A study of photoelectron recapture due to post-collision interaction in Ne at the 1s photoionization threshold

Electron spectra from radiationless decay of a Ne 1s vacancy are measured with excitation energies immediately at the 1s ionization threshold. Special attention is given to the excess energy region where Γ is the lifetime width of the 1s vacancy. Spectra are dominated by recapture of photoelectrons into Rydberg states of Ne⁺ above the threshold, and by a smooth transition into the spectator resonant Auger spectrum below the threshold. High resolution of the present experiment allowed us to clearly observe Rydberg states up to n ≤ 8 and to determine the individual probabilities for populating of these states by photoelectron recapture. Results are compared with calculations based on the semiclassical theory of post-collision interaction extended to high Rydberg excitations of the primary photoexcited electron, as well as with a non-stationary quantum mechanical theory of near-threshold photoionization with subsequent Auger decay.