Application of classical collision theory to electron impact double ionization of atoms

The classical binary encounter theory in its symmetrical form has been applied to the double ionization of He and Li + . Process of double ionization has been assumed to proceed via double encounter. In both encounters correct quantum mechanical velocity distributions for the bound electron have been used. The results are compared with experimental observations and earlier calculations by Gryzinski's method. It is concluded that the single encounter model suggested by Mittleman (1966) is not entirely correct and substantial contributions are made by double encounter process.