ROLE OF SCATTERING-FACTOR ANISOTROPY IN ELECTRON, POSITRON, AND PHOTON HOLOGRAPHY

We have studied the angular anisotropy in the scattering factor of ele ctrons, positrons, and photons in solids. We show that as a function o f angle, the maximum number of dips in the scattering factor's magnitu de and jumps of near pi in its phase are related to the angular moment a of the bound and resonance states of the potential. The effect of th e scattering factor's anisotrogy on low-energy electron and positron h olographic wave-front reconstruction is discussed. Applying the variab le-axis small-cone method, a good-quality reconstructed image is only possible within angular regions where the scattering factor is near is otropic. Thus the usable window for low-energy electron wave-front rec onstruction is element dependent; the window size decreases as the ato mic number increases. Positrons, on the other hand, are like photons a nd are not bound by the potential. For positrons or photons, there is no elemental dependence of the usable window and the entire backscatte ring regime is suitable for holographic reconstruction. We have establ ished two rules that predict the maximum number of magnitude dips and phase jumps in the scattering factor for any element. [S0163-1829(98)0 6639-9].