Isotope Dependence in K, L and M Shell Ionization Cross Sections by ³He⁺ and ⁴He⁺ Bombardments

Abstract

The ionization cross sections of Al–K, Cu–L, Mo–L, Ag–L and W–M shells have been presented for the incident ³He⁺ and ⁴He⁺ ions in the energy range from 45 to 90 keV/amu. The cross sections have been evaluated from the experimentally obtained thick target yields of characteristic X-rays, referring to the semiempirical stopping power data of helium ions. Contrary to the prediction by Born approximation, isotope dependence has been clearly ascertained in the ionization of target atoms. The quantitative analysis for Al–K shell ionization has shown that the collision process can be explained by the “binding theory”. The isotope dependence is mainly attributed to the Coulomb deflection difference of the isotopic projectiles near the target nucleus.