  High resolution low frequency Raman scattering measurements from embedded
AgAu nanoparticles unveil efficient scattering by harmonics of both the
quadrupolar and the spherical modes. Comparing the experimental data with
theoretical calculations that account for both the embedding medium and the
resonant Raman process enables a very complete description of the observed
multiple components in terms of harmonics of both the quadrupolar and spherical
modes, with a dominating Raman response from the former ones. It is found that
only selected harmonics of the quadrupolar mode contribute significantly to the
Raman spectra in agreement with earlier theoretical predictions.
