Absorption of Radiation by Atmospheric Gases

The total photolysis rate of A is the integral of this expression over all possible wavelengths 

The quantity in brackets has already been identified as the first-order photolysis rate constant  

The integral in (4.39) is often approximated for computational purposes by a summation over small wavelength intervals 

FIGURE 4.9 (a) Solar spectral irradiance at the top of the atmosphere and at sea level. Shaded regions indicate the molecules responsible for absorption. Absorption spectra for (b) molecular oxygen and ozone, (c) water vapor, and (d) the atmosphere, expressed on a scale of 0-1. 

Similar arguments hold for ozone however, nitrogen and oxygen are symmetric and thus are not strongly affected by radiation above 400 nm. The C02 molecule is linear but can easily be bent, leading to an induced dipole moment. A transverse vibrational mode exists for C02 at 15 pm, just -where the Earth emits most of its infrared radiation. 

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