Nascent Product-Vibrational State Distributions of Thermal Ion-Molecule Reactions Determined by Infrared Chemiluminescence

摘要

A flowing afterglow apparatus is used to study the dynamics of ion molecule reactions by detection of vibrational states in the products with infrared chemiluminescence. A number of simple proton transfer reactions have been studied, e.g. F(-) + HX yields HF(v) + X(-) (X = Cl, Br, I). The results show distinct differences from the analogous neutral reactions, F + HX yields (HF(v) + X, which are attributed to the long range attractive forces present in the ion reactions. The reaction of N(+) + O2 is studied and discussed with respect to atmospheric implications. Other reactions of polyatomic molecules have been studied to test whether the products are formed in a direct fashion or through a long lived collision intermediate. The reaction, H + SF6(-) yields HF(v) + SF5(-), is found to have a high degree of vibrational excitation, indicative of an early attractive energy release followed by a strong repulsive release. Associative detachment processes, F(-) + H, D yields HF(v), DF(v) + e, take place via the interaction of the negative ion HF potential curve and the neutral HF surface and produce exceptionally high amounts of vibrational excitation. The results are compared to successful theoretical models of Gauyacq, in which the electron is released by dynamically-induced transitions on the outer region of the potential upon the initial reagent approach. (Reprints)