We have measured the absolute rates of X loss from metastable, energy selected, C6H5X+ (X=Cl, Br, I) ions. A photoion–photoelectron coincidence technique was used to collect time of flight distributions of fragment ions formed from precursor ions with selected internal energies. The measured rates, which are between 6×104 and 3×106 sec−1, are compared with predictions of the statistical theory of unimolecular reactions. Over the energy range covered (0.7 to 1.7 eV above the reaction threshold) the agreement between experiment and theory is excellent. This agreement is in distinct contrast to a similar investigation of the rates of C4H6+ fragmentation which, at the reaction threshold, were three orders of magnitude faster than predicted.
Topics
Statistical models
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