LINE MIXING EFFECTS IN IR Q BRANCHES OF $CO_{2}$. A DATABASE FOR ATMOSPHERIC SPECTRA COMPUTATIONS

Abstract

Line mixing effects in $CO_{2}$ infrared Q branches are studied both experimentally and theoretically. The model used is based on the Energy Corrected Sudden (ECS) Approximation. Its parameters for $CO_{2}-O_{2}$ and $CO_{2}-N_{2}$ mixtures have been determined. in the 200-300 K temperature range, from fits of absorption in the $(\nu_{1}-\nu_{2}){I}$ Q branch. The quality of the theoretical approach is demonstrated by comparisons with many (about 200) laboratory spectra: these include 8 Q branches of various symmetries as well as absorption by minor isotopomers. The model is then used to generate a set of numerical data for the computation of line-mixing effects in atmospheric $CO{2}$ Q-branches. This database, which includes all bands of significant absorption in the atmosphere for the 8 more abundant isotopomers, is available by ftp. Its validity is tested by comparisons with numerous stratospheric spectra recorded by balloon borne instruments. Bands of various symmetries and isotopomers are used, demonstrating the quality of the model and data.