The far wing shapes of CO2 ν3 band in infrared absorption spectra were calculated accounting for line mixing and finite collision duration effects. The result shows that the impact approximation can be used for the rough estimate of absorption intensity in the far wing region. This approach was used for H2O absorption estimate in the 8–12 μm atmospheric window. According to our calculations the H2O monomer absorption could be responsible for the part of absorption depending on the air pressure. However, the part of absorption depending on H2O pressure squared can hardly be explained in the frame of a model presupposing collisions between monomer molecules.
