NEUTRALIZATION OF LOW-ENERGY D+ SCATTERED FROM SOLID-SURFACES

In this study, some of the fundamental aspects of neutralization of low-energy (10300-eV) D+ ions have been addressed in comparison with that of He+ ions. To examine the role of the valence-band structure in determining neutralization rates for D+, a range of target materials has been studied (Mo, Ta, Ag, Pb, BaF2, CsCl, LiCl, AgCl, PbCl2, etc.). The surface peak of D+ is extremely small compared with that of He+ in scattering from metal surfaces, while the contrary is sometimes true in scattering from ionic compounds such as alkali-metal halides and alkaline-earth halides. It is found that the neutralization of D+ depends on the local electronic states of the target atom and occurs via the resonant neutralization by s- or d-band electrons of the metal atoms or via an energy-level-crossing mechanism between D 1s and the closed p band of the anions. The reason why the neutralization probability for D+ is very much enhanced compared with that for He+ is that the surface electronic state relevant to the resonant neutralization of D+ is not a level but a broad valence band (band effect). It is concluded that the smaller ionization energy of deuterium than helium results in strong coupling of the D 1s level with the valence band. © 1990 The American Physical Society.