Resonance enhancement of relativistic effects for the scattering of very slow electrons by heavy atoms

Polarization of scattered electrons is enhanced up to 1 near p- and d-wave resonances or weakly bound negative-ion energy levels (‖E‖≲0.1 eV, ${\mathit{v}}^2$/${\mathit{c}}^2$≲${10}^{\mathrm{-}6}$). We consider as examples Ra and Ba. We also note that the cross section for Ra is very large (>${10}^{11}$ b at electron energy ∼${10}^{\mathrm{-}2}$ eV).