ALIGNMENT AFTER INNER-SHELL IONIZATION BY ELECTRON-IMPACT NEAR AND ATTHRESHOLD

The alignment A20 of Ar+ (2p3/2(-1)), Mg+ (2p3/2(-1)) and of Zn+ (3d3/ 2(-1)) ions after electron impact ionization have been measured via th e angular distribution of Auger electrons and the linear polarization of fluorescence radiation for the range of impact energies E0 from sev eral times the threshold energy down to near or even to the threshold. The experimental results are compared to PWBA and DWBA values which a re available for Ar and Mg 2p3/2 ionization. From the alignment values obtained near or at threshold it is concluded that two-electron parti al waves with L = 0 and L > 0 (for Zn 3d3/2 ionization this can be spe cified up to L = 0,1,2) contribute to the Wannier threshold cross sect ion.