Low-Energy Positron Diffraction from a Cu(111) Surface

Abstract

The first observation of low-energy positron diffraction from a solid surface is reported. Slow (20-400-eV) monochromatic positron beams were focused onto a Cu(111) surface and their elastically scattered distributions detected with a channel electron multiplier. Measurements of the scattered intensity versus angle as a function of incident energy show peaks at the predicted ($0\overline{1}$) and ($0\overline{2}$) diffraction angles. Profiles of intensity versus energy at fixed angles exhibit maxima corresponding to the primary Bragg peaks.