What is the Bond Dissociation Energy of the Vanadium Hydride Cation?

Recent electronic state-selected measurements of the reactions of atomic vanadium cations with D₂ and CO₂ are reanalyzed to properly account for the kinetic energy distribution of the reactant neutrals. The need for this is demonstrated in the present work by comparing the D₂ data to that obtained previously in earlier experiments but unpublished. It is shown that the earlier data, which utilized a surface ionization source of V⁺, and the state-selected data for V⁺(a⁵D₂) are essentially identical in the threshold regions where they overlap. Differences in the electronic state energies and kinetic energy distributions of V⁺ in the two experiments are very small and much smaller than the kinetic energy distribution of the neutral reactant, which is identical in both experiments. It is shown that properly accounting for the latter distribution alters the conclusions regarding the threshold energy for the endothermic formation of VD⁺ such that recent conclusions regarding the bond energy of VD⁺ are substantially altered and found to reproduce the original bond energy determination. Accounting for all experiments, a revised best value for D₀(VH⁺) is 2.07 ± 0.09 eV [or D₀(VD⁺) = 2.10 ± 0.09 eV]. This conclusion is validated by high-level ab initio calculations. Differences in the new and older data sets for the V⁺ + D₂ reaction at higher energies (above the onset for dissociation of the product ion) are also discussed. The same methodology is then applied to recent studies on the state-selected V⁺ + CO₂ reaction.