High-resolution FTIR spectroscopy of HCFC-31 in the 950−1160 cm⁻¹ region: rovibrational analysis and resonances in the ν₄, ν₉ and ν₅+ν₆ bands of CH₂³⁵ClF

Abstract

The FTIR spectrum of CH₂ClF (natural isotopic mixture) was investigated in the ν₄, ν₉  and ν₅+ν₆  band region between 950 and 1160 cm⁻¹ at the resolution of 0.004 cm⁻¹. The ν₄ and  ν₅+ν₆  vibrations of A′ symmetry give rise to a/b hybrid bands with a predominant a-type component. The ν₉ vibration of A^″ symmetry, expected with a c-type band contour, shows an intense Coriolis-induced parallel component (ΔK_a = 0, ΔK_c = 0) derived from mixing with the v₄ = 1 vibrational state. The high-resolution spectra of ν₉ and   ν₅+ν₆  have been analyzed for the first time, while the assignments of the ν₄ band, previously investigated, have been extended to higher J and K_a values in the b-type component. The spectral analysis resulted in the identification of 1508, 809 and 349 transitions for the ν₄, ν₉ and ν₅+ν₆  bands of CH₂³⁵ClF, respectively. Besides the strong first-order a- and b-type Coriolis resonances between ν₄ and ν₉, the  ν₅+ν₆  vibration was found to interact through a c-type Coriolis with the ν₄ and 3ν₆. High-order anharmonic resonance (ΔK_a = ±2) between ν₄ and  ν₅+ν₆  was also established. All the assigned data were simultaneously fitted using the Watson's A-reduction Hamiltonian in the I^r representation and the relevant perturbation operators. The model employed includes five types of resonances within the tetrad ν₄/ν₉/ν₅+ν₆/3ν₆. Α  set of spectroscopic constants for ν₄, ν₉ and ν₅+ν₆ bands as well as parameters for the dark state 3ν₆ and seven coupling terms have been determined. The simulations performed in different spectral regions satisfactorily reproduce the experimental data.

Keywords:

• chlorofluoromethane
• infrared spectrum
• spectroscopic parameters
• Coriolis interaction
• rovibrational mixing

Acknowledgements

Nicola Tasinato thanks University Ca’ Foscari Venezia for his post-doctoral position.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work has been supported by Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR) through PRIN 2012 funds for the project STAR (Spectroscopic and Computational Techniques for Astrophysical and Atmospheric Research) [prot. no. 20129ZFHFE_003], by University Ca’ Foscari Venezia (ADiR funds) and by University of Bologna (RFO funds).