C60 fullerene as a pseudoatom of the icosahedral symmetry

Abstract

Unique features of the electronic structure and spectra of the C60 (Ih) fullerene and its ions related to the icosahedral symmetry are discussed. The so-called ′accidental′ degeneracy of terms in the open electron shells gN and hN (corresponding to four- and fivefold degeneracy of molecular orbitals, respectively) and the abnormal (′non-Bethe′) splitting of terms in the hN configuration are considered. The need to describe these terms arises in studies of ionized and excited states of the C60 molecule and its derivatives. A novel approach to the description of C60m± ions based on representation of the C60 (Ih) fullerene as a (pseudo)atom of icosahedral symmetry is considered in detail. The approach involves an expansion of the molecular orbitals of C60 in terms of the atomic orbitals centred at the origin (at the centre of the C60 molecule) and a multipole expansion of the electron repulsion. The energy spectra of the fullerene and C60m± ions, the magnetic moments and optical dipole transitions are considered. The results obtained are compared with those of ab initio calculations and with the available experimental data.