The quantum yield of ionization

The mechanisms by which "superexcited" states decay are summarized. Experimental studies aimed at deducing these mechanisms for diatomic, triatomic, and polyatomic molecules are reviewed and examined for patterns. From this analysis, dominant mechanisms are identified. Thereupon, an explanation is offered for the observation that the quantum yield of ionization approaches unity at similar to 20 eV, regardless of molecular size. A concomitant conclusion is that large molecules should ionize effectively, contrary to a recent conjecture.