THERMIONIC EMISSION AND FRAGMENTATION OF C-60

We analyze the rate of delayed (thermionic) ionization of photoexcited C-60 molecules. The rate has a power-law dependence, indicating the p resence of a continuum of rate constants. The value of the exponent pr ovides information about the competition between delayed ionization an d unimolecular fragmentation; it is equal to the ratio of the ionizati on energy and the activation energy for fragmentation. This result pro vides a novel method to measure the controversial bond dissociation en ergy of neutral C-60. We obtain a value of 11.9 +/- 1.9 eV.