Electronic Structure of Simple Homonuclear Diatomic Molecules I. Oxygen Molecule

Abstract

The wave functions of the ground state and several lower excited states of O 2 and O 2 + are calculated non-empirically at R =2.3 a.u. by LCAO MO method, where all sixteen electrons are taken into consideration and Slater type 1 s , 2 s , and 2 p atomic orbitals are used. For the ground state of O 2 , various approximate treatments are investigated. Further for 1 Δ g , 1 ∑ g + , 1 ∑ u - , 3 ∑ u + , and 3 ∑ u - states improved calculations are performed by mixing several configurations. By using the wave functions thus obtained, dissociation energy D e , excitation energies Δ E , molecular quadrupole moment Q , magnetic hyperfine structure parameters <ψ 2 (0)> and < P 2 / r 3 >, oscillator strengths f , diamagnetic second order Zeeman term χ dia , and polarizabilities α // and α ⊥ are calculated and compared with the observed values. The results are found to be improved appreciably by mixing a small number of configurations. Finally, several of the wave functions of the O 2 ground state are analyzed by the population analysis method developed by Mulliken.