K-, L and M-shell ionization cross sections have been measured for 23 elements, 12≦Z≦92, after bombardment with relativistic electrons, 15≦E065MeV, by means of high resolution semiconductor detectors and a recently developed gas-scintillation proportional counter. For constant electron bombarding energy E0 the ionization cross sections follow a power law dependence, σ{reversed tilde}Z-α, and for E0=50MeV we deduced α =2.45±0.02 for the K shell and α=3.00 ±0.09 for the L shell. The observed Z dependence exhibits significant systematic deviations from theoretical predictions which exceed the experimental values up to 15 % at low Z elements for the K shell and on the average about 11% for the L and M shell. The same behaviour of too low experimental values, i.e. an overestimation by the theory, is observed for the energy dependence of the cross sections for all shells. A scaling behaviour describing the Z and E0 dependence for all K-, L and M-shell data points is observed which also predicts the experimental values by other groups at lower and higher energies correctly. The comparsion of the measured LΒ/Lα, and Lγ/Lα intensity ratios for high Z elements with the values obtained by other groups in the energy range 0.3≦E0≦1,000 MeV exhibits an increase with bombarding energy that cannot merely be explained by the energy dependence of the subshellionization cross sections for the L shell. An attempt to explain this effect with the change of the Coster-Kronig transition probability is described. © 1979 Springer-Verlag.
