Electrodynamical forbiddance of a strong quadrupole light-molecule interaction in fullerene C60 and its withdrawal in fullerene C70

TL;DR

This paper investigates how symmetry reduction in fullerene C70 relieves electrodynamical forbiddance of quadrupole interactions seen in C60, leading to observable spectral lines in SERS spectra that confirm a dipole-quadrupole mechanism.

Contribution

It demonstrates the symmetry-based withdrawal of electrodynamical forbiddance in C70, revealing new spectral lines and supporting the dipole-quadrupole SERS mechanism.

Findings

C70 shows forbidden lines in SERS spectra due to symmetry reduction.

Electrodynamical forbiddance is absent in C70, unlike in C60.

Spectral evidence supports the dipole-quadrupole SERS mechanism.

Abstract

It is demonstrated that in fullerene C70 which can be considered as a deformed fullerene C60 in some sense there is a withdrawal of an electrodynamical forbiddance of a strong quadrupole light-molecule interaction which is realized in the fullerene C60. This situation occurs because of the reduction of symmetry of C60 from the icosahedral symmetry group Yh to the group D5h. The withdrawal results in appearance of the lines in the SERS spectra of C70 which are forbidden in usual Raman scattering and are allowed in infrared absorption while such lines are forbidden in the SERS spectrum of the fullerene C60 due to the electrodynamical forbiddance. The measured SERS spectra of C70 demonstrates existence of such lines that strongly confirms our ideas about the dipole quadrupole SERS mechanism.