Rutherford Back Scattering of Protons at Medium Energies

Abstract

In the 3-20 keV energy range for light ions we are on the threshold of validity for the Lindhard-Scharff theory, but the screening is sufficiently small for the screened Coulomb scattering to be approximated by Rutherford scattering. Using the Rutherford scattering cross section, McCracken and Freeman (1969) showed that, for an incident ion of energy E0 and atomic number Z1 upon a target of atomic number Z2,$$ where NE is the total number of back scattered ions with energy exceeding E, I(E/E0) is an integral which McCracken and Freeman plotted numerically in their paper, and the function f(z) is approximated by $$ for Z1 << Z2 For heavy targets the screening is not negligible and the expression (1) is only qualitative. However, it does predict the observed changes in NE with E0 to considerable accuracy, for energies in the several keV range.