Multi-step post-collision interaction effects in K-shell photoionization of Kr

Yield spectra of multiply charged ions produced from cascade decays following K-shell photoionization of Kr have been measured in coincidence with threshold photoelectrons having near-zero kinetic energies (<0.05 eV). These observed yield spectra exhibit characteristic profiles of multi-step post-collision interaction effects induced by the cascades. Peak shifts of the profiles do not increase gradually along with the increase of the charged states, but bring about a step-like structure as a function of charge state. The step-like structure is due to the participation of radiative decays in the cascades following the K-shell photoionization.