Abstract
The ability of relevant current theories of secondary ion emission to explain experimental ion energy spectra obtained from polycrystalline Al, Sc, Ti, V, Cr, Fe, Ni, Cu, Hf, W and Au is analysed. It is shown that our present understanding or interpretation of the physics of the emission of secondary ions seems incapable of accounting for the observed changes in the energy spectra as a function of surface contamination or oxidation.