We present, for the first time, shock-tube measurements of the absorption of infrared radiation by pure CO2 near 4 µm up to the temperature of 1200 K. The experimental values are in good agreement with previous determinations up to 800 K. These results demonstrate the interesting point of this new measurement technic and the investigated temperature and pressure ranges are extended toward those of the combustion media. Comparisons with calculations confirm the strongly sublorentzian behavior of the far wings of CO2 absorption lines; the accuracy of previously published models based on empirical corrections to the Lorentzian profile is also shown.
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Measurements of the absorption by pure CO2 in the 4.3 µm region are presented. They refer to the temperature of 291 K and densities in the 1–80 amagat range. Calculations based on the addition of Lorentzian contributions strongly overestimate the absorption since they do not account for line overlapping. The energy corrected sudden approximation (ECSA) is used to model line mixing within the impact approximation. The scaling parameters of this model are deduced from line-broadening data. This calculation strongly underestimates the absorption in the spectral region near the edges of the vibrational band, whereas it overestimates the absorption in the far wings of the lines. This is attributed to the impact approximation which does not account for the frequency dependence of the relaxation operator. This dependence is roughly determined from our results; it is in good qualitative agreement with the few corresponding available results
