Measurements on post-collision interaction in L-shell ionisation of Ar by electron impact at large excess energies

Abstract

The authors have measured the energy shift epsilon of the L3M1M23 (3P2) Auger line (Auger energy EA approximately=191 eV, level width Gamma (ArL3)=130 meV) at large excess energies in the energy region from E1=100 eV up to E1=10 keV with an experimental error of only +or-5 meV. This high precision was achieved using as reference line a neighbouring satellite line with a value of Gamma an order of magnitude smaller than Gamma (ArL3). The authors' experimental results are in full agreement with previous experiments on the post-collision interaction (PCI) shift epsilon in Ar L-shell ionisation but, due to the accuracy of the new data, their experiment reveals for the first time a precise functional dependence of the PCI shift epsilon on the excess energy E1 at large excess energies for electron impact ionisation. They observe that epsilon (E1) changes abruptly at E1 approximately=1 keV and remains constant for larger excess energies. This behaviour is not predicted by published theories. Recently, however, Sandner (1985) has indicated the existence of such a constant PCI shift at large E1.