Dynamics conditions for channeling during H− scattering on Cu(111)

The dynamics conditions for channeling effects during H− scattering on Cu(111) surfaces, including: critical angle, distance of closest approach to surface, reflective angle shift, energy loss, and channeling dip depth, are studied with Molecular Dynamics. Calculations show that the critical angle exponentially decreases with incident energy, and the distance of closest approach to surface decreases not only with the incident energy, but also with the incident angle. For the reflective angle shift and the energy loss, we find that there is a range of very small incident angles where both decrease slightly with the incident angle; beyond this range, they increase rapidly with both incident angle and incident energy. For large angles of incidence, the channeling dip depth exponentially increases with the incident angle. The H− ion injected through the middle point of two nearest neighbor Cu atoms on the first layer provides the maximum depth. The reason is a lower surface potential barrier for the injection through this point. The target atomic string density on the surface also affects the dynamics processes. Projecting along an atom string with higher atomic density, leads to a larger critical angle, a larger distance of closest approach to surface, a smaller reflective angle shift, a smaller energy loss, and a shallower channeling dip depth.