= Solution
For one specified channel, the <photolysis rate coefficient> is
$$
J(z)=\int F_\lambda(z)\,\sigma_\lambda(T)\,\Phi_\lambda(T)\,d\lambda.
$$
It depends on spectral <actinic flux>, absorption <cross section>, and channel <quantum yield>. Solar zenith angle, season, overhead absorbers, clouds and <aerosol> scattering affect the photon field; branching and collisional quenching affect the chemical yield. Absorption alone does not guarantee the desired dissociation.
\b[Curve A is <oxygen> <photodissociation>; curve B is <ozone> <photodissociation>.] Molecular <oxygen> needs relatively short-wavelength ultraviolet photons, which are strongly screened at lower altitudes, so its rate increases steeply with height. <Ozone> can dissociate using longer wavelengths that penetrate much further, producing the much larger, less height-sensitive rate shown by B. The plotted quantity is a first-order coefficient with units $\mathrm{s^{-1}}$, rather than a bimolecular <rate constant>.
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