28 September 2007 High energy plasmon resonances of silver nanoparticles
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Abstract
The behaviors of multiple resonances (or surface plasmon modes) produced by electrically small (the dimension of the sphere is much smaller than the wavelength) metallic nanospheres and coated nanospheres (whose outer radius is much smaller than the wavelength) are addressed in this paper. The plasmon resonances for electrically small nanospheres happen when the real part of the relative plasmon permittivity is near Re[εrn)] = -(n+1)/n, where n = 1, 2, ... The peak values of the scattered field are shown versus the angle of incidence for different n and electrical parameter q (q = k0a where k0 denotes the wavenumber in free space and a stands for the radius of the sphere). New formulas for extinction and scattering cross sections for both cases have been derived and given. For coated structures, the situation is a bit more complicated. The scattered field near resonances can be enhanced significantly with small dissipation of the relative permittivity. Within the instrumental error, the spectral range, within which the material Ag has low dissipation so that we can get the greatest scattering energy, is considered for the coated sphere. Two cases, i.e., silver core and coating, are investigated. The relative parameters such as the refractive indices of the core m1 and the coating m2, and the volume ratio f (f = a3/b3 where a and b denote the inner and outer radii of the coated sphere) have been derived at resonances. The near field energy intensity distributions around the coated sphere are also shown. The peak value of the scattered energy intensity is given for the lossless cases. This optical property may have potential applications in surface cleaning, etching, nanopatterning and so on.
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Le-Wei Li, Le-Wei Li, Hao-Yuan She, Hao-Yuan She, "High energy plasmon resonances of silver nanoparticles", Proc. SPIE 6642, Plasmonics: Nanoimaging, Nanofabrication, and Their Applications III, 664210 (28 September 2007); doi: 10.1117/12.737240; https://doi.org/10.1117/12.737240
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