Measurements and modeling of long-path 12CH4 spectra in the 4800–5300cm−1 region

• Published in: Journal of quantitative spectroscopy & radiative transfer Vol. 138; pp. 116 - 123
• Main Authors: Nikitin, A.V., Thomas, X., Régalia, L., Daumont, L., Rey, M., Tashkun, S.A., Tyuterev, Vl.G., Brown, L.R.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2014
• Subjects: Long path FTIR; Near infrared methane; Outer planets; Tetradecad; Titan; Transparency window; Near infrared methane; Transparency window; Tetradecad; Titan; Long path FTIR; Outer planets
• ISSN: 0022-4073; 1879-1352
• DOI: 10.1016/j.jqsrt.2014.02.005

A new study of 12CH4 line positions and intensities was performed for the lower portion of the Tetradecad region between 4800 and 5300cm−1 using long path (1603m) spectra of normal sample CH4 at three pressures recorded with the Fourier transform spectrometer in Reims, France. Line positions and intensities were retrieved by least square curve-fitting procedures and analyzed using the effective Hamiltonian and the effective Dipole moment expressed in terms of irreducible tensor operators adapted to spherical top molecules. An existing spectrum of enriched 13CH4 was used to discern the isotopic lines. A new measured linelist produced positions and intensities for 5851 features (a factor of two more than prior work). Assignments were made for 46% of these; 2725 experimental line positions and 1764 selected line intensities were fitted with RMS standard deviations of 0.004cm−1 and 7.3%, respectively. The RMS of prior intensity fits of the lower Tetradecad was previously a factor of two worse. The sum of observed intensities between 4800 and 5300cm−1 fell within 5% of the predicted value from variational calculations. •2725 experimental line positions were retrieved and modeled to 0.004cm−1.•1764 experimental line intensities were modeled to 7.3%.•A line list of assigned features was made with intensities at 296K.•The integrated intensities matched variational calculations to within 5%.