Relative cross sections and appearance energies in electron impact ionization and dissociation of mono-halogenated biphenyls

Abstract

A combined theoretical and experimental study on the fragmentation of the mono-halogenated biphenyls; 2-chlorobiphenyl, 2-bromobiphenyl and 2-iodobiphenyl upon electron impact is presented. The appearance energies of the fragments observed and the energy dependence of their relative cross sections are reported. This is a follow up on our previous report (Barclay et al., 2019) [24] on the influence of the dihedral angle on the ionization energy of these compounds, but here we report the appearance energies and the energy dependence of the relative cross-section for all the major fragments. The appearance energies are compared to quantum mechanical threshold calculations at the coupled cluster level of theory and possible molecular structures and reaction pathways are discussed for the observed m/z ratios. For the loss of the halogen along with 1–2 H the agreement between the experiment and theory is good as reported earlier. However, the discrepancy is considerably larger for the ring rupture channels.