The dissociation dynamics of internal energy selected C6H6+ a)

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.