Positive and negative hydrogen ions backscattered from Au, Ta, and ThO2 in the energy range up to 15 keV

Abstract

Samples of polycrystalline Au, Ta, and ThO₂ were bombarded by 5–15‐keV beams of H⁺₁, H⁺₂, H⁺₃, D⁺₁, and D⁺₃ ions. The backscattered positive and negative hydrogen ions were energy analyzed by a spherical condenser. For Au and Ta both the positive and the negative spectra start with zero intensity at zero energy and reach maxima, whose position depends on the primary energy and the ion species. For ThO₂ the positive spectrum is similar but the number of negative ions shows no maximum and is largest at energies below 1 keV and continues to decrease with increasing energy. With decreasing work functions of the target materials the number of backscattered negative ions increases. The ratio of negative‐to‐positive backscattered ions is larger than unity at low energies in the cases of Au and ThO₂. A comparison of proton and deuteron results shows that the ratio is equal for ions of equal velocities. For Ta and ThO₂ this ratio is considerably larger when the targets are bombarded with molecular ions as H⁺₂, H⁺₃, D⁺₂, and D⁺₃ than when bombarded with the corresponding atomic ions H⁺ and D⁺ with equal energies per atom.