Doubly differential positron-backscattering yields

Direct measurements of doubly differential (angle and energy) distributions of backscattered positrons are reported using an electro- statically guided slow-positron beam. Backscattering yields for 35-keV positrons incident normally on the target were measured as a function of both scattering angle {θ} and target atomic number Z(4{≤}Z{≤}82). Absolute backscattering coefficients for positrons are compared to previous measurements and to corresponding values for electrons. Some apparent inconsistencies among various data are shown to arise from the dependence of the backscattering yield on incident angle.