CHARGE DIRECTED REACTIVITY - A SIMPLE ELECTRONIC MODEL, EXHIBITING SITE SELECTIVITY, FOR THE DISSOCIATION OF IONS

A Huckel-type effective Hamiltonian is used to examine the conditions for site-selected reactivity. The example is the dissociation of a pos itive ion, as in mass spectrometry. Coupling to the dissociative chann els is included by a rate operator. We examine the time evolution of t he charge and bond order matrices and of the yield of fragments follow ing a localized initial ionization. Dissociation is found to follow th e (positive) charge. Variations in the local properties can markedly c hange the dissociation pattern. A more statistical limit is reached wh en the migration of charge is unimpeded. (C) 1998 Elsevier Science B.V .