Improved line list of 12CH4 in the 4100–4300 cm−1 region. (March 2022)

• Record Type: Journal Article
• Authors: Rodina, A.A.; Nikitin, A.V.; Manceron, L.; Thomas, X.; Daumont, L.; Rey, M.; Sung, K.; Protasevich, A.E.; Tashkun, S.A.; Tyuterev, Vl. G.
• Is Part Of: Journal of quantitative spectroscopy & radiative transfer. Volume 279(2022)
• Publication Date: 2022-03
• Subjects: High resolution spectra -- CH4 -- Methane -- Octad -- Long path FTIR -- Vibration-rotation states -- Intensities -- Infrared absorption -- Effective Hamiltonian -- GeoCarb; Spectrum analysis -- Periodicals; Radiation -- Periodicals; Analyse spectrale -- Périodiques; Rayonnement -- Périodiques; Radiation; Spectrum analysis; Periodicals; 543.0858
• DOI: 10.1016/j.jqsrt.2021.108021
• Languages: English
• ISSNs: 0022-4073

Abstract

Highlights: 12, 378 line positions and intensities were retrieved in the 4100–4300 cm −1 region. More than 11, 520 new assignments were made in the region. 6963 experimental line positions were modeled to 0.0015 cm −1 . 6006 experimental line intensities at 296 K were modeled to 4.71% rms. Abstract: Four spectra of methane in natural isotopic abundance in the 4100–4300 cm −1 region were recorded by using a Fourier transform spectrometer in Reims, France at long paths (202 m, 602 m, 1604 m and 1804 m) and different pressures. Additional spectra of 12 CH4 covering the same region were obtained at 100–123 K for different pressures, 93 m path length at Synchrotron SOLEIL in Paris for different pressures and were used to measure low-J lines. Spectra of 12 CH4 and 13 CH4 obtained at 80 K at JPL in Pasadena were used for additional frequency calibrations. Line positions and intensities were retrieved by non-linear least-squares curve-fitting procedures and analyzed using effective Hamiltonian and effective dipole transition moment models. A new measured line list contains positions and intensities for 12, 378 features. Quantum assignments were made for more than 11, 520 new transitions, which represent ∼99% of the integrated line intensity observed in this region. Some of 4556 hot band transitions for (Dyad – Tetradecad) system were assigned. The resulting list of lines is significantly more accurate than previous empirical compilations. All assigned 6963 line positions were fitted to RMS standard deviations of 0.0015 cm −1 . The sum of the observed intensities between 4100 and 4300 cm −1 falls within 5% of the predicted value from ab initio variational calculations reported in the TheoReTS database (http://theorets.univ-reims.fr ; http://theorets.tsu.ru ).