Time evolution of atomic nitrogen density in pure-nitrogen-pulsed barrier discharge at sub-atmospheric pressure

Abstract

Ground state atomic nitrogen N(2p34S) was analyzed using two-photon absorption laser-induced fluorescence (TALIF) in sub-atmospheric pressure nitrogen pulsed barrier discharge under needle-to-hemisphere electrode configuration. By reducing the pressure from 90 to 30 kPa, the discharge form transitioned from multiple filaments to a single column, improving the reacting region uniformity. The TALIF measurement revealed that the amount of atomic nitrogen near the needle anode increased over tens of microseconds after the discharge, and this N-production during afterglow was enhanced by reducing the pressure. Reducing the pressure from 90 to 30 kPa extended the half-life period of atomic nitrogen near the anode by 350 μs, while maintaining the peak amount of atomic nitrogen. The lifetime extension with the same amount of atomic nitrogen helped improving the chemical activity near the anode. The origin of the N-production during afterglow was not identified as a single factor, but its time constant indicated the contribution of N(2P) quenched by the ground state atomic nitrogen, along with the quenching of N(2D), which was previously considered as a major source of afterglow production of the ground state atomic nitrogen. Under 30 kPa, higher discharge energy resulted in faster and larger amount of atomic nitrogen production during afterglow, which indicates the involvement of highly excited particles including metastable atomic nitrogen. In contrast, the decay rate of atomic nitrogen did not depend on the discharge energy. This suggests that the increasing discharge energy broadens the N-productive region while maintaining the local N density.