Departure from statistical equilibrium in nitrogen arc plasma

Using a stationary homogeneous hypothesis, a collision radiative model (CRM) is developed for nitrogen plasma. The number densities of the ground and the excited levels of nitrogen are calculated as a function of temperature T(K) and electron number density ne(cm−3). To quantify departure from statistical equilibrium, Sahaʹs decrement bj is introduced for each level j,j=1,2, …, 22. Also the departure from the Boltzmann ratio which is characterized by the quantity aj is discussed. The calculations have been performed for the optically thin case. The resonance radiation absorption has been also taken into account and has been included in the rate equations by means of an escape factor Λr. Finally, the influence of heavy particle collisions on the population densities of excited atomic levels has been discussed.