G2 ab Initio Calculations on the F+ + OH2 Singlet and Triplet Potential Energy Surfaces

The Gaussian-2 (G2) theoretical procedure, based on ab initio molecular orbital theory, is used to study the potential energy surfaces corresponding to [H2O,F](+) singlet and triplet state cations which can be generated in the gas-phase reactions between F+(P-3) and F+(D-1) with water. Important differences between singlets and triplets, regarding both their bonding and their stabilities, have been found. The most outstanding result is that although the first D-1 excited state of F+ is about 2.6 eV above the P-3 ground state, the most stable product of the reaction between F+ and water corresponds to a singlet state cation, 1(S). This is so because, in general, triplet state cations are ion-dipole complexes, while the singlets are covalently bound species. Single charge transfer is the most likely process in F+ + water reactions. Very likely, this resonant charge transfer occurs into an excited state of OH2+, The formations of OH+, FH+, and O+ are also exothermic processes. The estimated heat of formation of the most stable H2OF+ species is 211.4 kcal/mol.