  Non-local effects in the optical response of noble metals are shown to
produce significant blueshift and near-field quenching of plasmons in
nanoparticle dimers, nanoshells, and thin metal waveguides. Compared with a
local description relying on the use of frequency-dependent dielectric
functions, we predict resonance shifts as large as 10% and field-intensity
reduction of an order of magnitude at inter-particle distances or metal
thicknesses below 2 \AA. Our results are based upon the specular-reflection
model combined with a suitable non-local extension of measured local dielectric
functions. We present a roadmap to design plasmon resonances in nanometer
metallic elements with application to optical antennas and improved
photovoltaic, light-emitting, and sensing devices.
