Improvements to the RADIOM non-LTE model

In 1993, we proposed the RADIOM model [M. Busquet, Phys. Fluids 85 (1993) 4191] where an ionization temperature Tz is used to derive non-LTE properties from LTE data. Tz is obtained from an “extended Saha equation” where unbalanced transitions, like radiative decay, give the non-LTE behavior. Since then, major improvements have been made. Tz has been shown to be more than a heuristic value, but describes the actual distribution of excited and ionized states and can be understood as an “effective temperature”. Therefore we complement the extended Saha equation by introducing explicitly the auto-ionization/dielectronic capture. Also we use the SCROLL model to benchmark the computed values of Tz.