A complete set of line parameters for CH3Br in the 10-μm spectral region

Using FT spectra (Bruker IFS 120, unapodized FWHM resolution ≈0.001cm-1) of methyl bromide CH3Br, absolute line positions and intensities, as well as self- and N2-broadening coefficients have been measured for about 1200 lines, between 880 and 1050cm-1, in the ν6 band of both 12CH379Br and 12CH381Br isotopologues. An absolute wavenumber calibration has been performed using the frequencies of the ν2 band of NH3. A multispectrum fitting procedure has been used to retrieve simultaneously the line parameters from six experimental spectra recorded at different pressures of CH3Br and N2. Average absolute accuracies of the measurements have been estimated to be equal to ±0.0002cm-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-μm spectral region. Measured line intensities have been analyzed in order to predict the intensities for the whole ν6 band. The J and K dependences of the self- and N2-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 N2-broadening coefficients for which clear J and K dependences have been observed and modeled. A complete line list containing line positions, intensities, self- and N2-broadening coefficients has then been generated for atmospheric purposes from 820 to 1120cm-1.