Dissociation and recapture dynamics in H₂O following O 1s inner-shell excitation

The emission of low-energy and Auger electrons from H₂O has been investigated following photo-excitation/ionization at photon excitation energies just below and just above the O 1s ionization threshold. It is found that neutral oxygen atoms in high Rydberg states are formed. Direct evidence of post-collision interaction (PCI) between the Auger electron and the photo-electron is observed. The initially-excited electron is captured into a Rydberg orbital of H₂O⁺ and remains associated with the oxygen fragment even after the cleavage of both O-H bonds. This implies that the Rydberg states are stable, with the electron behaving as a spectator during the dissociation of H₂O⁺.