On Surface Plasmon Damping in Metallic Nanoparticles

Two possible mechanisms of surface plasmon (SP) oscillations damping in metallic nanoparticles (MNPs), not connected with electron-phonon interaction are investigated theoretically: a) the radiation damping of SP, b) resonant coupling of SP oscillations with electronic transitions in matrix. It is shown that the radiation damping rate is proportional to the number of electrons in MNP and therefore this channel of energy outflow from MNP becomes essential for relatively large particles. The investigation of second mechanism shows that the rate of SP oscillations energy leakage from MNP dos not depend on particle size and is fully determined by the optical characteristics of the matrix. It is demonstrated that for very small MNPs of 3-5 nm size, where the strong 3D size quantization effect suppresses the electron-phonon interaction, the resonance coupling in certain cases provides an effective energy outflow.