A survey is given of the available cross-section data for ionization of inner-shell electrons by incident electrons in the range of interest for electron-probe microanalysis and for Auger-electron spectroscopy of solid surfaces. Owing to the paucity of data, the bulk of the discussion is limited to K-shell and L-shell ionization of light atoms. Calculated, semiempirical, and experimental cross-section data have been intercompared graphically and through fits to the linearized Bethe equation for inner-shell ionization (the Fano plot). Almost all of the data could be satisfactorily fitted over the range 4 <~ Unl <~ 30, where Unl=E0 / Enl, E0 is the incident electron energy, and Enl the binding energy of electrons in the nl shell. From these fits, values could be obtained of the "effective" Bethe parameters bnl and cnl. Values of the parameter bnl have also been derived from photoabsorption data and were found to be generally consistent with the ionization data if account was taken of the distribution of differential oscillator strength with respect to excitation energy and the consequent expected variation of bnl with incident electron energy. The derived "effective" Bethe parameters should not therefore be used outside the range of each fit.
Citation: Reviews of Modern Physics
Pub Type: Journals