Population kinetics from a two-level atomic model

This thesis investigates population kinetics in plasmas using the two-level model. The population ratio between energy levels is derived and analyzed with respect to excitation energy,
electron temperature, and electron density. The results show a complex relationship between
excitation energy and electron temperature, although the model converges to intuitive limits
in extreme parameter regimes. The study further examines effective temperatures in non-local
thermal equilibrium plasmas by comparing Hansen’s[1] and Busquet’s [2] formulations, showing
agreement in high-density and high-temperature limits, but deviations at lower values. Additionally, the influence of the Gaunt factor on collisional-radiative rates is explored, with Mewe’s [3]
approximation found to yield consistently higher values than the Younger-Wiese [4] model across
relevant parameter ranges. Finally, the model is extended to three levels, considering both interacting and non-interacting excited states. The non-interacting case reduces to two independent
two-level systems, whereas the interacting case requires more complex coupled equations. These
results demonstrate both the strengths and limitations of reduced models in capturing plasma
population dynamics, providing insight for applications in astrophysics and nanolithography.