On the relevance of the final ionic state to the (e, 2e) TDCS

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Abstract
The He II n=2 satellite in the He ionisation spectrum is investigated by measuring the angular dependence of the (e, 2e) triple differential cross section (TDCS) in asymmetric geometry for the first time, at moderate momentum transfer (0.8 a-10) and low ejected electron energy (20 eV). The generalised oscillator strengths for the transitions to the n=1 and n=2 He II states are derived from the TDCS and their ratio is in fair agreement with a recent close-coupling calculation. The experimental angular distribution of the n=2 TDCS shows peculiarities, typical of continuum final-state correlations, which appear to be much more relevant when the final ionic state is the excited one.