Thermodynamics and transport properties of thermal plasmas: the role of electronic excitation

The role of electronic excited states in affecting the thermodynamic and transport properties of thermal plasma is investigated in the temperature range [300-100 000 K] and in the pressure range [1-10(3) atm] for hydrogen and [10(-2)-10(3) atm] for nitrogen. Thermodynamic functions have been calculated modelling in different ways the electronic levels of atomic species (ground-state, Debye-Huckel and confined-atom approximations). Frozen and reactive specific heats as well as isentropic coefficients are strongly affected by the electronic excitation whereas compensation effects smooth its influence on the total specific heat, i.e. the sum of frozen and reactive contributions. Higher-order approximations of the Chapman-Enskog method have been used to evaluate transport coefficients, including electronically excited states as separate species. The importance of a state-to-state approach to calculate transport coefficients is presented taking into account the strong dependence of transport cross sections on the principal quantum number. Results for hydrogen, nitrogen and air plasmas are widely discussed.