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An in situ scanning tunneling microscope (STM) was used to observe the morphological changes accompanying the selective dissolution of Ag h m low-Ag content Ag-Au alloys in dilute perchloric acid This study was undertaken to explore the role of surface diffusion in alloy corrosion pmcesses. These d t s are interpreted within the h e w o r k of the kink-ledge-terrace model of a aystal surface and a recent model of alloy corrosion based on a variant of percolation theory. The corrosion process leads to roughenhg of the surface by dissolution of Ag atoms h m terrace sites. h e a l i n g or smootheniug of the surface occurs by vacancy migration through dusters and the subsequent annihilation of dusters at terrace ledges.

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strong O1 2' and a weak OH" ligand in the axial direction and that the strong O2" ligand is preferable to the 5 = 1 spin state of the central metal ion.

We report molecular beam scattering of hyperthermal Xe atoms over an energy range 1<Ei(eV)<10 from single crystal surfaces of GaAs(110), Ag(100), and Ge(100). The angular distributions from the corrugated surfaces show sharp backscattered rainbow maxima related to the topography of the crystal surface. In contrast the smooth surfaces yield quasispecular lobes suggestive of structure scattering. The large energy loss for all surfaces scales on average with the energy of local normal motion. A simple binary interaction model is developed which accounts for many of the phenomena observed from corrugated surfaces. With the aid of a comparison classical trajectory study, these results provide some understanding of the mechanism by and extent to which a solid can dissipate the energy of a hyperthermal collision.