Isotope Dependence in K, L and M Shell Ionization Cross Sections by Proton and Deuteron Bombardments

Abstract

The ionization cross sections of Al–K, Ti–K, Cu–L, Mo–L, Ag–L and W–M shells have been presented for the incident protons and deuterons in the energy range from 90 to 180 keV/amu. The cross sections are derived from the thick target yields of the respective characteristic X-rays. In contrast with the prediction by Born approximation, isotope dependence is clearly found in the ionization of each target atom. The cross section ratios for K and L shells against the projectile energy per nucleon line up systematically according to the shell binding energies of target atoms. The magnitudes of the K shell ionization cross sections are in good agreement with “binding theory” of Brandt et al.. This means that, in the present energy range, the ionization cross sections depend strongly on the Coulomb deflection of the incident particle and the transient additional binding energy of the K shell electron with the incident particle during the collision.