Fast electron contribution in electronic stopping for p-He and p-Ar collisions

Our study has shown that in collisions p-He and p-Ar with energies above 50 keV fast electrons carry away as kinetic energy up to 70 % of energy released during particle stopping. Ignoring the fast electron contribution makes impossible bringing independently measured cross sections of elementary processes of ionization, exci-tation, stripping and charge exchange into compliance with measured cross sections of electronic stopping. Fast electron emission in collisions of energetic ions with solids may induce extra radiation effects (create additional vacancies and defects in solid).Mean kinetic energies of ejected electrons We obtained from the analysis of cross section ratio agree well with directly measured energy spectra of the emitted electrons. The dynamic ionization theory implies the We pro-portionality to initial velocity v. In the considered cases, such a dependence takes place at the velocities below 2 a.u. At higher velocities, the observed dependence is successfully described in the framework of the Born approximation.

Automated summary

Our study has demonstrated that in collisions of p-He and p-Ar with energies above 50 keV, fast electrons take away up to 70% of the energy released during particle stopping as kinetic energy. Neglecting the contribution of fast electrons makes it impossible to reconcile independently measured cross sections of ionization, excitation, stripping, and charge exchange with measured cross sections of electronic stopping. The mean kinetic energies of emitted electrons, obtained from the analysis of cross-section ratios, are well in agreement with directly measured energy spectra.