Rovibrational spectra of DCF3 in the 1000 cm−1 region: The ν5= 1 and ν6= 2 levels revisited

The degenerate fundamental vibrational level v5 = 1 (975.51 cm−1, E symmetry) and the overtone vibrational level v6 = 2 (1004.06/1005.98 cm−1, A1 + E symmetry) were reinvestigated with inclusion of their inter-vibrational couplings: the anharmonic Fermi interaction ( Δ K = 0 , Σ t Δ l t = Δ l 5 + Δ l 6 = ± 3 ), the second-order Coriolis resonance ( Δ K = ± 1 , Σ t Δ l t = ± 1 ), and the second-order α-resonance ( Δ K = ∓ 2 , Σ t Δ l t = ± 1 ). This required significant extension of assignments to high J and K rotational states where resonant crossings due to the latter two interactions occur. The newly assigned data from Fourier-transform IR spectroscopy were combined with rotational and laser-sideband rovibrational data pertaining to the v5 = 1 vibrational level, which were used already in a previous analysis, in a fully quantitative simultaneous fit.