Plasmonic properties of metallic nanoparticles: the effects of size quantization

We examine the size quantization of plasmons in metallic nanoparticles using time-dependent density functional theory. For small particles in the quantum limit, we identify "quantum core plasmons" and "classical surface plasmons", both of which are collective oscillations comprised of multiple single-particle transitions. As particle size increases, the response of the classical surface plasmons becomes much larger than that of the quantum core plasmons.