Towards a perfect scattering experiment

It is now feasible to perform scattering experiments between spin-polarized electrons and state-selected target atoms where the scattered electrons are energy and spin-analyzed and the final atomic state also determined. Additional information may be obtained in the case of electron impact excitations, in which angular correlations between the scattered electrons and photons from the decay of the excited state are studied. These experiments will provide the most stringent test of theoretical models of atomic scattering because they will measure all quantum mechanical 'observables' in experiments in which interactions much weaker than coulombic are present. The approach towards such experiments is discussed. (orig.)