No abstract

The 70eV electron ionization mass spectra of polycyclic aromatic compounds are characterized by the presence of relatively stable multiply charged molecular iolls m]"+ (n=24). When generated from the compounds benzene, napthalene, anthracene, phenanthrene, 2,3-benzanthracene, 1,2-benzanthracene, chrysene, 9,lO-benzopbenanthrene and pyrene, the relative abundances of the multiply charged ions increase dramatically with the number of Mgs. These compounds form multiply charged molecular ions

No abstract

No abstract

No 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.

No abstract

No abstract