Abstract
Dipolar interactions between silver particles arranged on a square two-dimensional grating give rise to characteristic features in the wavelength dependence of surface-enhanced Raman scattering from adsorbed molecules. The interactions produce two pronounced effects: first, they shift and broaden the plasmon resonance corresponding to the isolated particle, and second, they induce an additional sharp resonance feature at lower energy. The two enhancement maxima are separated by a minimum (cusp), which corresponds to the wavelength at which a grating order changes from radiating to evanescent in character. Dispersion relations describing the grating-induced resonances are presented. The consequences of the simultaneous enhancement of both the input and output electric fields are discussed, and the effects of imperfections in the particle shape are considered. The wavelength dependence of Raman scattering from p-nitrobenzoic acid adsorbed on a 380-nm-period two-dimensional array of silver spheroids was measured by means of an internal standard. Close agreement between experimental results and theoretical predictions was obtained.
© 1986 Optical Society of America
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