POLARON EXCITATIONS IN DOPED C60 AND C70

We propose a Su-Schrieffer-Heeger type electron-phonon model for fullerenes: C60 and C70. The model is solved by a numerical iteration method with applying the adiabatic approximation to phonons. When the system (C60 or C70) is doped with one or two electrons (or holes), the additional charges accumulate along almost an equatorial line of the molecule. The dimerization becomes weaker along almost the same line. Two energy levels, the occupied state and the empty state, intrude largely in the gap. The intrusion is larger in C70 than in C60. These are ''polarons'' in doped fullerenes. It is also found that C60 and C70 are related mutually with respect to electronical structures as well as lattice geometries. We also calculate optical properties of C60. In optical absorption of the doped C60, there is a new peak at lower energy than those of the intergap transition peaks. The third harmonic generation of the neutral C60 in low frequencies agrees with experiments. Relations of polarons with recent experiments are pointed out.