Optical resonances in bimetallic clusters and their relation to the electronic structure

The optical response of bimetallic clusters of composition ${\mathit{YA}}_{\mathit{x}}$, where A is an alkali metal and Y is a monovalent or divalent impurity, is studied by using the random-phase approximation upon a two-step jellium ionic background. With respect to the homologous pure clusters, the optical properties of mixed clusters are found to exhibit conspicuous variations that are directly related to corresponding drastic modifications in the electronic structure induced by the impurity atom. Parallel ab initio calculations are performed to test the adequacy of the two-step jellium model.