Trajectory dependent energy loss in grazing collisions of keV He atoms from a LiF(0Â 0Â 1) surface

Angular distributions for scattering of 12 keV He atoms from a LiF(0 0 1) surface under a grazing angle of incidence were recorded in coincidence with the projectile energy loss and the number of electrons emitted from the target surface during the collision. For scattering along the low indexed 〈1 1 0〉 and 〈1 0 0〉 directions of the crystal surface collisional rainbow peaks were observed. For scattering along a 〈1 1 0〉 direction the resulting rainbow peaks can be attributed to scattering from strings of anions which form active sites for charge exchange and emission of electrons. The data can be interpreted by trajectory computer simulations where charge transfer takes place from F− sites.