Study of the 5 um rotation-vibration spectrum of ¹²CD₃F

The spectrum of the ¹²CD₃F molecule in the 5 μm region which includes 24 states has been studied in detail. The observed bands 2υ₃⁽⁰⁾, υ₁, 2υ₅⁽⁰⁾ have been completely assigned including the doubled transitions in the regions where energy levels cross due to the effects of the many accidental resonances that couple the states which energetically lie very close to each other. These doubled transitions are critical to the analysis and understanding of any perturbed spectrum and ¹²CD₃F case is no exception. Two weak bands overlapping 2υ₃ and the P-side of υ₁ have been observed for the first time in a high pressure data run. They were assigned as (v₅ + V₆) and (v₂ + V₆) bands, respectively.

The data were taken, in a machine-readable form, using the completely computer controlled 5-meter Littrow instrument with apparent resolution between 0.010 and 0.028 cm^-1. The averaged spectrum used in the present analysis was deconvolved to its Doppler limit ∼0.005 cm^-1 at room temperature).

Single band analysis, including subband fits, resulted in the unperturbed values for 2υ₃⁽⁰⁾, υ₁, 2υ₅⁽⁰⁾, υ₄, and 2υ₂⁽⁰⁾ being reported. Most resonances that influence the positions of energy levels have been identified and reasonable estimates of their coupling constants obtained. Some of those resonances identified include Fermi resonances between and υ₁, 2υ₅⁽⁰⁾, and 2υ₂⁽⁰⁾, (ΔK = +1, Δℓ = +1) Coriolis resonance that couples state and υ₄⁺¹state and 2&upsilon₂⁽⁰⁾, ΔK = +2, Δℓ = -1 connecting υ₁ and (&upsilon₃ + υ₅)^-1.

Finally, preliminary results of a 12-state global analysis that treats all resonances, except (ΔK = ±2, Δℓ = -1)-type, simultaneously are reported. Lists of the measured frequencies for all transitions in the observed bands with the corresponding calculated ones are presented. The calculated frequencies are based on a simple unperturbed model to show the severity of the perturbations as can be seen from the residuals included in the tables.