PHOSPHORESCENCE OF C(60) AT 1.2-K

Phosphorescence has been observed at 1.2 K both for C60 dissolved in a decaline/cyclohexane glass and for single crystals of C60. The phosphorescence spectrum of C60 in the glass reveals a weak origin at 798.1 +/- 0.5 nm, while most of the intensity shows up in vibronic transitions. The phosphorescence of crystalline C60 consists of two parts. One of these, with the origin of its phosphorescence spectrum at 826 nm, derives probably from a shallow C60 X-trap although an excitonic origin cannot be excluded. The other, with the origin of its phosphorescence spectrum at 862 nm, originates from triplet states previously recognized by magnetic resonance experiments. These concern excitations delocalized over pairs of C60 molecules, so-called mini-excitons that are deep X-traps in the C60 crystal.