Consistent thermodynamics for plasma-assisted combustion

Excited-state species are a vital component of plasma chemistry modeling. Many previous works have studied the reactions of excited-state species. In almost all of these studies, the thermodynamic properties of the excited states are obtained via a modification of the formation enthalpy. It is often assumed that the error introduced by this procedure can be neglected. However, this is not true when vibrational states are included in the chemical mechanism. Specifically, we find that the error in adiabatic flame temperature can be as high as 100 K, and the error in NO concentration is as large as 50%. In this work, we will demonstrate how to consistently compute the thermodynamic data for these species. Key in computing thermodynamic data for excited-state species is the realization that an excited state is a subset of a full molecule description. The main challenge then becomes the consistently distributing the internal states over individual species.