A theoretical study of the binding and electronic spectrum of the Mo2 molecule

Multiconfigurational SCF and second-order perturbation theory have been employed to study seven low-lying singlet and triplet electronic states of the Mo2 molecule. The bond order of the ground state has been analyzed based on the effective bond order (EBO), indicating that a fully developed sextuple bond is formed between the two Mo atoms. The experimentally observed excited states a3Σu+ and A1Σu+ have been determined and the so-called 3Λ excited state identified as the b3Σu+ state, in agreement with experimental expectations.