Excited Species in the Middle Atmosphere

Photolysis reactions produce a number of electronically excited species, (e.g., 0(1D)) which play an important role in the middle atmosphere. Some of these constituents are important because they are very reactive and can initiate chains of important free radical chemistry. Examples of such processes include 

A significant aspect of excited state chemistry, especially in the mesosphere and lower thermosphere, is the importance of fluorescence and chemiluminescence. Fluorescence is the rapid re-emission of absorbed photons  

In the process of chemiluminescence, the emitting particle is excited by chemical reactions rather than direct photon absorption  

Excited species can lose their energy by collision (or quenching) with other molecules. However, in the upper atmosphere, where the density of air molecules is relatively small and more high energy photons are available to produce excited species, many constituents fluoresce or chemiluminesce. Thus, photons of specific wavelengths are released, producing characteristic airglow emissions. Many of these emissions can also be used to deduce information about the concentrations of atmospheric species. Table 2.1 presents a summary of some of the more 

Lower state Excited state Radiative lifetime (s) A (nm) Name 

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Table 2.1 Emissions of Some Excited Species in the Middle Atmosphere...

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