Atmospheric pressure Townsend discharge in pure nitrogen—a test case for N2( A3Σu+,v ) kinetics under low E/N conditions

Abstract

Abstract This work investigates the kinetics of the N2( A 3 Σ u + , v ) state in the atmospheric-pressure Townsend discharge (APTD) operated in a barrier discharge setup in pure nitrogen. To understand the complex nature of the N2( A 3 Σ u + , v ) state we have developed a detailed state-to-state vibrational kinetic model of N2 applicable mainly at low reduced electric fields ( < 200 Td). The kinetic model benefits from the determination of the electric field and the electron density profile using the equivalent electric circuit analysis. The knowledge of both parameters significantly reduces the number of free parameters of the model and thus improves the accuracy of kinetic predictions. The results of the kinetic model are compared with the measured emission spectra of the second positive system and the Herman infrared system of N2. The use of the sensitivity analysis method leads to a better understanding of the role of specific elementary processes in the APTD mechanism and also to the determination of the density of the two lowest vibrational levels of N2( A 3 Σ u + ), which varies between 1012 and 1014 cm−3 depending on the applied voltage. The determination is important, because the two lowest vibrational levels of N2( A 3 Σ u + ) are considered to play an important role in the secondary emission of electrons from dielectric surfaces. This work shows that the complex state-to-state kinetic modeling in combination with the phase-resolved emission spectroscopy is the key to a better understanding of the processes responsible for establishing and sustaining the APTD mechanism in nitrogen.