Alignment after inner-shell ionization by electron impact near and at threshold

The alignment A20 of Ar+ (2p32−1), Mg+ (2p32−1) and of Zn+ (3d32−1) ions after electron impact ionization have been measured via the angular distribution of Auger electrons and the linear polarization of fluorescence radiation for the range of impact energies E0 from several times the threshold energy down to near or even to the threshold. The experimental results are compared to PWBA and DWBA values which are available for Ar and Mg 2p32 ionization. From the alignment values obtained near or at threshold it is concluded that two-electron partial waves with L = 0 and L > 0 (for Zn 3d32 ionization this can be specified up to L = 0,1,2) contribute to the Wannier threshold cross section.