Ionization energies of fullerenes - size and charge dependence

New results from theoretical investigations for the first and higher ionization energies of fullerenes over a wide size range ( - ) are presented. The calculated ionization energies are in very good agreement with available experimental data. The ionization energies decrease roughly as towards an asymptotic value close to the bulk work function of graphite. Such behaviour could be explained by the simple classical electrostatic model of a uniformly charged hollow sphere for the fullerene cluster. Besides fluctuations in the ionization energy as a function of size a systematic deviation from the classical behaviour can be seen, similar to that known from alkaline metal clusters. The electrostatic model can also explain the linear relationship between the calculated ionization energies and the charge state of the fullerene cluster.