Evolution of the Post-Collision-Interaction Profile from the Resonant Auger Shakeup $/$Shakedown Lines at the Ionization Threshold

Xe ${4d}_{5/2}$ and Kr ${3d}_{5/2}$ Auger spectra were studied by scanning the photon energy across the corresponding ionization thresholds. Finest details in the development of the post-collision-interaction profile from the shakeup/shakedown lines were observed experimentally for the first time. The utilization of the resonant Auger Raman effect allowed one to resolve, with very high resolution, new intense fine structures besides the conventional $\mathrm{np}\to \mathrm{mp}$ shake transitions in the shake features. They were identified to be due to the transitions to the $\mathrm{ms}$ and $(m-1\mathrm{})d$ type final states.