Electrodynamical forbiddance of the quadrupole mechanism of the infrared absorption enhancement in the methane molecule

Abstract

Peculiarities of the phenomenon of infrared absorption enhancement in the methane molecule are considered. It is demonstrated, that a part of the terms in the cross section, associated with quadrupole-radiation-molecule interaction and responsible for the enhancement of the band, caused by the breathing vibration vanish due to some electrodynamic forbiddance. This forbiddance is caused both by the molecule symmetry Td and by the electrodynamical properties of the quadrupole interaction. It must be present in all molecules, belonging to the "cubic" groups T, Th, Td, O, and Oh. The result is the absence of the band, caused by the breathing vibration, while in other symmetrical molecules, such band must be strongly enhanced. © 1994.