Intermediate-Energy Positron and Electron Bremsstrahlung from Atoms

Using a relativistic partial-wave method we calculated numerically the photon energy-angle distributions for positron and electron bremsstrahlung in the field of atoms with atomic number Z = 1, 13, and 79 for kinetic energies of incident positrons or electrons T1 = 1.0, 2.0, and 2.5 MeV. In this intermediate-energy region, our studies indicate that the Born approximation predictions agree quite well with our partial-wave results for the shape of the photon energy-angle distribution of the positron bremsstrahlung. For high-Z elements, the Born approximation predictions are not good for the shape of the photon energy-angle distribution of electron bremsstrahlung. The Born approximation results can be improved if one multiplies by the Elwert-factor which is independent of photon angle. Our partial-wave results also indicate that the shape of the photon energy-angle distribution of positron or electron bremsstrahlung is almost independent of atomic-electron screening. PACS. 34.80.i – Electron scattering. PACS. 34.90.+q – Other topics in atomic and molecular collision processes and interactions. I