Intensities and shapes of H ₂O lines in the near-infrared by tunable diode laser spectroscopy

The integrated intensities, self- and air-broadening coefficients of thirteen transitions of H ₂ ¹⁶O in the 11980-12260cm ^-1 region, belonging to the 2ν ₁+ν ₂+ν ₃ band, were measured. Using a tunable diode laser system, spectra were recorded at room temperature for a wide range of pressure (2-15Torr for pure H ₂O and 50-760Torr for H ₂O 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 H ₂O 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.