A definitive analysis of the Rydberg and valence anti-bonding character of states in the O K-edge of H2O

Contour plots of the 4a1 and 2b2 orbitals are shown below. The changes of sign of ϕ between the O and H atoms graphically show O-H anti-bonding character. The orbitals extend well beyond the molecular centers illustrating contributions of Rydberg character.