Manifestation of Strong Quadrupole Light-Molecule Interaction in the SER and SEHR Spectra of Pyrazine and Phenazine

TL;DR

This paper explains the appearance of forbidden lines in SEHR spectra of pyrazine and phenazine through a dipole-quadrupole theory, highlighting strong quadrupole light-molecule interactions near rough metal surfaces.

Contribution

It introduces a dipole-quadrupole theoretical framework to explain forbidden lines in SEHR spectra, emphasizing the role of strong quadrupole interactions in surface-enhanced phenomena.

Findings

Forbidden lines explained by quadrupole interactions

Strong quadrupole light-molecule interaction confirmed

Surface field variations are crucial for spectral features

Abstract

It is demonstrated that explanation of appearance of strong forbidden lines in the SEHR spectra of pyrazine and phenazine, caused by totally symmetric vibrations and also other details of their SER and SEHR spectra can be made on the base of the dipole-quadrupole theory. The main point of this theory is conception of a strong quadrupole light molecule interaction, arising in surface fields strongly varying in space near a rough metal surface. Existence of the pointed lines is a good corroboration of existence of the strong quadrupole light-molecule interaction.