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4 pags., 1 fig. ; The rich structure of surface plasmon modes localized in noble metal nanoparticles is explored by optical spectroscopy, spatially resolved electron energy-loss spectroscopy, and by electron beam-induced radiation emission. Spectral features and spatiallyresolved maps of surface plasmon modes are calculated by using the boundary element method. Our results show the unmatched capability of electron beams for spectrally and spatially probing plasmon modes in metal nanoparticles. ; We acknowledge support from the European Union (NMP4-SL-2008-213669-ENSEMBLE, ICT-2009-4-248909-LIMA, and FP7-ICT-2009-4-248855-N4E) and the Spanish MICINN (MAT2010-14885 and Consolider NanoLight.es). V.M. acknowledges the Spanish CSIC -JAE grant. ; Peer reviewed

We report on spectral imaging within individual silver split-ring resonators (SRRs) operating in the near infrared-visible range. We classified the optical eigenmodes from the measurement of their energies and nanometer scale spatial distributions. They are plasmonic standing waves that show great similarities with that of nanoantennas. We, however, evidenced marked differences in the near-field electric field lines' spatial distribution and the energies' dispersion. We also showed that the subwavelength defect's influence on the SRRs' eigenmodes spatial distribution is small. © 2010 The American Physical Society. ; The authors acknowledge financial support from the European Union under the Framework 6 program under a contract for an Integrated Infrastructure Initiative. Reference 026019 ESTEEM. ; Peer Reviewed

9 pags, 6 figs ; Imaging localized plasmon modes in noble-metal nanoparticles is of fundamental importance for applications such as ultrasensitive molecular detection. Here, we demonstrate the combined use of optical dark-field microscopy (DFM), cathodoluminescence (CL), and electron energy-loss spectroscopy (EELS) to study localized surface plasmons on individual gold nanodecahedra. By exciting surface plasmons with either external light or an electron beam, we experimentally resolve a prominent dipole-active plasmon band in the far-field radiation acquired via DFM and CL, whereas EELS reveals an additional plasmon mode associated with a weak dipole moment. We present measured spectra and intensity maps of plasmon modes in individual nanodecahedra in excellent agreement with boundary-element method simulations, including the effect of the substrate. A simple tight-binding model is formulated to successfully explain the rich plasmon structure in these particles encompasing bright and dark modes, which we predict to be fully observable in less lossy silver decahedra. Our work provides useful insight into the complex nature of plasmon resonances in nanoparticles with pentagonal symmetry. © 2012 American Chemical Society. ; We acknowledge support from the European Union (NMP4-2006-016881-SPANS, NMP4-SL-2008-213669-ENSEMBLE, FP7-ICT-2009-4-248909-LIMA, and FP7-ICT-2009-4-248855-N4E), the Spanish MICINN (MAT2010-14885, MAT2010-15374, and Consolider NanoLight.es), and Ibercivis. V.M. acknowledges the Spanish CSIC - JAE grant. G.A. and N.I.Z. acknowledge support of the EPSRC and the Royal Society (London). L.M.L.-M. acknowledges funding from the ERC (Advanced Grant PLASMAQUO, 267867).