Near-threshold multielectronic effects in the Cu Kα_1,2 x-ray spectrum

The variation with excitation energy of the line shapes of the Cu Kα_1,2 x-ray spectrum was measured with high energy resolution near the K-shell threshold. Fits with ab initio Dirac-Fock calculated spectra allow us to estimate separately the magnitudes and energy variations of the 3d electron shakeup and shakeoff probabilities from threshold to saturation. The Thomas model is found to account well for the intensity evolution, in contrast with shakeoff from deeper shells. A suggested, yet unexplained, strong dependence of the shakeoff intensity saturation range on the shell number is confirmed.