Basis functions (normalized) used to construct the diabatic molecular wavefunctions.
The {A, B} denotes the spatially symmetric (singlet) combination (A_{1}B_{2 }+ A_{2}B_{1})(α_{1}β_{2 }- α_{2}β_{1}) where α, β are "up" and "down" spin functions and A, B are spatial MO's.

Singlet g-state

Singlet u-state

Chaudhuri PMC Physics B 2009 2:2 doi:10.1186/1754-0429-2-2