Manifestation of strong quadrupole light-molecule interaction in the SER and SEHR spectra of pyrazine and phenazine

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.

Graphical abstractDownload high-res image (94KB)Download full-size imageHighlights► Here we estimated and demonstrated strong enhancement of the SER and SEHR cross-sections. ► We bring selection rules for contributions, which form these cross-sections. ► On this base we interpreted successfully the SER and SEHR spectra of pyrazine and phenazine. ► The results explain appearance of forbidden lines in these spectra. ► Coincidence with experimental SER and SEHR spectra of pyrazine and phenazine is excellent.