The Molecular Effect in the Multiple Ionization of Diatom Molecules by Fast Ion Impact

The multiple ionization process is investigated for the molecular targets on the basis of the recently developed contracted independent electron model (CIEM), where the impact-parameter-dependent ionization probability plays a key role. We found that the multiple ionization cross sections strongly depend on the angle between the incident beam direction and the molecular axis. Also the molecular effect is found that the ionization cross section for a molecular target is not equal to the sum of those for the constituent isolated atoms. Moreover, we proved the sum rule on the net ionization cross section. Numerical estimation shows that the multiple ionization cross sections for N 2 and CO molecules, bombarded by the ions at the energies of more than 100 keV/u, are in better agreement with the experimental data than the other models.