Dipole and quadrupole plasmon resonances in large sodium clusters observed in scattered light

Abstract

We study the dependence of the optical properties of clusters as a function of cluster size. The Mie theory is used to describe intensities of light scattered by growing clusters in directions orthogonal to the direction of the incident light beam. We assigned the maxima in scattered intensities to secondary fields due to plasmons excited in clusters with appropriate radius. The maxima in measured intensities of scattered light in “perpendicular” and “parallel” polarization geometry are attributed to excitation of dipole plasmon when cluster radius approaches 55 nm and of quadrupole plasmon when cluster size approaches 118 nm, respectively.