Determination of bond ionicity using low-energyD+scattering

We report on the systematic investigation of neutralization of low-energy ${\mathrm{D}}^{+}$ ions scattered from 17 ionic-compound surfaces with particular emphasis on the relation between the neutralization probability of ${\mathrm{D}}^{+}$ and the ionicity of the surface atomic bonds. The ${\mathrm{D}}^{+}$ ions tend to survive neutralization provided that the target atom is completely ionized, whereas almost complete neutralization results if the target has covalent or metallic orbital hybridization with the ligand. The ${\mathrm{D}}^{+}$ spectra from nitrates, sulfates, and carbonates of Na and K, as well as ${\mathrm{K}}_2$ ${\mathrm{SiO}}_3$, exhibit surface peaks of ${\mathrm{D}}^{+}$ surviving neutralization for both cations and oxygen, indicating large ionicity in the alkali-metal–oxygen bond. Rather exceptional is ${\mathrm{Na}}_2$ ${\mathrm{SiO}}_3$, for which a relatively small ionicity is concluded from the absence of surface peaks. For the alkaline-earth compounds, ionicity decreases in going to the light elements as evidenced by the decrease of the surface-peak intensity. The occurrence of charge-exchange relaxation between cations and anions of ${\mathrm{NiSO}}_4$ and ${\mathrm{CuSO}}_4$ results in large neutralization probability of ${\mathrm{D}}^{+}$, while the closed-shell structures of ${\mathrm{Ag}}^{+}$ (4${\mathit{d}}^{10}$) and ${\mathrm{Pb}}^{2+}$ (6${\mathit{s}}^2$) in ${\mathrm{AgNO}}_3$ and Pb(${\mathrm{NO}}_3$ ${)}_2$, respectively, suppress neutralization to some extent so that the appreciable surface peaks appear.