Laser photodetachment of C60− and C70− ions cooled in a storage ring

Results are reported of a new type of experiment in which a heavy ion storage ring is utilized to cool fullerene ions, C60− and C70−, and to carry out laser photodetachment experiments in order to measure the electron affinities of ions possessing the minimum amount of internal energy. Fullerene negative ions are stored in the ring for periods of up to 5 s, and the time evolution of the electron affinity is measured, yielding limiting values of 2.666 ± 0.001 and 2.676 ± 0.001 eV for cold C60− and C70−, respectively.