A structural investigation of [C₆H₆]²⁺ and [C₆H₆]⁺˙ ions involved in charge exchange reactions

Abstract

Mass-analysed ion kinetic energy spectra for collisional activation (CA) of [CSH,]+' formed via electron capture by [CSH,]" ions in collision with neutral benzene molecules have been compared for the CSH, isomers benzene, 1,5-hexedjae and 2,4-hexadiyne. Comparisons of fragment abnndPnce and total CA fragment yields were also made for [CSH,]+' 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 simidar 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 dear &om the results whether these variations reflect structurally dmerent ions or ions of merent internal energies. The CA spectra of [C6€&]+* ions derived from charge exchange reactions between the benzene dieation 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 & (benzene) and also for the doubly charged ions derived from the linear CSH, 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 Werent for the three CSH, isomers and may indicate a strong dependence of charge exchange cross-section on doubly charged ion structure.

Production of Long-Lived Benzene Dications from Electron Impact in the 20–2000 eV Energy Range Combined with the Search for Global Minimum Structures

“…Additionally, in general, ions with different internal energies may lead to different rates for the reaction pathways, producing different yields, but similar patterns. 82 Among all data sets, only two allow a comparison with the present results concerning the double-to-single parent ion formation, one electron impact experiment (ref A), 9 and one charge stripping experiment (ref E), 79 with the result that only the order of magnitude agrees reasonably well. However, the information, although limited, shows that there is rather high dispersion between the ratios of the dications in the 2E spectra compared to those of doubly charged ions in the traditional mass spectra (EI−CE) between the present EI and EI data available in the literature and less between 2E spectra data (CE−CE).…”

“…Here, the open question is if the doubly charged molecular ions produced in the source and measured via the CE process are similar to the molecular dications formed by direct ionization ,, because of the strong molecular structural changes in the CE process. Correlations are, however, not so straightforward.…”

“…For this to be true, it is necessary for all doubly charged ions to have the same cross section for CE. Additionally, in general, ions with different internal energies may lead to different rates for the reaction pathways, producing different yields, but similar patterns …”

Dissociation of Benzene Dication [C6H6]2+: Exploring the Potential Energy Surface

“…The Coulomb explosion of benzene is particularly interesting and has been studied extensively because of its high symmetry and diversity of dissociation pathways. − The dissociation of benzene was studied, and its cation appearance energy was determined as early as 1938 by Hurstulid and co-workers . Guilhaus et al studied the [C 6 H 6 ] + . ions formed via electron capture (EC) by [C 6 H 6 ] 2+ and compared it to [C 6 H 6 ] + .…”

“…[27][28][29][30][31][32][33][34][35][36][37] The dissociation of benzene was studied, and its cation appearance energy was determined as early as 1938 by Hurstulid and co-workers. 38 Guilhaus et al 39 studied the [C 6 H 6 ] +. ions formed via electron capture (EC) by [C 6 H 6 ] 2+ and compared it to [C 6 H 6 ] +.…”