Delayed ionization of C60:: The competition between ionization and fragmentation revisited

We reconsider the competition between delayed ionization and neutral fragmentation of C-60 as observed on the microsecond time scale. Experimental data are compared with numerically calculated ionization rates allowing for three competing decay channels: thermionic emission, neutral fragmentation, and radiative cooling. The value of the neutral dissociation energy extracted from the analysis of the power law behavior of the ionization rate for delays up to 10 mus was found to be significantly larger than previously reported. The unreasonably high values obtained in combination with the strong deviation from power law behavior for delay times longer than 10 mus has prompted a reinterpretation of the experimental results in terms of delayed ionization from electronically excited fullerenes in the lowest triplet state. (C) 2001 American Institute of Physics.