Effect of vibrational excitation on the dynamics of ion molecule reactions

A technique of vibrational effects on ion molecule reaction cross sections is described. Vibrational and collision energy dependent cross sections are presented for proton and H atom transfer, charge transfer and collision induced dissociation reactions in various isotopic H2() + H2 systems. All the reactions are highly influenced by avoided crossings between the ground and first excited potential energy surfaces. Charge transfer between reagents as they approach each other, transition to and in some cases reactions on excited potential energy surfaces, competition between different channels, and strong coupling of proton and charge transfer channels which occurs only for two of the systems studied (H2() + Ar, N2) are discussed. Oscillatory structure in the collision energy dependence of the endoergic H2() (v = 0) + Ar charge transfer reaction for the first time is , and a simple model which is commonly used for atom-atom charge transfer is used to fit the peaks. A simple model is used to assess the importance of energy resonance and Franck-Condon effects on molecular charge transfer.