A new approach to the surface plasma resonance of small metal particles

A differential equation for the polarizability of a small, continuum, spherically symmetric medium is developed in the local‐dielectric‐response approximation. The dynamic polarizability of a small metal sphere is then calculated through this equation using the Drude dielectric expression with the spatial dispersion of the free electron density given by the results of self‐consistent density functional calculations on jellium. This approach is used to examine the size dependence of the plasmon resonance absorption of small metal particles. It is able to account for the observed broadening and peak frequency shifts, both ‘‘red’’ and ‘‘blue,’’ as well as the additional absorption feature seen for small particles. To the extent that comparison with experimental data is possible, good agreement is found.