Plasmon-phonon coupling and resonant raman scattering of silver clusters
Absorption and low-frequency Raman scattering experiments have been performed on thin films consisting of small silver clusters embedded in a porous, alumina matrix. When the Raman excitation wavelength is close to the maximum (≈ 420 mm) of the Mie hand (dipolar surface plasmon resonance) the Raman spectra exhibit a strong band located around 10 cm−1, the maximum of which depends on the mean cluster diameter Open image in new window in the sample according to the approximate law Open image in new window . The Raman band corresponds to the excitation of the quadrupolar vibration mode of the clusters. Moreover, the maximum of the Raman hand shifts towards lower frequencies when the excitation light is shifted to the red. This feature, as well as the rather large Nile-band width, is thought to reflect the ellipsoidal shape distribution of part of the embedded clusters.
PACS36.40.-c Atomic and molecular clusters 36.20.Ng Vibrational and rotational structure, infrared and Raman spectra 63.20.Pw Localized modes
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