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Triple-differential cross sections (TDCS) are measured in a coplanar symmetric energy sharing geometry for a neon target. The experiments were carried out for ionization of the 2p orbital between 500 and 65 eV incident energy and of the 2s orbital at 226.9 and 126.9 eV incident energy. The main difference compared to helium target is the apparition of a structure at 85 degrees for ionization from both orbitals. This structure, clearly seen at 65 eV for the 2p shell, is enhanced as the incident energy decreases. Distorted-wave Born approximation (DWBA) calculations including post-collisional interactions (PCI) and polarization are compared with experimental data. This theoretical model is found to give quite a good fit above 200 eV incident energy for ionization of the 2p shell and from 126.9 to 226.9 eV for ionization of the 2s. Below 100 eV, some disagreement between theory and experiment is observed. Calculations in this energy region, nevertheless, enable the effects of target orbital polarization to be identified.

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We report on (e, 2e) experiments for excitation-ionization of helium made in asymmetric geometry at intermediate incident energy and low momentum transfer. The results are compared with Born 1 calculations. Some degree of agreement is obtained and seems to be improved by correction for post-collision interactions. But it cannot be expected that such simple models will correctly reproduce processes that depend so strongly on correlations.