  Metal photoluminescence (MPL) originates from radiative recombination of
photoexcited core holes and conduction band electrons. In metal nanostructures,
MPL is enhanced due to the surface plasmon local field effect. We identify
another essential process in plasmon-assisted MPL - excitation of Auger
plasmons by core holes - that hinders MPL from small nanostructures. We develop
a microscopic theory of plasmon-enhanced MPL that incorporates both
plasmon-assisted enhancement and suppression mechanisms and derive the
enhancement factor for MPL quantum efficiency. Our numerical calculations of
MPL from Au nanoparticles are in excellent agreement with the experiment.

Mesoscale and Nanoscale Physics;Optics