Measurements and modeling of absorption by CO 2 + H 2 O mixtures in the spectral region beyond the CO 2 ν 3 -band head

Abstract In this work, we measured the absorption by CO 2  + H 2 O mixtures from 2400 to 2600 cm −1 which corresponds to the spectral region beyond the ν 3 band head of CO 2 . Transmission spectra of CO 2 mixed with water vapor were recorded with a high-resolution Fourier-transform spectrometer for various pressure, temperature and concentration conditions. The continuum absorption by CO 2 due to the presence of water vapor was determined by subtracting from measured spectra the contribution of local lines of both species, that of the continuum of pure CO 2 as well as of the self- and CO 2 -continua of water vapor induced by the H 2 O-H 2 O and H 2 O-CO 2 interactions. The obtained results are in very good agreement with the unique previous measurement (in a narrower spectral range). They confirm that the H 2 O-continuum of CO 2 is significantly larger than that observed for pure CO 2 . This continuum thus must be taken into account in radiative transfer calculations for media involving CO 2 + H 2 O mixture. An empirical model, using sub-Lorentzian line shapes based on some temperature-dependent correction factors χ is proposed which enables an accurate description of the experimental results.