Measurements of H2O broadening coefficients of infrared methane lines

Abstract

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 80Torr and at 323 and 367K. Line broadening and shifting coefficients were retrieved from the measured spectra through fits using Voigt profiles. Values at room temperature (296K) 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.