EELS and optical response of a noble metal nanoparticle in the frame of a discrete dipole approximation

Surface plasmons of noble metal nanoparticles have recently been studied by Electron Energy-Loss Spectroscopy (EELS) performed in an electron microscope. We present here the basic formalism for EELS simulations in a Discrete Dipole Approximation (DDA) framework for such surface excitations. We compare EELS data and optical properties of a silver triangular nanoprism and show that the spatial variation of surface plasmon excitation probabilities allows to discriminate modes of similar energies. We also emphasize the importance of the substrate polarization effect to reliably describe experimental data.