Why the Lower-Energy Term of Singlet Dioxygen Has a Doubly Occupied π∗ Orbital.

The article discusses the study regarding the lower-energy term of singlet dioxygen which has doubly occupied the π* orbital. A physical examination for the relative energies of the lowest two singlet terms of dioxygen is presented by the study. Such explanation invokes certain molecular orbitals, which are eigenfunctions of orbital angular momentum about the molecular axis, including π+ and π-. Although π+ and π- are not commonly used than πx and πy, the latter are inappropriate for situations in which orbital angular momentum is considered.