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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The shapes of the extreme wings of self-broadened CO2(lines have been investigated)in three spectral regions near 7000, 3800, and 2400 cm-1. Absorption measurements have been made on the high-wavenumber sides of band heads where much of the absorption by samples at a few atm is due to the extreme wings of strong lines whose centers occur below the band heads. New information has been obtained about the shapes of self-broadened CO2 lines as well as CO2 lines broadened by N2, O2, Ar, He, and H2. Beyond a few cm-1 from the line centers, all of the lines absorb less than Lorentz-shaped lines having the same half-widths. The deviation from the Lorentz shape decreases with increasing wavenumber, from one of the three spectral regions to the next. The absorption by the wings of H2- and He-broadened lines is particularly low, and the absorption decreases with increasing temperature at a rate faster than predicted by existing theories.
