The correlation between molecular and atomic Rydberg levels

Abstract

The energies of the Rydberg states of H₂O relative to the ionization potential have been calculated starting from the energies of the Ne Rydberg states. The first step is the calculation of Ne valence state energies, the second is the calculation of first and second-order perturbations due to the change in the nuclear framework. These perturbation terms are sensitive to the form of the wave function of the Ne Rydberg orbitals. SCF wave functions have been chosen when available. There is a reasonable agreement between the calculated and observed energies except for the 3s states which are probably better correlated with a transition to an anti-bonding molecular orbital than a transition to a Rydberg orbital.