Abstract Experimental H− ion fractions measured after H− scattering from Ag(111) and polycrystalline Ag at 1 keV incident energy in specular conditions revealed a larger ion fraction on H−/Ag(111) compared to polycrystalline Ag for exit angles less than 100 measured from surface, while a smaller ion fraction has been obtained on H−/Ag(111) compared to polycrystalline Ag for exit angles larger than 100. The H− ion fractions on Ag(111) are calculated with the Wave Packet Propagation method adapted to ion-surface interactions. The calculated ion fractions nicely reproduce the experimental results. A detailed study based on the analysis of the projected density of states for various ion-surface distances, the ion's interaction time with the surface, and the ion's distance of closest approach to surface, explains the behavior of ion fractions on Ag(111) and polycrystalline Ag at small and large exit angles. At small angles, the effect of a larger distance of closest approach dominate over the ion's interaction time with the surface. This translates into less ion decay on Ag(111), because the states correlated asymptotically with H− and the surface state do not fully go through their avoided crossing and are mostly located inside the band gap. At larger angles, the ion is getting closer to the surface and the two states fully go through the avoided crossing. The state correlated asymptotically with H− moves into the image states energy region, while the state correlated asymptotically with the surface state approaches the bottom of the band gap. The electron loss is significant, and translates into a reduced ion survival on Ag(111).

中文翻译：

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从 Ag(111) 和多晶 Ag 散射的 H− 离子部分

摘要 在镜面反射条件下以 1 keV 入射能量从 Ag(111) 和多晶 Ag 散射 H− 后测量的实验 H− 离子分数显示，与出射角小于 100 的多晶 Ag 相比，H−/Ag(111) 上的离子分数更大从表面测量，而对于大于 100 的出射角，H-/Ag(111) 上的离子分数比多晶 Ag 获得的离子分数要小。 Ag(111) 上的 H-离子分数是用波包传播方法计算的离子表面相互作用。计算出的离子分数很好地再现了实验结果。基于对各种离子-表面距离的投影状态密度、离子与表面的相互作用时间以及离子最接近表面的距离的分析的详细研究，解释了离子分数在小出射角和大出射角下 Ag(111) 和多晶 Ag 的行为。在小角度下，较大距离的最近接近的影响在离子与表面的相互作用时间中占主导地位。这转化为 Ag(111) 上更少的离子衰减，因为与 H− 渐近相关的状态和表面状态没有完全通过它们避免的交叉并且大部分位于带隙内。在更大的角度，离子越来越接近表面，两种状态完全通过避免的交叉。与 H- 渐近相关的状态进入图像态能量区域，而与表面状态渐近相关的状态接近带隙的底部。电子损失是显着的，并转化为减少的离子在 Ag(111) 上的存活率。