Fermi resonance in a molecule adsorbed on plasmonic metal film

In this work, the effect of electric field induced by localized plasmon excitation in nanostructured metal film on the vibrational spectrum of adsorbed organic molecule is studied theoretically. By using the Green function formalism, we show that electric field can significantly influence both the frequencies of the molecular vibrations and the anharmonicity constant. Consequently, if Fermi resonance can take place in the adsorbed molecule, it is spectral manifestation (in Raman spectra) will also be modified by the electric field of plasmon. We illustrate the effect with a CO2 molecule adsorbed on nanostructured gold surface, a situation relevant to the application of Surface-Enhanced Raman Scattering (SERS) or other plasmon-mediated phenomena. The obtained in these work analytical expressions are shown to describe well spectral features in earlier experimental SERS studies on CO2.

Automated summary

This study examines the influence of electric field induced by localized plasmon excitation in nanostructured metal film on the vibrational spectrum of adsorbed organic molecule using the Green function formalism. It is shown that the electric field can significantly affect the frequencies of molecular vibrations and the anharmonicity constant. Additionally, if Fermi resonance occurs in the adsorbed molecule, its spectral manifestation in Raman spectra will also be altered by the plasmon's electric field.