The unimolecular loss of HF by simple inorganic ions: a computational Dynamic Reaction Path study

The metastable dissociations of a series of simple inorganic gaseous ions o f general formula (H,F,M)(+), including NF3H+ (M = NF2), N2F2H+ (M = FN2), F2NOH2+ (M = FNOH) and FNOH+ (M = NO) have been investigated using classica l dynamics in order to rationalise their mass-analysed ion kinetic energy ( MIKE) spectra which, from earlier experimental studies, showed the systemat ic loss of neutral hydrofluoric acid, HF, accompanied by a fairly large rel ease of translational energy (T), All the simulations were initiated in cor respondence of the transition structures involved in the above decompositio ns and expanded on the related Hartree-Fock potential energy surfaces, calc ulated "on the fly" during the evolution of the trajectories according to t he Dynamic Reaction Path methodology. The initial associated momenta were d educed by performing a standard kinetic analysis of the above dissociations taking into account the specific features of the MIKE experiments. For all the above ions, the resulting computed Ts are in reasonable agreement with the experimental values, In addition, from a more accurate analysis of the trajectories, it could be possible to appreciate qualitatively both the sp ecific role of the internal degrees of freedom of the decomposing ions and the dynamic and energetic influence of the HF-M+ ion-neutral complex locate d between the dissociation products and the tight transition structure invo lved in the above decompositions.