External heavy atom induced phosphorescence emission of fullerenes: the energy of triplet C60

Abstract

The external heavy atom induced phosphorescence of C60 and C70 is
\nobtained at 77 K in a glass containing ethyl iodide and gives 12 690
\n+/- 30 cm-1 as a precise lower limit for thc energy of triplet C60.
\nTriplet lifetime measurements show that the heavy atom effect is
\nrelatively much greater on the S1 --> T1 than on the T1 --> S0
\nradiationless transitions, as expected from the smaller Franck-Condon
\nconstraints in the former process.