Kinetics of Ionization-Recombination of a Plasma and Population Density of Excited Ions. V. Ionization-Recombination and Equilibrium Plasma

Simple approximate formulas are proposed for the collisional-radiative ionization rate coefficient and recombination rate coefficient for hydrogen-like ions. These formulas are based on the continuation properties of various atomic quantities from the discrete states across the ionization limit to the continuum states. For an equilibrium plasma ionization ratio and population density distribution are discussed. The validity criterion for partial LTE (local thermodynamic equilibrium) is presented, which is much more stringent than Griem's criterion. The case of non-hydrogenic ions is briefly discussed.