An evaluation of the exchange contribution in the scattering of electrons by positive ions

With an adaptation and modification of the approximations proposed by Ochkur in 1964 and Rudge in 1965, two approximations are derived to evaluate the T matrix which corresponds to the exchange process occurring in the collision between electrons and ions. The theory is applied to the calculation of the cross sections Q(³P -> ¹D) in the ground configuration of the ions N II, O III, S III, Cl IV and Ar v. The comparison with previous calculations made by Seaton in 1953 and Czyzak and Krueger in 1964 is satisfactory.