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This work is the first of two companion papers devoted to the kinetic modelling of low-pressure DC flowing discharges in - mixtures. While the present paper is mainly concerned with bulk discharge processes, the second one investigates surface processes involving dissociated N and H atoms, which are essential to understand the discharge properties. The global model combining bulk and surface processes as described in these two papers is self-contained in the sense that the sole input parameters it requires are those that can externally be chosen in experiments, namely: total gas pressure, radius and length of the discharge tube, discharge current, gas flow rate and initial gas temperature and composition (e.g., the relative hydrogen concentration X in the binary mixture at the discharge inlet). For a given set of input parameters, this model enables one to calculate the following bulk plasma properties as a function of the axial coordinate z : concentration of , , NH, , molecules and N, H atoms in the ground electronic state; population in the electronically excited states , (an effective high Rydberg state) and ; concentration of the ions , , , , , and ; vibrational level populations of and molecules; electron density , mean kinetic energy , characteristic energy and drift velocity ; discharge sustaining electric field E ; average gas temperature across the tube T and wall temperature . The calculations are compared with data from different experiments in pure and discharges (measurements of electric field as a function of current and pressure) and in - discharges (measurements of relative changes in the electric field and the , concentrations as a function of the percentage). From the comparison to experiment, rate coefficients for associative ionization upon collisions between two excited molecules and deactivation of and by H atoms have been estimated from the model.
Gordiet︠s︡ et al. (Sat,) studied this question.