Exploring the Born Series with Ion-Atom Collisions

The work of Brandt and his co-workers focussed attention on corrections to the first Born approximation needed to reproduce experimentally measured low energy ionization cross sections. By varying the charge of the target nucleus ZN and the charge of the projectile, ZP, Brandt explored the Born series and introduced the concepts of increased binding, polarization, and Coulomb deflection. Another scheme for correcting the Born approximation is due to Glauber. This method has been applied to electron and proton scattering by Franco and his collaborators. The theoretical basis for both these pictures is reviewed in the light of accurate numerical calculations of excitation and ionization.