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Self-trapped polaron exciton in neutral fullerene C60.

The luminescence of C 60 was investigated as a function of temperature between 300O and 10 K and for various oxygen concentrations. Its intensity was found to increase strongly with decreasing temperature down to about T 1 =100 K and to decrease again for a further reduction of T. Below 100 K, new structures appeared in the spectra. The experiments are described by a self-localized polaron exciton and by a diffusing free exciton above and below T 1 , respectively