The water vapor self-continuum absorption at room temperature in the 1.25 µm window

The water vapor foreign continuum in the 8100-8500 cm−1 spectral range

“…Although a number of significant deviations were evidenced (e.g. the MT_CKD self-continuum in its 3.0 version was underestimated by a factor 5 to 10 near the centre of the 2.3 µm window [11][12][13]16]), the measurements roughly validated the MT_CKD values up to 8000 cm -1 [17]. Considering the long-range spectral extrapolation of this semi-empirical model, this achievement deserves to be underlined.…”

“…The experimental approach is mostly the same as described in Ref. [17] for the selfcontinuum determination, except that the amplitude of the pressure ramps is much larger (up to 1 atm).…”

“…As in Ref. [17], the CRDS absorption signal is measured for series of pressure ramps at several fixed spectral points (from 5 to 8 depending on the gas mixture) selected in spectral microwindows minimizing the resonance line contribution (in fact, in the considered spectra region, the resonance line contribution is always large and remains the dominant contribution of the water-related absorption -see below). The chosen spectral points are part of the 29 spectral points used in Ref.…”

“…Since 2013, we are involved in a long-term experimental project aiming to characterize the water vapor continuum mostly in the near-infrared windows where previous data were very scarce and reported with large uncertainties. Due to the weakness of the continuum signal, the measurements are performed using cavity enhanced absorption spectroscopy techniques (mostly cavity ring down spectroscopy -CRDS-but also optical feedback cavity enhanced absorption spectroscopy -OFCEAS) [7][8][9][10][11][12][13][14][15][16][17]. The cross-section derived at specific spectral point values are systematically used for validation tests of the current version of the MT_CKD model.…”

On the nature of sub-THz continuum absorption in CO2 gas, its mixture with Ar, and in pure water vapor

“…An obvious drawback of the model is its inherent inability to fully take into account water dimers, whose spectral bands do not coincide with monomer bands. 25,26 In order to correctly model the continuum, it is necessary to construct a physically wellgrounded model.…”