How to Explain the Difference between (?, e) and (e, 2e) Spectroscopic Factors

Abstract

It is shown that the relative line intensity of the main and satellite lines in the atomic shell ionisation spectrum depends significantly on the mechanism responsible for the removal of the electron. This dependence is explained by the influence of many-electron correlations in the initial state of the atom to be ionised, which is considerable when the momentum transferred to the ion is large. This is the case for photoionisation, i.e. the (y, e) reaction under the condition of large photon energy. On the contrary, in electron momentum spectroscopy, such as the symmetric noncoplanar (e, 2e) reaction, the momentum transferred to the ion is typically small and the initial atomic state correlations are negligible. It follows from this that the spectroscopic factors of the different final states of the ion, as defined in the usual way, can be measured only for the (e,2e) reaction, whereas a more involved interpretation is necessary for the (y, e) reaction. Comparison of the calculated spectroscopic factors of Ar II and Xe II 2S ion eigenstates with recent (Y,e) and (e,2e) experimental data has confirmed this conclusion.