LOWEST EXCITED SINGLET-STATE OF C-60 - A VIBRONIC ANALYSIS OF THE FLUORESCENCE

The fluorescence and fluorescence-excitation spectra of C-60 in a hydr ocarbon glass at 1.2 K are reported. The fluorescence spectrum resembl es that of a molecular X-trap in crystalline C-60. The vibronic bands in these spectra are assigned, and the intensity distribution among th e false origins points to vibronic coupling within the singlet manifol d. The lowest excited singlet state of C-60 shows predominantly T-1g a nd G(g) character. Additionally, we show that a reduction of the symme try of C-60 by either an intra- or an intermolecular perturbation lead s to a fluorescence spectrum with a strong 0-0 transition and a differ ent vibronic structure.