Evolution of beam-foil-excited Rydberg states on femtosecond time scales -art. no. 042708

Traditional. beam-foil methods for measuring lifetimes of low-lying atomic levels are generally impractical beyond Z similar to 35 because of the corr espondingly shorter flight times when lifetimes become less than a few tens of picoseconds. We recently reported the results of an experiment using a novel two-foil method to measure the 9.5-psec lifetime of the 2 P-3(2) leve l in heliumlike krypton. We describe hen the results of an extension of tha t work in which we measured the time evolution of the N greater than or equ al to 2 excited state population between the foils by observing the depende nce upon foil separation of the charge-state distributions emerging from th e second foil. The results are consistent with the well-known power-law dep endence of Rydberg-fed atomic transitions observed in beam-foil studies, bu t probe a much shorter time scale than has hitherto been accessible.