Experimental and theoretical studies of the electron temperature in nitrogen afterglow

In this paper, results of joint experimental and theoretical studies of the electron temperature in nitrogen afterglow at pulse-periodical excitation are presented. Electron energy distribution function (EEDF) in an afterglow of a pulsed direct current discharge has been measured by means of a time-resolved Langmuir probe technique. Electron concentration, vibrational temperature, and population of lower metastable electronic state of N₂ molecules have also been experimentally estimated at different delays after the discharge pulse. The results show that electron temperature in afterglow decreases with time, while the vibrational temperature remains almost constant. The EEDF has been calculated numerically from a steady-state Boltzmann equation, taking into account electron-electron collisions as well as superelastic collisions with vibrationally and electronically excited molecules. The vibrational distribution function was found numerically by solving a system of kinetic equations. Calculations show that the vibrational distribution function weakly varies within a cycle and is controlled by an average discharge power. Electron temperature in nitrogen afterglow for given populations of vibrational levels and of lower electronic level essentially depends on the electron concentration. Finally, a comparison of the theoretical and experimental results is performed.