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A structural investigation of [C 6 H 6 ] 2+ and [C 6 H 6 ] + ˙ ions involved in charge exchange reactions
Author(s) -
Guilhaus M.,
Kingston R. G.,
Brenton A. G.,
Bey J. H.
Publication year - 1985
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210200907
Subject(s) - dication , ion , chemistry , benzene , mass spectrum , electron ionization , ionization , analytical chemistry (journal) , electron capture , spectral line , molecule , atomic physics , physics , organic chemistry , chromatography , astronomy
Mass‐analysed ion kinetic energy spectra for collisional activation (CA) of [C 6 H 6 ] + ˙ formed via electron capture by [C 6 H 6 ] 2+ ions in collision with neutral benzene molecules have been compared for the C 6 H 6 isomers benzene, 1,5‐hexadiyne and 2,4‐hexadiyne. Comparisons of fragment abundance and total CA fragment yields were also made for [C 6 H 6 ] + ˙ ions generated by electron ionization (EI). CA conditions of ion velocity and collision gas pressure were identical in these comparisons. In general the fragment abundance patterns for the ions formed by charge exchange were very similar to those for singly charged benzene ions generated by EI. However, significant variations in CA fragment yield (the ratio of the total CA fragment ion abundance to the abundance of the incident unfragmented ions) were observed. It is not clear from the results whether these variations reflect structurally different ions or ions of different internal energies. The CA spectra of [C 6 H 6 ] + ˙ ions derived from charge exchange reactions between the benzene dication and the target gases He, Ne, Ar, Kr and Xe have also been recorded and, once again, very similar fragment abundance patterns were observed along with large variations in total CA fragment yields. Charge exchange efficiency measurements are reported for reactions between the benzene dication and the targets He, Ne, Ar, Kr, Xe and C 6 H 6 (benzene) and also for the doubly charged ions derived from the linear C 6 H 6 isomers. In the latter case Xe and benzene targets were used. The energetics and efficiency measurements for the former reactions suggest that for targets such as He and Ne the processes probably involve excited states of the doubly charged ions. The efficiencies measured for the latter reactions were distinctly different for the three C 6 H 6 isomers and may indicate a strong dependence of charge exchange cross‐section on doubly charged ion structure.