Optical excitation of he projectiles during reflection at a monocrystalline surface under channeling conditions

Abstract The emission of visible light from 195 keV He projectile ions excited by grazing scattering at a (101)Ni surface is used to perform a detailed investigation of “surface channeling”. The experiments exhibit focusing in semichannels and critical conditions for axial and planar channeling. The dependence of the light emission of excited singly charged He + and neutral He 0 on incidence direction towards the (101) surface is different at small angles. An interpretation of this behaviour is proposed which is based on a correlation between energy loss and charge state of axially surface channeled projectiles.