Optical method for determining the shape anisotropy of sodium nanoparticles in an island film

The optical anisotropy of nanoparticle ensembles on transparent dielectric substrates is studied by fluctuation-polarization microscopy. The method is based on measuring fluctuations in the optical characteristics of small areas of a film. The hypothesis that the resonance absorption peaks correspond to the plasma oscillation modes in different directions of sodium particles, which are simulated by three-axial ellipsoids, is confirmed by the frequency dispersion of the polarization signal.