Double KL ionization in Al, Ca, and Co targets bombarded by low-energy electrons

The cross sections for the production of double K and L vacancy states in Al, Ca, and Co as a result of electron bombardment were determined for impact energies ranging from the double excitation threshold up to 20 keV. The cross sections were derived from the measured intensity ratios I_KαL⁽¹⁾:I_{KαL⁽⁰⁾} of the satellite-to-parent-diagram x-ray lines. The specific contributions of the shake and two-step electron-electron processes could be probed by comparing the relative satellite yields observed in the electron-induced spectra to those obtained by photoionization. In particular the energy-dependent cross sections for double K and L excitation resulting from two-step-two processes could be deduced. The measurements were performed by means of high-resolution x-ray spectroscopy, using a reflection-type bent crystal spectrometer.