A method to obtain the crystal potential from the intensities of the diffracted beams in high-energy electron diffraction is proposed. It is based on a series of measurements for specific well determined orientations of the incident beam, which determine the moduli of all elements of the scattering matrix. Using unitarity and the specific form of the scattering matrix (including symmetries), an overdetermined set of non-linear equations is obtained from these data. Solution of these equations yields the required phase information and allows the determination of a (projected) crystal potential by inversion that is unique up to an arbitrary shift of the origin. The reconstruction of potentials from intensities is illustrated for two realistic examples, a {111} systematic row case in ZnS and a [110] zone-axis orientation in GaAs (both noncentrosymmetric crystals).

The authors report new differential cross section measurements (E0=1.5-50 eV) and coupled channel optical model calculations for elastic scattering of electrons from helium. The experimental results, from a crossed electron-atomic beam apparatus are analysed via a complex phaseshift technique with the derived phaseshifts, and their associated errors, then being used to derive total elastic, total reaction, total momentum transfer and grand total cross sections, and their respective errors, in a mathematically rigorous manner. Further, the authors applied fixed-energy inverse scattering techniques to the present data in order to deduce the interaction potential between the colliding particles.

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