Ions with small solvation spheres of 1, 2, 3... solvent molecules can be studied in the gas phase and then extrapolated to bulk solution.
[3] RRKM theory is used to compute simple estimates of the unimolecular ion decomposition reaction rates from a few characteristics of the potential energy surface.
Associative ionization is a gas phase reaction in which two atoms or molecules interact to form a single product ion.
Associative Penning ionization can also occur: There are many important dissociation reactions that take place in the gas phase.
CID (also called collisionally activated dissociation - CAD) is a method used to fragment molecular ions in the gas phase.