Abstract
Following the semi-empirical approach of Khare (1969 and 1970) and Khare and Padalia (1970), the ionization cross section per unit energy range and the total ionization cross sections of CO2, CO, H2O, CH4 and NH3 due to electron impact ionization for energies varying from the ionization threshold up to 10 keV are calculated. The results are in fair agreement with the experimental data and other theoretical investigations.