The diagonal born-oppenheimer correction for He2+ and F+H2

An unrestricted Hartree-Fock evaluation of the diagonal Born-Oppenheimer correction is reported. The correction is calculated for He2+ and F + H2 → FH + H. For He2+ it is found that on addition of the correction the mean deviation of the best theoretical transition energies is increased (when compared with experiment) by the same order of magnitude (0.04 cm−1) as the value of the previous mean deviation. The correction increases the barrier height for the F + H2 reaction by 0.04 kcal mol−1.