A complete set of line parameters for [formula omitted] in the 10- [formula omitted] spectral region

Abstract

Using FT spectra (Bruker IFS 120, unapodized FWHM resolution ≈ 0.001 cm - 1 ) of methyl bromide CH 3 Br , absolute line positions and intensities, as well as self- and N 2 -broadening coefficients have been measured for about 1200 lines, between 880 and 1050 cm - 1 , in the ν 6 band of both 12 CH 3 79 Br and 12 CH 3 81 Br isotopologues. An absolute wavenumber calibration has been performed using the frequencies of the ν 2 band of NH 3 . A multispectrum fitting procedure has been used to retrieve simultaneously the line parameters from six experimental spectra recorded at different pressures of CH 3 Br and N 2 . Average absolute accuracies of the measurements have been estimated to be equal to ± 0.0002 cm - 1 for line positions, to ± 5 % for line intensities, and to ± 5 –10% for broadening coefficients. A theoretical treatment of measured line positions permitted a prediction of positions and assignments for the whole 10- μ m spectral region. Measured line intensities have been analyzed in order to predict the intensities for the whole ν 6 band. The J and K dependences of the self- and N 2 -broadening coefficients have been observed and modeled. These measurements improve the precision of wavenumbers and line intensities previously obtained and lead us, for the first time, to a complete set of self- and N 2 -broadening coefficients for which clear J and K dependences have been observed and modeled. A complete line list containing line positions, intensities, self- and N 2 -broadening coefficients has then been generated for atmospheric purposes from 820 to 1120 cm - 1 .