EFFECT OF MULTIPLE SCATTERING IN THE INTERACTION OF LOW-ENERGY IONS WITH THE MAGNETITE SURFACE COVERED BY A THIN FILM OF CONDENSED XENON UNDER THE VERWEY TRANSITION,

W. Soszka and N.-T.H. Kim-Ngan, Institute of Physics, Pedagogical University, Podchorazych 2, 30-084 Krakow, Poland.

The energy specta of Ne⁺ and Ar⁺ ions scattered from the surface of the single crystal magnetite covered by a thin film of condensed xenon as a function of film-density were investigated. Under the small-angel geometry, the spectra contain two broad peaks of multiple ion/xenon scattering. While a large increase of the intensity of the high-energypeak (the first peak) with increasing the xenon thin-film thickness was observed, the low-energy peak (the second peak) is almost independent on the xenon pressure in the environment of the target for both bombarding ions. Relatively large energy losses were found for ions scattered from the ‘clean’ target (i.e. without xenon cover) and for ions formed the second peak in the energy spectra in case of the xenon-covered target. The experimental results can be well explained in the frame of the zig-zag model including the last re-ionized collision. The large effect of the phase transition (the Verwey transition of the magnetite) on ion scattering for the ‘clean’ target was a result of a change in the number of trajectories containing re-ionized collisions which strongly depends on the surface condition. Some suppression of the phase-transition effect was observed for the target covered by the xenon thin film. However, the presence of the second peak suggests than an arrangement of the first xenon layer on the target-surface exists and that the trajectory-effect still depends on the phase transition. In case of Ne⁺ bombardment due to a large ion penetration these effects are diffused.