Delayed ionization of C-60: The competition between ionization and fragmentation revisited

We reconsider the competition between delayed ionization and neutral fragme ntation of C-60 as observed on the microsecond time scale. Experimental dat a are compared with numerically calculated ionization rates allowing for th ree competing decay channels: thermionic emission, neutral fragmentation, a nd radiative cooling. The value of the neutral dissociation energy extracte d from the analysis of the power law behavior of the ionization rate for de lays up to 10 mus was found to be significantly larger than previously repo rted. The unreasonably high values obtained in combination with the strong deviation from power law behavior for delay times longer than 10 mus has pr ompted a reinterpretation of the experimental results in terms of delayed i onization from electronically excited fullerenes in the lowest triplet stat e. (C) 2001 American Institute of Physics.