Dynamics of oxygen Rydberg atom generation following O 1 s inner-shell excitation of H₂O

The emission of low-energy electrons from H₂O has been investigated at photon excitation energies in the vicinity of the O 1s ionization threshold. Neutral oxygen Rydberg atoms (O*) were found to form, and the correlation between the initial inner-shell excited state of H₂O and the Rydberg state of O* was determined. The initially excited electron in a Rydberg orbital is shown to remain associated with O* even after the cleavage of two O-H bonds. We also show that the energy discrepancy between two Rydberg states of H₂O and O* can be explained by the influence of the post-collision interaction, which becomes stronger as the excitation energy approaches the 1s ionization threshold.