Delayed ionization and fragmentation en route to thermionic emission: Statistics and dynamics

Thermionic emission is discussed as a long time (microseconds) decay mode o f energy-rich large molecules, metallic and metcar clusters, and fullerenes . We review what is known and consider the many experiments, systems, and t heoretical and computational studies that still need to be done. We conclud e with a wish list for future work. Particular attention is given to the ex perimental signatures, such as the dependence on the mode of energy acquisi tion, and theoretical indications of a not-quite-statistical delayed ioniza tion and to the competition of electron emission with other decay modes, su ch as fragmentation or radiative cooling. Coupling of the electronic and nu clear modes can be a bottleneck and quite long time-delayed ionization can be observed, as in the decay of high Rydberg states probed by ZEKE spectros copy, before the onset of complete energy partitioning.