Direct Observation of C 60 Exciton

Photoexcitation of pure C 60 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 C 60 , it is concluded that a singlet exciton is observed both in its free (τ 1/2 < 15 ps) and self-trapped (τ 1/2 = 250 ns) forms.