The Influence of First-Order Rotational Resonance Interaction on Certain Bands in the Infrared Spectrum of the Allene Molecule

Abstract

The Coriolis coupling between two degenerate vibrations in allene has been discussed. This theoretical treatment gives a satisfactory explanation of the main features of two perpendicular bands, which have been observed in the infrared absorptionspectrum of this molecule between 8 and 14μ. An analysis of the nuclear spin statistics has been carried out in order to account for the intensity alternations and to help in identifying the Q branches. A derivation of the frequency formula has been given on the basis of ordinary first‐order perturbation theory. Some emphasis is laid on the ambiguity in notation and the relation of this formula to others, reported in the literature. After making some reasonable assumptions with regard to the geometry of the molecule, we have obtained numerical values for the band centers and the various Coriolis coupling coefficients. A tentative suggestion has been made in partial explanation for the appearance of satellites between the main Q branches in the spectrum.