Carbon atom electron-impact double ionization

Scaling factors are introduced for the electron-impact excitation and ionization cross sections obtained in the distorted wave (DW) approximation. It is shown that the scaled DW cross sections provide good agreement with measurements for the single ionization of the C atom and C1+ ion.

The direct double-ionization (DDI) process is studied using a multi-step approach. Ionization-ionization, excitation-ionization-ionization, and ionization-excitation-ionization branches are analyzed. It is demonstrated that the three-step processes contribute 40% of the total DDI cross sections for the case where one of the electrons takes all of the excess energy after the first ionization process.