Atomic inner-shell ionization.

Abstract

Cross sections for the K-shell ionization of medium-heavy atoms by relativistic electrons have been calculated in a relativistic framework in the Coulomb gauge to order ${\ensuremath{\alpha}}_{0}$ (=${e}^{2}$/\ensuremath{\Elzxh}c) in the interaction Hamiltonian. Here exchange is neglected. The incident- and scattered-electron wave functions are described by Dirac plane waves. Only the bound- and ejected-electron wave functions are described nonrelativistically for a screened Coulomb potential, used earlier by the present authors. Thus the screening effect is taken into account in this calculation in a satisfactory manner. The calculation is a repetition of what has been published recently by the present authors with one important exception: Here, the ejected-electron continuum state wave function that is used is determined variationally for the above screened Coulomb potential. Thereby some perturbation approximation of ad hoc nature could be avoided. As a consequence, considerable improvement is noticed in the total cross-section results. Comparison with experimental results for $^{29}\mathrm{Cu}$, $^{47}\mathrm{Ag}$, and $^{79}\mathrm{Au}$ shows a good agreement. The calculation may easily be extended to ionization from other shells.