Further data on the post-collision interaction in electron scattering by helium

A series of measurements in the 'constant energy loss' mode has been carried out by means of a high-resolution electron spectrometer, at a collection angle of 2 degrees . The features observed in excitation functions by the Manchester group, and described by the 'shake-down' model, appear consistently at energy losses both above and below the ionisation threshold. The authors' analysis confirms that these features are caused by the detection of ejected electrons. This interpretation is supported by ejected-electron spectra measured in the 'constant incident energy' mode. The energy changes involved in the post-collision interaction have been plotted as a function of the energy excess of the exciting electrons, in comparison with the data of Spence (1975) and of Smith et al. (1974).