Study of tarnished films formed on silver by exposure to H2S with the surface-plasmon resonance technique

The surface-plasmon resonance (SPR) technique is used to study the growth rate and the nature of Ag(2)S films formed on a silver (Ag) film exposed to an atmosphere containing 50% H(2)S for different times. The thickness of the Ag(2)S layer formed, estimated from shifts in the experimental SPR curves, showed a saturation tendency after an initial linear increase. Theoretical analysis of the curves when Ag and Ag(2)S are treated as two uniform layers and Ag-Ag(2)S as a composite layer showed that radiation damping is mainly responsible for the increase of half-width and dip reflectance, indicating that the Ag(2)S film formed is rough and discontinuous.