Influence of lateral interactions on Raman scattering by molecules adsorbed on a solid surface: a model study

This article presents results of theoretical description and numerical modeling of processes like Raman scattering by molecular layers obtained with account of lateral interactions in such layers. Green functions for a half-space with an ultra-thin film is obtained from a self-consistent Dyson equation. Expression for the response of such a system on shifted frequency, which has straightforward physical interpretation, is given. It is shown that lateral interactions create new modes localized on the ultra-thin film and it is the interaction with these modes, which can enhance response of such a film in different processes. Numerical calculations based on the presented theoretical results exhibit the possibility to enhance Raman scattering by adsorbed molecules both for p- and s-polarized light. Detailed qualitative analysis of these processes clearly demonstrates that enhancement may be reached just by interaction with discussed modes. Obtained enhancement is not giant for Raman scattering, but it is remarkable and can be reached for any light polarization and for bigger variety of systems than surface enhanced Raman scattering can.