Collisions with Au(111) Surfaces*

In this study, we use a wave-packet propagation approach to investigates the H^- ion survival probability after collisions with Au(111) surfaces, for various incident ion energies and a wide range of exit angles, from 20⁰ to 90⁰ measured from surface. For all energies from 200 eV to 15 keV, the ion survival versus the exit angle exhibits a well-defined peak at low angles, followed by a broad structure at high angles. As the energy decreases, the peak gradually shifts to higher angles, and becomes wider. The ion survival mostly decreases with energy, as expected, except for energies below 2 keV, when it starts increasing significantly. The peak is attributed to the H^- projectile experiencing the effect of the Au(111) s-p energy gap, located between 1.95 eV and 6.55 eV, below the vacuum level. The band gap effect is fully experienced at lower ion energies and lower exit angles, and it strongly affects the survival probability. On the contrary, at high energies and large exit angles, the projectile does not feel the band gap anymore, and the Au(111) surface behaves like a jellium. This is fundamental research with a broad range of applications, such as in: Space Science, Plasma-Wall Interactions, Ion Collisions, Catalysis, Corrosion, and STM.