A simple classical model for estimating the electromagnetic enchancement in surface enhanced Raman scattering from molecules adsorbed on metal particles coated with overlayers.

I describe an easy to use model for estimating the electromagnetic enhancements of Raman scattering from molecules adsorbed on overlayers on metal islands. The model is valid quantitatively in the limit of low adsorbate coverage and small island sizes. It can be used by experimenters to obtain a qualitative estimate of the effect of overlayers and spacers on metal island film resonances and Raman scattering from adsorbates on the overlayers. The model is evaluated for Au, Ni, nonabsorbing dielectric, and Au and Ni cluster overlayers on silver islands.