Analysis of the SEHR Spectra of Symmetrical Molecules on the Base of the Dipole-Quadrupole Theory

TL;DR

This paper investigates the SEHR spectra of symmetrical molecules using dipole-quadrupole theory, demonstrating forbidden bands and confirming the theory's ability to explain surface-enhanced optical phenomena.

Contribution

It provides a theoretical analysis of SEHR spectra based on dipole-quadrupole interactions, explaining forbidden bands and confirming the theory's applicability to various molecules.

Findings

Forbidden bands are demonstrated in certain molecules, confirming the dipole-quadrupole SEHRS theory.

The theory explains spectral features of pyridine and crystal violet.

Strong quadrupole light-molecule interaction is identified as the cause of surface-enhanced optical processes.

Abstract

The paper analyses the SEHR spectra of symmetrical molecules on the base of the dipole-quadrupole SEHRS theory. Existence of the bands, caused by vibrations transforming after the unit irreducible representations of corresponding symmetry groups is demonstrated. As it follows from the theoretical group analysis, these bands are forbidden in phenazine, pyrazine and in usual HRS in molecules belonging to a large number of groups (Cnh, D and higher symmetry groups for example). Their appearance strongly confirms the dipole-quadrupole SEHRS theory, which is able to explain other features of the SEHR spectra of these molecules also. Investigation of the SEHR spectra of pyridine and crystal violet demonstrates that they can be explained by this theory too. All these results point out the existence of the strong quadrupole light-molecule interaction, which is the reason of surface-enhanced optical processes.