Electrodynamical forbiddance of strong quadrupole light-molecule interaction in the methane molecule and its manifestation in surface enhanced hyper Raman scattering spectra

Abstract

It is demonstrated in the framework of the dipole-quadrupole theory that strong quadrupole light-molecule interaction, which is responsible for the most enhancement in SEHRS experiences a so- called electrodynamical forbiddance in the methane molecule, which belongs to the T d symmetry group, due to the electrodynamical law divE = 0 and does not infuence on the formation of the SEHRS spectra. This forbiddance results in the fact that the lines caused by totally symmetric vibrations transforming after the unit irreducible representation, which are observed in symmetrical molecules with another groups of sufficiently high symmetry, such as pyrazine and phenazine, must be small or absent at all. In this case, in methane, the most enhanced lines are those caused by the vibrations transforming after the irreducible representation F 2.