PHOTOIONIZATION THRESHOLD STRUCTURE OF FULLERENES - VIBRATIONAL-EXCITATION

The threshold region of the photoionization spectra of fullerenes show s distinct changes of slope which are typical for the opening of addit ional channels due to vibrational excitation. Typically, after evapora tion from a hot oven, C-60 is excited in all its vibrational modes. Th rough coupling with the ionization transition only the two highly symm etric modes (breathing mode and tangential stretch mode) can be excite d or de-excited. An analysis of the C-60 data reveals very good agreem ent of the observed structure with the expected energetic positions of various combinations of excitation and de-excitation of these two mod es.