A note on a quantum theory of surface enhanced Raman scattering

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Abstract
A ‘coupled mode’ set of eigenfunctions is obtained for investigations of the quantum theory of surface enhanced Raman scattering by a physiadsorbed molecule on a metal surface. The enhancement ratio R(ω) for scattering cross‐section of adsorbed to free molecules is calculated. The theory is applied to the pyridine on silver system. In the classical limit, using a geometry with flat silver surface, the ‘image enhancement’ model is recovered, and a large enhancement can be forced if unrealistic values of parameters are used. In the correct quantum theory a sharply peaked enhancement of about 10−3 of that reported can be obtained at laser energy about 3.7 eV. The conventional image model is thus not supported by the quantum theory. Surface roughness needs to be incorporated into this coupled mode theory.