Coulomb effects on the electron scattering radiation tail

We carry out a distorted wave calculation of the radiation tail accompanying relativistic elastic electron scattering from the atomic nucleus using recently developed techniques for evaluating the radial matrix elements entering the calculation. The difficulty of calculating the high multipole components of the bremsstrahlung cross section is avoided by introducing a distortion factor that can be evaluated within the required accuracy with about 20 photon multipoles. The calculation still requires extensive computational time, so we compare our distorted wave results to an ad hoc technique of including distortion in the Bethe-Heitler result that is widely used. Surprisingly, we find that the ad hoc technique is very good for energy losses less than about 70% of the incident electron energy.