Relativistic Effects in Elastic Scattering of Electrons from Heavy Atoms

Relativistic effects in elastic scattering of electrons from heavy spinless atoms such as Hg are investigated for low energies. Charge cloud polarisation, electron exchange and absorption out of the elastic channel are taken into account. The comparison with experimental data shows that the Pauli approximation is in general not sufficient for a proper description of relativistic effects. The authors discuss the reasons for that and determine the region of validity. The relative importance of the various relativistic terms on spin-dependent observables is compared. In particular, the influence of terms of higher order than α ² on the observables is discussed, whereby it is illustrated why only the full relativistic theory gives a good agreement with experimental data.