Theoretical and experimental investigation of the triple-differential cross sections for electron-impact ionization of Kr(4p) and Xe(5p) at 1-keV impact energy

The triple-differential cross sections for the ionization of $\mathrm{Kr}(4p)$ and $\mathrm{Xe}(5p)$ by a fast electron where the exiting electrons have energies of 20 eV and 1 keV have been measured and compared with distorted-wave Born calculations. Difficulties were encountered when trying to place the relative data on an absolute scale by extrapolation to the optical limit: an extensive study of this normalization process is presented and it is argued that it is not applicable to the heavier atoms considered here, but can be used effectively for helium targets.