CONTINUOUS SECONDARY LIGHT-EMISSION FROM SILVER FILMS - ON THE ORIGINOF THE INELASTIC BACKGROUND IN SERS

When cryocondensed silver films at 40 K are excited by laser photons i n the optical energy range, a broad distribution of secondary photons with an energy shift from 250 cm-1 to beyond 3500 cm-1 is emitted. Upo n annealing to 250 K we observe a narrowing of the emission band accom panied by an order of magnitude increase of the peak emission intensit y. The emission is quenched by oxygen exposure. The data are explained by a second order light scattering process involving surface state in traband excitations. Tentatively, the excitation band is assigned to t he intrinsic surface state at (111) facets.