Measurements of pure CO2 absorption in the 2.3-μm region are presented. The 3800–4700-cm−1 range has been investigated at room temperature for pressures in the 10–50-atm range by using long optical paths. Phenomena that contribute to absorption are listed and analyzed, including the contribution of far line wings as well as those of the central region of both allowed and collision-induced absorption bands. The presence of simultaneous transitions is also discussed. Simple and practical approaches are proposed for the modeling of absorption, which include a line-shape correction factor χ that extends to approximately 600 cm−1 from line centers.
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We present experimental results on the absorption by CO2-N2 mixtures in the 4.3 μm region. Measurements have been made in the 300–800 K and 0–60 bar ranges; these are in good agreement with previous determinations below 296 K. Frequency- and temperature-dependent factors χ are introduced in order to account for the subLorentzian behavior of the CO2 far line-wings. Their dependences on temperature are deduced from experimental results beyond the 4.3μm band-head in the 193–773 K range for both CO2-CO2 and CO2-N2 and fitted by simple analytical functions. Comparisons are presented between experimental and theoretical spectra on both the low- and high-frequency sides of the band (2100–2600 cm-1 range). It is shown that calculations using χ factors are inaccurate near line-centers at elevated pressures.
