Investigation of Multi-ionization Processes of Kr and Xe Using Short-pulse X-rays and Time-of-flight Apparatus

The multi-ionization processes of Kr and Xe in the K-edge photon energy region were investigated using short-pulse x-rays and time-of-flight apparatus. The generation of Kr13+ ions in this photon energy region was observed for the first time. The distribution characteristics observed in the experiment, such as the production of Kr13+ ions, high production ratios of Kr4+, Kr5+, and Kr6+ ions, and the existence of a small peak for Kr8+, were quantitatively reproduced by the Monte Carlo simulation for the charge distribution of Kr ions following 1s of inner shell ionization. The highly charged ions were suppressed in the experiments compared with those in the simulation, probably owing to the inhibition of certain Coster-Kronig processes in the highly charged ions, which were not considered for analysis. The charge distribution of Xe ions following 1s of inner shell ionization was also investigated. A similar charge distribution was observed when the photon energy was located between the K and L edges. This is because the Xe 1s hole state mainly undergoes ultrafast relaxation to the 2p hole state owing to the strong dipole transition moment between the 1s and 2p states.