An optical potential method for elastic electron and positron scattering from argon

We present the results of a complex ab initio optical potential calculation of elastic electron and positron scattering from argon atoms. The inclusion of the absorption part of this potential markedly improves the agreement of our results with experimental measurements. Most notably, the differential cross section for electron scattering is reduced in the mid-angular range while for positron scattering the shape of the differential cross section is substantially altered to conform to that found in experimental measurements. We have also investigated in detail the three critical minima occurring in the electron differential cross sections. While there is substantial agreement in the location of the two critical minima at lower energies, the location of the high-energy minimum remains unresolved.