Relativistic (e,2e) processes on atomic inner shells

The investigation of electron impact ionization by the electron-electron (e,2e) coincidence technique has been restricted to the nonrelativistic energy region (typically 10 eV to 10 keV). The authors report on an (e,2e) experiment using a 500 keV electron beam impinging upon thin-foil targets. Absolute triply differential cross sections and angular distributions for K-shell ionization of silver and gold were measured, showing appreciable discrepancies compared with theoretical predictions.