  In this work, we measured the absorption by CO2+H2O mixtures from 2400 to
2600 cm-1 which corresponds to the spectral region beyond the nu3 band head of
CO2. Transmission spectra of CO2 mixed with water vapor were recorded with a
high-resolution Fourier-transform spectrometer for various pressure,
temperature and concentration conditions. The continuum absorption by CO2 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 CO2 as well as of the self- and CO2-continua of water vapor induced by
the H2O-H2O and H2O-CO2 interactions. The obtained results are in very good
agreement with the unique previous measurement (in a narrower spectral range).
They confirm that the H2O-continuum of CO2 is significantly larger than that
observed for pure CO2. This continuum thus must be taken into account in
radiative transfer calculations for media involving CO2+H2O mixture. An
empirical model, using sub-Lorentzian line shapes based on some
temperature-dependent correction factors chi is proposed which enables an
accurate description of the experimental results.
