Computation of thermodynamic plasma properties: A simplified approach

An approximate method for calculating the electronic partition functions of atomic systems is reported. The method is based on the idea of combining a multitude of atomic energy levels into two or three grouped levels. Dimensionless formulation suitable for practical calculations is presented. Application to real systems shows that two grouped levels are enough to model hydrogen-like and noble gas atoms, whereas three grouped levels are required to describe atoms with low lying excited states. Two methods for the calculation of degeneracy and energy values of the grouped levels are investigated. Representative mono-atomic LTE plasma properties calculations are reported. The results agree with accurate computations using partition functions that include several thousands energy levels.