Coherence and correlation in electron impact autoionisation of neon and argon

The authors present experimental data on the autoionisation of neon and argon excited by electron impact. The energy of the incident electrons is chosen such that the two outgoing electrons in the final state have comparable energies. In this energy region state-state coherences and post-collision interactions (PCI) between the two electrons may be observed. Examples of observations of state-state interferences are presented and the effect of PCI in these experiments is discussed. A detailed analysis of the measurements is complicated due to the presence of overlapping neighbouring states.