Theoretical study on (e,2e) process for helium in perpendicular geometry
垂直入射几何条件下氦原子（e,2e）反应的理论研究

The triple differential cross section for electron impact ionization of helium in the perpendicular geometry is calculated by use of BBK model and modified BBK model. The results of the present work are compared with experimental data. The structure of the cross section is analysed and the exchange effects are discussed systematically.