Intensities and shapes of H2O lines in the near-infrared by tunable diode laser spectroscopy

The integrated intensities, self- and air-broadening coefficients of thirteen transitions of H216O in the 11980-12260 cm−1 region, belonging to the 2ν1+ν2+ν3 band, were measured. Using a tunable diode laser system, spectra were recorded at room temperature for a wide range of pressure (2-15 Torr for pure H2O and 50-760 Torr for H2O in air). Line parameters were adjusted from experiments using three line-shape models: the Voigt profile (VP), the (hard collision) Rautian profile (RP) and the speed dependent Voigt profile (SDVP). The results show that the RP and SDVP are in better agreement with measurements than the VP and that they lead to larger values of the line parameters (about 5% for the line broadening, and 0.8% for the line intensity). Comparisons of the present results with HITRAN 2008 [Rothman et al., JQSRT 2009, 110:533-72] show that the HITRAN intensities of the studied lines are overestimated by about 9.4%, suggesting a more complete study of the H2O line parameters in the considered region. The Dicke narrowing and speed dependence parameters deduced from this work are also presented and discussed, demonstrating the need for a more refined line-shape model.

► Spectra of 13 NIR lines of H216O have been measured using a tunable diode laser system. ► Several line shape models have been used to determine the line parameters. ► Intensities and broadenings obtained by the Voigt model are underestimated by 0.8 and 5%. ► The measured intensities are 9% smaller than those in HITRAN 2008 for the studied lines.