Abstract
The surface-enhanced Raman scattering (SERS) spectra of 4-methylpyridine (4-MP) have been recorded at different electrode potential versus saturated Ag/AgCl/KCl reference electrode. By comparing the relative intensity of the SERS with the Raman spectrum of the aqueous solution it is possible to determine that 12, 6a, δ(CH) and especially 8a modes are strongly enhanced. In this work, it is demonstrated that these vibrations are closely related to Franck–Condon factors of a resonant photoinduced charge transfer (CT) mechanism similar to a resonance Raman (RR) process. The theoretically calculated ΔQ displacements represent the differences between geometries of the potential energy minima of the states involved in the resonant process, allowing to calculate the relative intensities in RR from the Peticolas’ equation. These calculated intensities are in a perfect agreement with the experimental behavior.
Published Version
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