Resonances and Many-Body Effects in Electron Impact Excited Soft X-Ray Spectra

We present a brief review of variations of bremsstrahlung and characteristic soft X-ray emission yields near core level excitation thresholds in metallic La (4 f -metals) and the 3 d -metals treated by the author in collaboration with Wendin. We extend the discussion in this paper to include processes neglected in the above mentioned earlier work, the emphases being laid on the relative importance of resonant bremsstrahlung (fluorescence) versus characteristic emission and the importance of localised states versus extended states, for different core level excitation thresholds.