Shadowing and focusing effects in the angular distributions of low-energy rare-gas ions scattered from solid surfaces

Low-energy rare-gas ion scattering spectroscopy (ISS) has been improved by the use of neutral beams as projectiles, which we call neutral beam incident ion scattering spectroscopy (NBISS). Features of the two techniques (NBISS and ISS) have been discussed on the basis of electron exchange between projectiles and solid surfaces. The shadowing and focusing effects are clearly observed in the NBISS results, while these effects are sometimes suppressed in the ISS results. It is found that the occurrence of the ionization of neutralized rare-gas atoms is necessary for the appearance of these effects. On the basis of such inspections, the guidelines for applying NBISS and ISS to surface structure analysis are given.