Measurements of H2O broadening coefficients of infrared methane lines

•High resolution FTS spectra of CH4 diluted in H2O were recorded.•H2O-broadening and shifting of 76 infrared CH4 lines were measured.•H2O-broadenings of CH4 lines are, on average, 34% larger than those for dry air.

H2O-broadening and shifting coefficients of 76 ro-vibrational transitions of methane in the mid-and near-infrared regions were measured for the first time. For this, eight spectra of methane diluted in water vapor were recorded with a high resolution Fourier Transform spectrometer for pressures ranging from 20 to 80 Torr and at 323 and 367 K. Line broadening and shifting coefficients were retrieved from the measured spectra through fits using Voigt profiles. Values at room temperature (296 K) were then deduced and compared with those of dry air. The results show that H2O-broadenings of methane lines are, on average, 34% larger than those for dry air.