Abstract: A theoretical method called multiple-scattering expansion was proposed and developed by author in the previous works^[1].This method has a few advantages, such as,high accuracy, simplicity for calculations and wide valid region. This method has been applied to calculations for the impact ionization cross sections of H-atoms, and the results are in agreement with the experimental data very well^[2]. A detailed description for practical calculations based on this method is given in the present paper.

Key words: electron-atom collision, ionization cross section