Figure 1.
In blue: The normalized extinction cross-section Cext from Eq. 2. Extinction by gold spheres of 5 nm radius in aqueous suspension as a function of the wavelength of the incident light. In red: The normalized Raman enhancement, G(λ) Eq. 4 vs excitation wavelength for gold spheres of radius much smaller than the wavelength evaluated for a Raman shift of 0 nm.