Improved line list of 12CH4 in the 8850-9180 cm−1 region

Abstract Three spectra of normal samples of CH4 in the 8850-9180 cm−1 region were recorded at temperatures 296K, 254K, 208K by using a Fourier transform spectrometer in Tomsk with the cell path of 2.2 meters. Additional spectra of 12CH4 covering the same spectral range were obtained at 108 K with the cell path of 0.2 meters. The lower energy levels were corrected for 1029 lines available in the HITRAN [1] database in this range. Additionally, 275 new quantum assignments were added using ab initio variational calculations combined with the spectra analyses based on effective Hamiltonian and effective dipole transition moment fits. Simulations of observed spectra show that new line list is much more accurate for lower temperatures than the previous compilation included in HITRAN-2016. Finally, the lower state energies are provided for 1304 transitions that represents ∼66% of the integrated line intensity observed in this region at 296K. The sum of observed intensities between 8850 and 9180 cm−1 agree within 7% to the predicted value of ab initio variational calculations reported in the TheoReTS database ( http://theorets.univ-reims.fr ; http://theorets.tsu.ru ).