How do I interpret a flux quoted in cm⁻² s⁻¹ in atmospheric chemistry? I'm reading a paper about the atmospheric chemistry on Titan {1}. It quotes "column photochemical and loss rates" for various species in units of  $\mathrm{cm^{-2}s^{-1}}$. These figures are the overall rates at which these species are generated photochemically according to a model, and I would like to convert them into units of $\mathrm{mol/s}$ or $\mathrm{mol/s/m^2}$.

However, I don't know how to interpret the given units of $\mathrm{cm^{-2}s^{-1}}$. It feels like it should be something like CCs of gas produced per $\mathrm{cm}^2$ of the planet's surface area - but that would be $\mathrm{cm\,s^{-1}}$ rather than $\mathrm{cm^{-2}s^{-1}}$. No matter how I look at it I can't see where the $\mathrm{cm^{-2}}$ comes from - is anyone able to explain this?

{1} P. P. Lavvas et al. (2008) Planetary and Space Science 56, pp. 67-99.
The "strange" unit describes the photon flux, which is the number of photons (of unspecified wavelength) that hit an area (thus $\mathrm{cm^{-2}}$) in a time interval (thus $\mathrm{s^{-1}}$).


  It feels like it should be something like CCs of gas produced [&hellip;]


Not really. Not every photon leads to an excited state, not every excited state triggers a chemical reaction.