C60 fullerene as a pseudoatom of the icosahedral symmetry

Unique features of the electronic structure and spectra of the C₆₀ (I_h) fullerene and its ions related to the icosahedral symmetry are discussed. The so-called ′accidental′ degeneracy of terms in the open electron shells g^N and h^N (corresponding to four- and fivefold degeneracy of molecular orbitals, respectively) and the abnormal (′non-Bethe′) splitting of terms in the h^N 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 C₆₀^m± ions based on representation of the C₆₀ (I_h) 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 C₆₀^m± 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.