Quantum-mechanical approach to surface-enhanced Raman scattering

Abstract

We present a microscopic model for surface-enhanced Raman scattering (SERS) from molecules adsorbed on small noble-metal nanoparticles. We demonstrate that, in nanometer-sized particles, SERS is determined by a competition between two distinct quantum-size effects: Landau damping of surface plasmon resonance and reduced screening near nanoparticle surface. The first mechanism comes from the discreteness of energy spectrum in a nanoparticle and leads to a general decrease in SERS. The second mechanism originates from the different effect of confining potential on <i>sp</i>-band and <i>d</i>-band electron states and leads to a relative increase in SERS. We calculate numerically the spatial distribution of local field near the surface and the enhancement factor for different nanoparticles sizes.