  Nanometer-sized metal particles exhibit broadening of the localized surface
plasmon resonance (LSPR) in comparison to its value predicted by the classical
Mie theory. Using our model for the LSPR dependence on non-local surface
screening and size quantization, we quantitatively relate the observed plasmon
width to the nanoparticle radius $R$ and the permittivity of the surrounding
medium $\epsilon_m$. For Ag nanospheres larger than 8 nm only the non-local
dynamical effects occurring at the surface are important and, up to a diameter
of 25 nm, dominate over the bulk scattering mechanism. Qualitatively, the LSPR
width is inversely proportional to the particle size and has a nonmonotonic
dependence on the permittivity of the host medium, exhibiting for Ag a maximum
at $\epsilon_m\approx2.5$. Our calculated LSPR width is compared with recent
experimental data.
