Post-collision interaction in electron-helium scattering

Abstract

It is pointed out that the so-called 'displaced threshold effect', recently reported by Hicks et al. (see abstr. A71444 of 1973) may lead to indirect excitation of atomic states under electron impact resulting in the occurrence of structures in the excitation curves. Experimental results on the excitation of helium by electron impact have been re-analysed and evidence is found that some structures indeed may be due to the proposed indirect excitation mechanism.