Influence of interband electronic transitions on the optical absorption in metallic nanoparticles

Electronic interband transitions influence the surface plasmon resonance in metallic nanoparticles significantly. We derive expressions for the resonance frequency, the bandwidth and the maximum of the light absorption cross section of noble metal nanoparticles, taking into account the interband transitions in the dielectric function. We propose a simple method for determining the width of the plasmon resonance based on an analysis of the dielectric permittivity of the constituent metal.