Abstract
The present paper is devoted to the description of optical absorptions in supported metallic particles smaller than the wavelength of light. The breaking of symmetry brought by the presence of the substrate and by the finite contact angle for the particle leads to a nonhomogeneous local field and allows excitation of multipolar absorption modes. Their energetic positions, oscillator strengths, and widths are calculated in the limit of zero damping by use of a multipolar expansion of the potential inside and around the island. The charge vibration pattern and the location of the field enhancements are clearly identified for each mode. Even if the dipolar mode is the most intense, the highlighting of the secondary modes in optical measurements is possible in peculiar experimental conditions. Some experiments of surface differential reflectivity spectroscopy for silver deposits on oxide substrates are given as examples.
- Received 26 February 2002
DOI:https://doi.org/10.1103/PhysRevB.65.235424
©2002 American Physical Society
