Abstract
Polycrystalline Nb samples were bombarded by 3–15‐keV proton beams at normal incidence. The energy and angular distributions of backscattered positively and negatively charged particles were measured quantitatively. By means of the charged fractions measured previously, the energy and angular distributions of the total number of backscattered particles including the neutrals were obtained. Integration of the distributions over all energies and angles yield the total reflection coefficients. These are considerably lower than existing theoretical values.