The Infra-Red Absorption Spectrum of Hexafluoroethane Gas

Abstract

The infra‐red absorption of gaseous hexafluoroethane between 2 and 25μ has been investigated with prism spectrometers of high resolution. On the basis of normal vibration calculations and the known Raman frequencies it has been possible to interpret all but 3 of the 51 observed absorption maxima. Only combination bands permitted for both the staggered (D_3d) and the eclipsed (D_3h) model were used in the assignment of bands. Five fundamental frequencies have been determined in addition to the six obtained from the Raman spectrum. No combination band involving the remaining frequency, associated with the torsional oscillation of one CF₃ group relative to the other, could be identified. An attempt to determine the moments of inertia of the C₂F₆ molecule from the envelope of the strongest parallel band gave unsatisfactory results.