Probing the Rydbergization of Water through the Stabilization Method

A molecular orbital or electronically excited state may change its character, from Rydberg or mixed valence-Rydberg to valence, as dissociation progresses. This geometrical dependency of the electronically excited states is known as Rydbergization. Recently, we proposed a new approach to characterizing the nature of electronically excited states based on the stabilization method [Randi P. A S, et al. J. Phys. Chem. A, 2025, 129, 5820-5828.]. Here, we demonstrate that the stabilization method can effectively describe the Rydbergization phenomenon in the low-lying excited states of water. To this end, we analyze both the symmetric and asymmetric dissociation pathways, comparing our findings to previously reported results whenever possible. In addition to reproducing established data, we present new insights into the symmetric dissociation of states with B ₂ symmetry, as well as previously unexplored behavior along the asymmetric dissociation pathway. We conclude also that Rydbergization is pathway-dependent and that conclusions drawn from one geometric distortion cannot be uncritically generalized to others.