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Abstract
The relaxation processes in atomic xenon following core ionization of the 4𝑑 and 4𝑝 subshells by extreme ultraviolet (XUV) pulses from a free-electron laser (FLASH) are investigated using ion time-of-flight spectroscopy. We compare the dynamics following ionization and Auger-Meitner decays at 90-eV photon energy, i.e., near the giant resonance, with those at 160 eV, near the Cooper minimum, where cross sections for photoionization of the 4𝑑 and 4𝑝 subshells are similar. Final states with charges higher than 4 show signatures of sequential absorption of two XUV photons, followed by subsequent Auger-Meitner decay. The averaged lifetimes of some important excited states are measured in a two-color XUV-pump–near-infrared-probe experiment. A transient enhancement in the ion yield of Xe5+ with an average lifetime of (49±3) fs is obtained, attributed to transient intermediate states following the decay of 4𝑑 double-core-hole states.