respectively.