Photon mapping of individual Ag particles on MgO/Mo(001)

The optical properties of single Ag particles on an MgO thin film have been investigated with fluorescence spectroscopy performed in a scanning-tunneling-microscope setup. Depending on the point of excitation within the particle (top or side facet), two emission maxima are detected that are compatible with the in-plane and out-of-plane plasmons of the Ag deposits. The different excitation cross sections and spectral properties of the two modes give rise to characteristic intensity patterns in photon maps taken from individual particles.