Electron correlation during photoionizaton and relaxation ofpotassium and argon after K-shell photoexcitation

We have measured the charge-state distributions of argon and potassium after ionization by photons with energies near the K-shell ionization threshold. Despite the similarity in core electron configurations, the two atoms show remarkable differences in the resulting distribution of ion charge states. The valence electron in potassium is rarely a spectator during core relaxation, and its presence enhances the loss of electrons excited into Rydberg levels or strongly reduces the recapture of slow photoelectrons during post collision interaction.