Electronic Excitations and Stability of the Ground State of C60   Molecules
  A model study of the singlet excitons in the C60 molecule with emphasis on the Coulomb interaction between excited electron and hole leads to a physical understanding of the interaction effects on the absorption spectra and to a new identification of the forbidden excitons in the third-harmonic generation spectra. These conclusions may be tested experimentally on the model predictions related to the optical Kerr effect. The model shows that, with sufficiently strong interatomic than onsite interaction, a T_{2G} exciton could have very low energy or become unstable against the closed-shell ground state. Properties of these interesting cases beyond the C60 are briefly examined. 
F. Bechstedt (1 and 2), M. Fiedler (2) and L.J. Sham (1) ((1)   University of California San Diego, (2) Friedrich-Schiller-U...