VIBRONIC STRUCTURE AND RESONANCE EFFECTS IN THE OPTICAL-SPECTRA OF THE FULLERENES C-60 AND C-70

Optical emission spectra of solid C-60 and C-70 were recorded at 1.9 K using different detector systems. In the region of low energy an impr oved resolution could be obtained using an IR sensitive photodiode. Th e energy of the emitting states of C-60 was estimated by means of reso nant excitation using a dye laser. The proposed assignment of the vibr ational fine structure is based on vibrational frequencies obtained fr om normal coordinate analysis and CNDO/S-calculated intensities of fal se origins, both reported in the literature. It is shown that the emis sion arises from two electronic states. Low-energy excitation of C-70 supplies evidence for two emitting states as well. Resonance excitatio n supplies specific changes of the emission spectrum attributed to dif ferent excited levels.