Radiation spectroscopy in the study of the influence of a helium-nitrogen mixture composition on parameters of DC glow discharge and microwave discharge

Studies of plasma of different types of discharge in $\mathrm{He}$-$\mathrm{N_2}$ mixtures by the radiation spectroscopy technique are reviewed, and the main mechanisms of formation of emissive conditions are analyzed. The results of comparative study of the influence of the plasma composition on the radiation spectrum, translational temperature, and functions of distribution over rotational and vibrational levels in excited states of nitrogen molecule ions and nitrogen molecules in positive DC glow and in the electrode sheath of an inhomogeneous MW discharge in a $\mathrm{He}$-$\mathrm{N_2}$ mixture are described. An approach is developed which allows retrieving the nonequilibrium distribution of the atom and molecule population in excited states with accounting for the aliasing atomic lines and molecular bands of radiations. It is shown that simulation of radiation spectra $\mathrm{N}_2(C^3\Pi_u\to B^3\Pi_g)$, $\mathrm{N}_2(B^3\Pi_g\to A^3\Sigma^+_u)$, and $\mathrm{N}^+_2(B^2\Sigma^+_u\to X^2\Sigma^+_g)$ under assumption of the Boltzmann distribution of the nitrogen molecule and its ion over rotational levels satisfactorily describes the measured gas discharge radiation spectra. It is ascertain that the distribution of the nitrogen molecule population over the vibrational level in the $C^3\Pi_u$ state weakly differs from that calculated by the Boltzmann formula in both discharges, and the function of nitrogen molecule distribution over the vibrational levels $gv_B=3$–$12$ in the $B^3\Pi_g$ state noticeably deviates from the Boltzmann distribution.