Theoretical study of the vertical electronic spectrum of O 2: Mixing of valence and Rydberg states

Abstract

All-valence-electron CM calculations are reported for a large number of electronic states of O 2 at the ground state equilibrium bond length. The configuration subspaces considered include all single and double excitations with respect to a series of the most important terms in the expansion of each state. The importance of the choice of such reference configurations as well as of the use of approximate natural orbitals in these calculations is discussed Mixing at Rydberg and valence states is observed in numerous cases and the significance of this phenomenon in the interpretation of the electrons spectrum of this system is considered.