Electronic Excitation and Thermodynamic Properties of High Temperature Gases

Different cut-off criteria of partition functions have been utilized in order to evaluate the con­tribution of electronic excitation to thermodynamic properties of high temperature gases (5000 °K to 35 000 °K, 10 -10 atm). It is shown that properties of single species are strongly affected by the cut-off criterion adopted, i. e. the contribution of electronic excitation to these properties is important. It is also shown that the reported absence of this contribution to total enthalpies and specific heats of plasmas is the result of an almost complete compensation between "reactional" and "frozen" terms which are all dependent on electronic excitation.