Knowledge Bank

An ab initio approach is described for obtaining a quantitative description of the shapes of molecular potential curves. Emphasis is placed upon correlating all the orbital occupancies that lead to proper molecular dissociation. For the ground state of $O2$ the calculated energies of the first 10 vibrational levels above the bottom of the well are within 3 $cm-1$ of the experimental values while the first 22 levels are within 16 $cm-1$ of the experimental values. The importance of correlating non-bonding orbitals will be discussed. Application of the approach to several excited states of $O2$ will also be presented.