FTIR spectrum of vinyl fluoride near 3.6 μm: rovibrational analysis of the ν₄+ν₇ band and modelling Coriolis resonances in a seven-level polyad

ABSTRACT

The Fourier transform infrared (FTIR) spectrum of vinyl fluoride, H₂C=CHF, has been widely investigated in the region of the ν₄+ν₇ combination band around 2800 cm⁻¹ at a resolution of 0.005 cm⁻¹. This vibration of A' symmetry gives rise to an a/b-hybrid band with a predominant a-type component. The rovibrational structure is strongly perturbed and the analysis has been rather complicated since this combination band is involved at least in a seven-level interacting polyad, including the ν₈+2ν₁₀, 2ν₈+ν₁₀, 2ν₇+ν₉, ν₇+ν₈+ν₁₂, ν₅+ν₉+ν₁₀ and ν₇+ν₁₀+ν₁₂ vibrational states. The study has been further complicated by the absence of transitions coming from the perturbers that were considered as dark states. The spectral analysis resulted in the identification of 936 transitions with J" ≤ 46 and K_a" ≤ 11, all belonging to the a-type component. Most of the assigned data have been fitted using the Watson's A-reduction Hamiltonian in the I^r representation and proper Coriolis perturbation operators. The model employed includes seven different resonances within a complex polyad resonant system and a set of spectroscopic constants for the ν₄+ν₇ combination band, for the dark states, and Coriolis coupling coefficients have been determined.

GRAPHICAL ABSTRACT

KEYWORDS:

• Vinyl fluoride
• infrared spectrum
• spectroscopic parameters
• Coriolis interactions
• ro-vibrational analysis

Acknowledgments

The authors wish to thank Professor M. Winnewisser for the opportunity to obtain high-resolution infrared spectra on the Giessen instrument some years ago.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

University Ca’ Foscari Venezia (ADiR funds) and Scuola Normale Superiore (GR16_B_TASINATO funds).