A thermodynamic model for determination of the vibrational temperature in non thermal plasmas

A gaseous plasma in a non-local thermodynamic equilibrium (NLTE) can be characterized by the thermal disequilibrium Te ≠ Tex ≠ Tvib ≠ Trot ≠ Th, where Te and Th are respectively the translational temperatures respectively for the free electrons and heavy species, and Tex, Tvib, Trot are the internal temperatures respectively associated with the electronic, vibrational and rotational excited states of the species in the plasma. The accurate knowledge of these temperatures is crucial if one wants to determine for example the composition of a NLTE plasma or, more generally, its physical properties like thermal conductivity or heat capacity. To the best of our knowledge, even if one gets the assumptions Te≈Tex and Trot≈Th, no theory allows nowadays to evaluate Tvib which should be considered like a third free parameter of the current NLTE plasma models and which is fixed usually at Th or Te^{2, 3}.