Recombination kinetics of atomic ions in dense low-temperature nonisothermal plasmas

The recombination kinetics of atomic ions is examined on the basis of a modified diffusion approximation including collisions of excited atoms with both electrons and neutrals. The relationship between the discrete and differential descriptions for theflux over excited states is analyzed for a transition to a quasicontinuous variation in the energy. It is established that the recombination coefficient can be found in the diffusion approximation with satisfactory accuracy by summing the corresponding coefficients of diffusion and dynamic friction. The three-body recombination coefficient $\alpha$ is calculated including both the elastic and dipole–dipole mechanisms for interactions of neutrals with bound electrons. Here the latter mechanism is accounted for in a more accurate manner than in the past and is seen to be important for the determination of $\alpha$ when $n_e/n_a \gtrsim 10^{-7}$. It is shown that for different ratios of the efficiencies of electron and atom quenching the dependence of a on the electron temperature $T_e$ varies between being proportional to $T_e^{-9/2}$ (when electron processes predominate) and $T_e^{-3/2}$ (when transitions resulting from collisions with atoms predominate).