Elementary Reactions and the Interpretation of Measurements of Chemically Reacting Non L.T.E. Plasmas

Abstract

Abstract-The "thermodynamic state" and the spatial-temporal evolution of the composition of chemically reacting plasmas are generally described by the Boltzmann or Pauli kinetic equations (balance equations for the transfer of particle densities, momentum, and energy for the different chemical species). Due to the numerous difficulties encountered when solving these coupled differential equations, simplifying assumptions are often introduced. The resultstherefore depend,ontheonehand,ontheelementaryreactions chosenforthemodelcalculations and,ontheother hand, on the cross-sections. Vice versa, the interpretation of both the thermodynamic state and the diagnostic measurements is dependent on the kind of elementary reactions introduced in the model.The dependence on the different atomic and molecular elementary reactions of the atomic (molecular) models adopted is demonstrated for some cases such as hydrogen, helium, highly ionized atoms, nitrogen, on the basis of a Maxwellian velocity distribution. As a refined step, deviations from a Maxwellian distribution should be taken into account. The laser is often used for plasma diagnostic purposes. The influence of the plasma state by a superimposed laser radiation field is briefly treated including photo-ionization and recombination stimulated by one and two laserphotons. Omission of these reactions can lead to erroneous interpretation of measurements. Some of the model calculations are compared with experimental results.