skip to main content


This content will become publicly available on December 6, 2018

Title: Multispectrum analysis of air-broadened spectra in the ν 3 Q branch of 12CH4

In this paper, we report experimental measurements of spectral line shape parameters (air-broadened width, shift, and line mixing coefficients) for several transitions in the ν 3 Q branch of methane in the 3000–3023 cm -1 region. 13 high-resolution, room temperature laboratory spectra of pure methane and air-broadened methane recorded with two different Fourier transform spectrometers are fitted. 12 of these spectra were acquired at 0.01 cm -1 resolution with the McMath-Pierce FTS at the National Solar Observatory on Kitt Peak, and one higher-resolution (~0.0011 cm-1) low pressure methane spectrum was obtained with the Bruker IFS-120HR FTS at the Pacific Northwest National Laboratory, in Richland, Washington. All the spectra were obtained using high purity natural samples of CH 4 and lean mixtures of the same natural CH 4 in dry air. For the 12 spectra recorded at Kitt Peak, three different absorption cells (L= 5, 25 and 150 cm) were used while the methane spectrum at PNNL was obtained using a 19.95 cm long absorption cell. For the analysis, an interactive multispectrum nonlinear least squares fitting software was employed where all the 13 spectra were fitted simultaneously. An accurate and self-consistent set of line parameters were determined by constraining a fewmore » of those for severely blended transitions. Line mixing was measured for fourteen transition pairs for the CH 4-air collision system. Lastly, a constant speed dependence parameter, consistent with measured speed dependence values obtained in other methane bands, was applied to all the transitions included in the fitted region. The present measurements are compared to values reported in the literature.« less
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. College of William and Mary, Williamsburg, VA (United States). Department of Physics
  2. University of Massachusetts Lowell, Lowell, MA (United States). Department of Environmental, Earth, and Atmospheric Sciences
  3. Sorbonne Universites, UPMC Univ. Paris (France). Laboratoire de Meteorologie Dynamique
  4. NASA Langley Research Center, Hampton, VA (United States). Science Directorate
  5. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Quantitative Spectroscopy and Radiative Transfer
Additional Journal Information:
Journal Volume: 206; Journal ID: ISSN 0022-4073
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
Country of Publication:
United States
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 58 GEOSCIENCES; Methane; 12CH4; ν3 Q branch; Relaxation matrix element coefficients; Lorentz air broadening; Air pressure-induced shifts; Speed dependence
OSTI Identifier: