The dissociation dynamics of internal energy selected C6H6+ a)

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Abstract
Absolute fragmentation rates and average energy released in the gas phase dissociation of 2,4 and 1,5 hexadiyne have been measured by photoion–photoelectron coincidence. The decay rates over the metastable energy range, as measured by the asymmetric time‐of‐flight distributions of C4H4+ and C3H3+ fragments are identical, and equal to those measured by others for benzene. This indicates that over this energy range all three C6H6+ isomers rearrange to a common ion structure prior to dissociation. Calculated rates based on the statistical theory suggest that the C6H6+ ions fragment to all product channels by competitive pathways and that the existence of isolated states or noncommunicating isomeric structures is highly unlikely. Above this energy range, the branching ratios to the C3H3+ and C4H4+ fragments indicate that the 1,5 hexadiyne ion no longer isomerizes prior to dissociation.