Direct Observation of C 60 Exciton

Photoexcitation of pure C60 thin films by picosecond absorption spectroscopy reveals a transient species with absorption maxima at 540 nm and 660 nm which is assigned to the exciton. Considering the dynamic behaviour of this species and luminescence properties of solid C60, it is concluded that a singlet exciton is observed both in its free (τ1/2 < 15 ps) and self-trapped (τ1/2 = 250 ns) forms.