Radiative cooling of fullerene anions in a storage ring

Thermionic emission from hot fullerene anions, CN, has been measured in an electrostatic storage ring for even N values from 36 to 96. The decay is quenched by radiative cooling and hence the observations give information on the intensity of thermal radiation from fullerenes. The experiments are analysed by comparison with a simulation which includes the quantisation of photon energy and the statistics of emission. Experiments with heating of the molecules with a laser beam confirm the interpretation of the observations in terms of radiative cooling and give an independent estimate of the cooling rate for C-60(-). The measured cooling rates agree in general within a factor of two with the prediction from a classical dielectric model of a thermal radiation intensity of similar to 300 eV/s for C-60 at 1 400 K, scaling approximately with the 6th power of the temperature and with the number of atoms in the molecule.