High-resolution Fourier transform infrared (FTIR) spectra of methyl fluoride (CH3F) were recorded in the mid- and far-infrared regions using the Bruker IFS 125HR spectrometers at GSMA (Reims, France) and at the SOLEIL synchrotron facility (Saint-Aubin, France). The measurements cover both the pure rotational transitions of the ground state (10–100 cm−1) and the vibrational triad region (1950–2450 cm−1), which includes the 2, , and 2 bands. Spectra were recorded under various pressure conditions to optimize line visibility, with a high resolution. Line assignments were performed using predictions from the tensorial effective Hamiltonian implemented in the MIRS package, together with a newly developed automated assignment tool, SpectraMatcher, which facilitates line matching and discrimination of CH3F transitions from overlapping CO2 features. More than 5000 transitions (up to in the ground state and up to in the triad and ) were assigned and included in a global fit. The sixth-order tensorial effective Hamiltonian model yielded excellent agreement with experiment, with root mean square (RMS) deviations better than 7 × 10−4 cm−1 across all regions. This paper presents the first continuous rovibrational study of CH3F over both the triad and far-infrared ground state regions. The improved accuracy from previous studies stems from the improved set of effective Hamiltonian parameters which will also form a good basis from future applications in atmospheric modelling and spectroscopic databases.
29 September 2025 in Journal of Quantitative Spectroscopy and Radiative Transfer