I've been able to find how to calculate the recombination rate for semiconductors as a function of the type of semiconductor (like silicon), the doping material, the concentration of the excess carrier and resistivity, and the model for recombination. However, I don't know about the recombination rate calculation for a gaseous plasma. Can a similar relationship be used to calculate the recombination rate of plasma, where the electrons would be more excited? I suppose that would have to assume that the plasma would be a semiconductor, while generally atmospheric gases are considered insulators, but otherwise I was wondering what calculation you apply for plasma of say, neon or nitrogen (not sure if it differs for thermally or electrically dominated plasma).
There are two types of recombination processes in plasma, three-body (collisional) and radiative (or photo-recombination). The distinction is based on what particle removes excessive momentum and energy when an ion and an electron recombine. In the three-body recombination it is another electron, in the radiative recombination it is a photon. A good starting point for this subject is the NRL Plasma Formulary, it contains main formulas and references. This is extracted from the Formulary: