A novel collisional radiative model with a numerical bottom and an analytical top

A cut-off procedure for numerical collisional radiative (CR) models is developed and is based on knowledge of the excitation flow in the collision-dominated part of an atomic system as revealed by analytical models. This new cut-off technique makes it possible to reduce the number of levels in a numerical CR-model drastically in comparison with the older, numerical cut-off technique used by Bates et al, in which the truncation level was demanded to be in Saha equilibrium. The model is applied to an ionizing and recombining argon plasma as an example of a more general technique which can also be applied to other atomic systems. The results are in good agreement with the analytical top model developed previously in our group and also with the experiments and numerical calculations of Vl ek and Pelikán.