Population of individual Ne 1s-1np Rydberg states measured across the 1s ionization threshold and the evolution of shake-up into shake-down

New high-resolution experimental results on Ne 1s near-threshold photoionization with subsequent decay into a 2p{sup 4}({sup 1}D{sub 2})n{sup '}p or 2p{sup 4}({sup 1}D{sub 2}){epsilon}{sup '}p state are presented. The population of Rydberg states up to n{sup '}=12 is determined as a function of excess energy. These data allow one to track in detail the transition from resonant Auger decay going along with shake-up of the spectator electron to shake-down and photoionization with recapture of the photoelectron. Results are in good agreement with a time-dependent quantum mechanical theory of Auger decay in the presence of a slow photoelectron.