Abstract
The potential energy curves depending on the internuclear distance were carried out for the ground X-3 Sigma(-) and excited 1(1)Sigma(+)(g), 1(1) Delta, 1(3) Pi, 1(1) Pi, 2(3) Pi and 2(1) Pi electronic states of the O-2 molecule. Equilibrium distances R-e, oscillations frequencies omega(e) and the rotational constant B-e of the X-3 Sigma(-), 1(1)Sigma(+) and 1(1)Delta electronic states of the O-2 molecule, have been calculated via the complete active space self- consistent field CASSCF, which is followed by the valence internally contracted multireference configuration interaction MRCI (single and double excitation with Davidson correction) and CASPT2 methods in combination with several correlation-consistent basis sets. The comparison of these values to the theoretical and experimental results available in literature shows a very good agreement. While a summary of this information is presented, emphasis here is on the state of knowledge of the complex electronic structures which arise from the interaction between the Rydberg-Rydberg and Rydberg-valence states of both u and g symmetries.