High-resolution fourier transform and diode-laser spectroscopy of the v₆ fundamental of c₂f₆ and associated hot bands

High-resolution infrared spectra of the v₆ (713 cm⁻¹) band region of C₂F₆ vapor have been recorded at several temperatures. Spectra at 77, 200, and 300 K were recorded using a Fourier transform spectrometer with unapodized resolutions of 0.0018 cm⁻¹ (200 and 300 K) and 0.008 cm⁻¹ (77 K). Spectra with rotational temperatures in the range 5-50 K were recorded in a supersonic jet using diode-laser absorption spectroscopy. The v₆ band contains two clear sequences of hot-bands: one arises from the v₄ torsional vibration at 67.5 cm⁻¹; the other, shorter, weaker progression is built on the doubly degenerate v₉ vibration at 220 cm⁻¹. They lie to high and low wavenumbers of the fundamental band, respectively. Eleven series were assigned and fitted to these hot bands. A perturbed series in the v₄ sequence is considered, by analogy with the infrared spectrum of C₂H₆ vapor, to be caused by an xy-Coriolis interaction either between 5v₄ and v₉ + 2v₄ in the ground state or, in the upper state, v₆ + 5v₄ with v₆ + v₉ + 2v₄ or v₆ + 5v₄ with 2v₈. One further series resolved only in the jet spectrum and lying very close to the fundamental is almost certainly due to the v₆ fundamental of the isotopomer ¹³C¹²CF₆.