SURFACE-ENHANCED RAMAN-SCATTERING OF ADSORBATES

This review concentrates on the electronic contribution to surface-enhanced Raman scattering (SERS). This so-called 'chemical effect' is quantitatively separated from classical electromagnetic enhancement. It proceeds by increased electron-photon coupling at an atomically rough surface and by temporary charge transfer to adsorbate orbitals. These concepts are supported by various experimental results. The model accounts for the chemical specificity and vibrational selectivity of SERS and (partly) for the 'SERS specificity' of various metals.