Z3effect in the ionization cross section of argon by 1.2- and 2.0-MeVαparticles

Abstract

The $Z^3$ correction to the differential cross section for ejection of electrons from argon by $\alpha$ particles is estimated by adapting the theory of Ashley, Ritchie, and Brandt for the $Z^3$ effect on stopping power. Results are compared with the difference between cross sections for ionization by $\alpha$ particles and equivalentvelocity protons. For ejected electron energies between 40 and 190 eV, good agreement is obtained between the model and experiment. The model predicts a significant enhancement of the cross section for ejection of low-energy electrons by $\alpha$ particles which is not observed.