Two-channel competition of autoionizing Rydberg states in an electric field - art. no. 053403

We present experimental data an the decay of xenon Stark states converging to the upper spin limit. In an electric field the Rydberg electron has two qualitatively different decay paths. if the electron changes the core state from the upper spin state into the lower spin state, it gains sufficient e nergy to escape the ionic core and autoionizes. Moreover, if the electronic state is above the saddle point, created by the electric field, it can fie ld ionize. The probability to autoionize is nearly constant around the sadd le point whereas the probability to field ionize rapidly increases above th e saddle point. With the velocity map imaging technique we monitor both ion ization channels as a function of (increasing) photoexcitation energy. We o bserve that the field ionization channel dominates the competition and gain s yield at the expense of the autoionization channel. The spectra are expla ined both with full quantum calculations and with a relatively simple descr iption for the overall behavior. These experiments show that the field ioni zation can be used in general as a clock for total core-dependent decay.