Ab initio potential functions for the ionic states of OH

Potential curves of the OH molecule correlating to the four lowest energy dissociation limits O(P-3)+H(S-2), O(D-1)+H(S-2), O(S-1)+H(S-2), O-(P-2)+H+ have been computed at the CI/CASSCF level with the AUG-cc-pVTZ basis sets with a special emphasis on the ion-pair states 3 (2) Pi and C (2) Sigma(+). A balanced treatment of the excited state potentials is achieved by using the state-averaging MO optimization procedure. The X (1) Sigma(+) and (1) Pi potentials of OH- have been also considered. After empirical correction of the errors at the dissociation limits, the computed functions are recommended for the future use in the diatomics-in-molecules studies of the structure and dynamics of oxygen/hydrogen containing molecular systems. (C) 1997 Elsevier Science B.V.