Pathways and reduced-dimension five-dimensional potential energy surface for the reactions H3+ + CO-->H2+HCO+ and H3+ + CO-->H2+HOC+.

To obtain theoretical insight regarding the stability and formation dynamics of the interstellar ions HCO(+) and HOC(+), stationary points and the associated vibrational frequencies on the full nine-dimensional potential energy surface for the electronic ground state have been calculated using coupled-cluster theory with both single and double substitutions (CCSD). The energetics were refined with a higher-level coupled-cluster method CCSD(T), with core-valence electron correlation treated at the complete basis set limit. To elucidate the formation mechanism and internal relaxation processes, the reaction paths for the reactions H(3) (+)+CO-->H(2)+HCO(+) and H(3) (+)+CO-->H(2)+HOC(+) were calculated at the second-order Moller-Plesset (MP2) level, and corresponding single-point energies were obtained at the higher CCSD(T)/aug-cc-pVTZ level. Based on the analysis of the main reaction processes, a reduced-dimension five-dimensional potential energy surface for this system was constructed from 128 440 ab initio points calculated at the CCSD(T)/aug-cc-pVTZ level.