Atmospheric gases, ionic reactions

In real-world systems, ranging from atmospheric droplets to flue-gas scrubbers, reactions take place over a wide range of pH, temperature, and ionic strength. Computer modeling incorporating the free radical chemistry of S02 autoxidation needs to be applied to these systems to identify gaps in our knowledge and determine which reactions deserve further study. These models should provide... 

The chemistry of gas-phase reactions, either in the interstellar medium or in stellar atmospheres, is mediated by the abundance of ions. These can be formed in several ways by cosmic-ray ionization, or by the direct photoionization of the atoms involved in the reactions with subsequent charge transfer to the molecules. Ionic reactions are generally exothermic and so occur efficiently at low temperature. In the presence of an ion, a neutral molecule or atom develops an induced dipole which increases its capture cross section. Thus the reactions occur quickly and lead to stable states, in addition to allowing the molecule to form in a radiatively unstable excited state which, upon decaying, radiates the energy of formation away from the site of the reaction. 

The volume fraction of the atmosphere occupied by aerosols in the form of solid or semisolid particles, cloud and fog droplets is always very small. However, aerosols are the sites of a rich chemistry at low and medium altitudes involving ionic, redox and surface reactions that would otherwise not take place [1]. They influence gas-phase chemistry acting as sinks of reactive species, transforming and sending back trace substances to the gas phase... 

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