Determination of complex scattering amplitudes in low-energy elastic electron-sodium scattering

Measurements of spin-resolved elastic electron-sodium scattering have been carried out at incident energies of 4.1 and 12.1 eV, and the ratio of triplet to singlet scattering cross sections has been obtained at each energy. The ratio is used to provide a determination of not only the magnitudes of the triplet and singlet amplitudes, but also the cosine of the relative phase difference between them. These determinations of magnitude and relative phase represent the most detailed characterization to date of electron-atom scattering from a ``one-electron'' target.