Relationship between the giant enhancement of the Raman scattering and luminescence on nanostructured metallic surfaces

The relationship between the factors of giant enhancement of luminescence and inelastic (Raman) scattering of light at planar silver nanostructures is investigated. For this purpose, the variation of the enhanced luminescence and Raman signals with the distance between the nanostructure surface and a layer of test molecules is examined. It is found that, for lines whose spectral position is close to the wavelength of the excitation laser, the enhancement factor for the Raman scattering is proportional to the square of that for the luminescence signal. As the spectral shift between the Raman lines and the laser position increases, the above dependence becomes subquadratic. It is established that the spatial scale on which the enhancement is manifested is the same for both effects and amounts to $25$–$30$ nm.