The backscattered energy spectrum of a beam of MeV ions incident along a major axial direction of a single crystal displays a high energy peak which represents the interaction of the beam with the surface region of the solid. Measurements under U.H.V. conditions, on well characterized surfaces, yield information on the thermal vibration amplitude, relaxation and reconstruction of the first monolayer(s) of the solid; this information is not easily obtainable by standard surface physics techniques. Such studies are of importance in the field of catalysis and semiconductors as well as the fundamental understanding of surfaces. An U.H.V. system for surface analysis studies couple to a 3.75 MeV Van de Graaff accelerator shall be described. Measurements of the surface peak intensity for W(100) are presented and shown to be in good agreement with theoretical models of the scattering process. The interpretation of such measurements in terms of surface physics parameters will be discussed.
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