Optical gain in halogen atom recombination reactions

The radiative channel of halogen atom recombination reactions is discussed using experimental data. It is found that various types of population of excited electronic states are formed during recombination. Calculations are made of the optical amplification cross sections for various transitions. It is found that for recombining atom concentrations of $1-5\cdot10^{18}$ cm${}^{-3}$ at temperatures not exceeding 600-800 K, an optical gain of the order of $10^{-3}$cm${}^{-1}$ may be achieved in the near infrared.