Effect of displacement and distortion of potential energy surfaces and overlapping resonances of electronic transitions on surface-enhanced Raman scattering: models and ab initio theoretical calculation

A previously developed theory for the temperature-dependent resonance Raman scattering is used to study the surface-enhanced Raman scattering. Two models, the displaced oscillator model and the displaced-distorted oscillator model, based on the harmonic potential energy surfaces are carried out to calculate the surface-enhanced Raman scattering excitation profiles of the pyridine molecule adsorbed on a silver electrode, for which the density functional theory method is applied to evaluate the potential energy surfaces of the adsorption structure. In this framework, the distortion effect on the surface-enhanced Raman scattering will be discussed by comparing both models. The overlapping resonance of multiexcited electronic transitions is also studied, in which the interference between electronic transitions has been taken into account. It will be used to study the abnormal band at 1005.6 cm(-1) with the exciting radiation 457.9 nm.