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Volume 13: Pages 248-255, 2000
The Quantum Yield of Ionization
1Chemistry Division, Argonne National Laboratory, Argonne, IL 60439 U.S.A.
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 20 eV, regardless of molecular size. A concomitant conclusion is that large molecules should ionize effectively, contrary to a recent conjecture.
Keywords: superexcited states, resonant autoionization, direct ionization, electronic autoionization, predissociation, vibrational autoionization, radiationless transition, quantum yield
Received: August 31, 2000; Published online: December 15, 2008