Optical Absorption in Higher Fullerenes: Effects of Symmetry Reduction

Optical absorption spectra of higher fullerenes (C70 and C76) as well as of C60 are calculated by a tight binding model with a long range Coulomb interaction. A reasonable parameter set gives calculated spectra which are in overall agreement with the experiments of of C60 and C76 in solutions. The variations of the spectral shape are discussed relating with the symmetry reduction going from C60 and C70 to C76: the optical gap decreases and the spectra have more small structures in the dependences on the excitation energy. Keywords: optical absorption, fullerene, C60, C70, C76, CI calculation, theory