Model, software, and database for computation of line-mixing effects in infrared Q branches of atmospheric CO₂: II minor and asymmetric isotopomers

The influence of line-mixing on the shape of infrared Q branches of minor isotopomers of CO₂ is studied for the first time. Laboratory spectra of isotopically enriched CO₂-N₂ mixtures have been measured in the 15 μm region at the temperatures of 200 and 300 K for total pressures between 1 and 10 atm. Comparisons with measurements for the v₂ and (v₁-v₂)₁ Q branches of the six isotopomers ((16, 17, or 18))O-¹²C-O((16, 17, or 18)) demonstrate the quality of the theoretical approach presented in the preceding paper (Part I). The model is used to generate a set of numerical data (available by ftp) for the prediction of absorption by ¹⁶O¹²C¹⁸O, ¹⁶O¹²C¹⁷O, ¹⁶O¹³C¹⁸O, ¹⁶O¹³C¹⁷O, and ¹⁷O¹²C¹⁸O infrared Q branches under atmospheric conditions; this database completes that proposed in the preceding paper and now includes 271 bands considering the eight most abundant CO₂ isotopomers. Its quality is tested by comparisons with atmospheric limb emission measured by a balloon-borne high resolution Fourier transform instrument. The v₂ Q branches of ¹⁶O¹²C¹⁶O, ¹⁶O¹³C¹⁶O, ¹⁶O¹²C¹⁷O, and ¹⁶O¹²C¹⁸O recorded above Alaska have been used. This shows that line mixing has significant effects, even for minor isotopomers, and is correctly accounted for by the model and data proposed.