Plasmon-dispersion corrections and constraints for surface selection rules of single molecule SERS spectra

The problem of extracting information from relative intensities of Raman peaks in surface-enhanced-Raman-scattering (SERS) is intimately related to several important topics in the technique. Among them: (i) the possibility (or sometimes impossibility) of observing surface selection rules in different situations, (ii) the role of analyte resonance conditions, (iii) the crucial inclusion of plasmon-resonance dispersion corrections in the analysis of relative Raman intensities among peaks, and (iv) the connection of these phenomena with (broader) issues like surface-enhanced fluorescence (SEF). This paper deals with the underlying connections among these (apparently disconnected at first sight) topics. The technique is now at a mature stage to review the aforementioned phenomena from a unified point of view; thus pinpointing the most important issues, clarifying concepts that have been historically confusing (or treated in isolation), and paving the road for future developments.