Reaction of chlorine with Ag surfaces has been studied at 300 K with X-ray photoelectron spectroscopy and Auger depth profiling over a wide range of Cl2 exposures. Formation of AgCl and subsurface diffusion are observed. At exposures lower than 107 L, the Ag-Cl2 reaction is logarithmic in time and the surface layer is Ag enriched. This behavior can be related to a field-assisted diffusion mechanism known from oxidation of metal surfaces. At higher exposures, however, a t1/2 time dependence of the chlorination reaction is found. The Cl penetration saturates, and a stoichiometric AgCl layer is formed on the surface. It is further observed that a solid AgCl can be reduced to metallic Ag in the surface region when bombarded by Ar+ ions. Irradiation by X-ray photons can cause more complex chemical changes on the solid surfaces. © 1987 Elsevier Science Publishers B.V.