Calculation of Electron Impact Ionization Cross Sections

The Gryzinski theory for electron impact ionization cross sections for atoms is examined with regard to the shape of the total ionization efficiency curve, the retotive importance of the contribution to the total cross section of inner electron shells, and agreement with experimental data. The theory agrees well with the available data. The reasons for the systematic differences of the predictions of this theory from those of Otvos and Stevenson are analyzed. Calculations are made for some diatomic molecules. The ratio of the calculated molecular cross section to the sum of the atomic cross sections varies from 0.8 to 1.3. The reasons for this variation are examined.