Laser infrared spectroscopy of vinyl fluoride in the 1280–1400 cm⁻¹ region

Abstract

The infrared spectra of CH₂=CHF have been investigated in the ν₅ and ν₆ band regions between 1280 and 1400 cm⁻¹, at a resolution of about 0.002 cm⁻¹, using a tunable diode laser spectrometer. These vibrations of symmetry species A′ give rise to a/b-hybrid bands with different contributions from both the components. Spectral analysis resulted in the identification of 1565 (J≤46, K _a ≤11) and 1651 (J≤48, K _a ≤15) transitions of the ν₅ and ν₆ fundamentals, respectively. Both bands are perturbed by the nearby states ν₈ + ν₉ and ν₉ + ν₁₁ through different Coriolis resonances and an anharmonic interaction. Using Watson's A-reduction Hamiltonian in the I^r representation and perturbation operators almost all the transitions have been fitted simultaneously to a model including six resonances within the tetrad ν₅/ν₆/ν₈ + ν₉/ν₉ + ν₁₁. A set of spectroscopic constants for the ν₅ and ν₆ bands, as well as parameters for the dark states ν₈ + ν₉ and ν₉ + ν₁₁ and coupling constants, have been determined. From spectral simulations the dipole moment ratio |Δμ _a /Δμ _b | was estimated to be 0.6 ± 0.1 and 2.0±0.3 for the ν₅ and ν₆ bands, respectively.

Acknowledgement

Financial support by MIUR, Rome, is gratefully acknowledged.