We study the link which exists between microscopic (detailed) models for the evolution of the electronic configurations in a population of ions and the macroscopic (average ion) models. Rigorous asymptotics are presented in situations where they exist (large temperature; almost empty or almost full shells), and numerical simulations are presented.
"About the link between the detailed description of transitions in an ion and the average-ion models." Commun. Math. Sci. 7 (2) 471 - 488, June 2009.