Dynamic screening of the (e, 2e) processes for low-energy electron impact ionization of helium

Based on the modified three-body Sommerfeld parameters, the effective shiel d of the residual electron in the final state of He+ is further modified fo r (e, 2e) processes. Such a modification represents a dynamic screening of the four bodies in the final state. The triple differential cross sections for electron impact ionization of atomic helium at an incident energy of 50 eV in the asymmetric geometry are calculated by use of the modified Sommer feld parameters. The results were compared with those of the absolute measu rements and the only existing theoretical results of the convergent colse-c oupling method. It tvas found that the present results give a better descri ption for the experimental data at fixed ejected energy of 10 eV.