Observation of elastic scattering of positrons and electrons at glancing incidence

Elastic intensity versus energy ($I-V$) spectra have been observed using both positrons and electrons scattered at glancing incidence (83°-56° with respect to the surface normal) in the energy range of 50-450 eV from a variety of metallic and alkali-metal-halide surfaces. Unlike the electron spectra under the same conditions, all glancing-angle positron $I-V$ spectra have broad (≥100 eV) features. The enhanced broadening is associated with the reduced penetration depth of the elastically scattered positrons. Peak positions and widths fit a quasikinematic calculation of the intensity for Cu(100).