Bromobenzene ions, decomposition

The k(E) vs. E curve obtained for bromobenzene using variable residence time [717] also differed from that for bromobenzene of the earlier study [22]. As before, the rate coefficients based on varying the residence time were lower than those from the earlier study of metastable ions. The critical energy was found to be 2.76 0.02 eV and the transition state was loose . Comparison was made with the corresponding neutral decomposition and it was concluded that the ionic decomposition had a marginally lower frequency factor and the lower critical energy (2.76 eV compared with 3.5 eV). The kinetic shift with the bromobenzene ion was about 0.2 eV on lengthening the residence time from 1.13 ps to 5.03 ps. 

The decompositions of bromobenzene [717] and chlorobenzene ions [716] have been studied by the special PIPECO experiment using variable source residence times. In the case of chlorobenzene, increasing the residence time from 0.7 to 8.9 ps resulted in a shift (kinetic shift) in the breakdown curves by 0.4 eV. Detailed analysis of the effects of varying residence time provided information on the k(E) vs. E curve in the vicinity of 104—106 s-1. The k(E) vs. E curve obtained differed significantly [by almost an order of magnitude in k(E) at some energies] from the curve reported in the earlier PIPECO study of metastable ions [22], The initial analysis [716] placed the critical energy for chlorine loss at 3.40 0.05 eV, but this has subsequently been revised to 3.19 0.02 eV [717]. The transition state was found to be loose . 

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