Photoluminescence from Metal Nanostructures: Dependence on Size

For decades, there have been multiple seemingly contradicting experimental reports on the dependence of the photoluminescence (PL) from metal nanostructures on their size. We reconcile these reports using a simple analytical formula that is found to match PL measurements well for a range of structures and illumination conditions. Our expression requires only knowledge of the local electric field and temperature and points to the physical quantities that determine the emission strength and its dependence on the size.