Inner-shell spectroscopy: An atomic view

The motivation behind the development of inner-shell electron spectroscopies is to provide techniques for microelemental analysis. This requires that the ionization edges are atomic in form and that atomic cross-sections can be used. The basic atomic theory for inner-shell ionization by fast electrons is reviewed and applied to the calculation of edge shapes in electron energy loss spectroscopy as well as to calculation of partial and total cross-sections for quantitative analysis. The use of purely atomic theories to describe white line features due to excitation to unfilled bound states is also discussed. Finally a brief outline is given of those areas in which the atomic view fails, due to either diffraction effects of the fast electron or scattering of the low-energy ejected electron.