Determination of N2(A3 u ) metastable density produced by nitrogen streamers at atmospheric pressure: 2. Experimental verification

A newly developed spectrometric method presented in a previous paper was applied to determine absolute densities of the N 2 ( A 3 Σ u + ) metastables produced by nitrogen streamers at atmospheric pressure. Primary streamers were generated in high-purity nitrogen with quantified NO traces employing very short high-voltage pulses in a coaxial wire–cylinder electrode geometry. The post-discharge formation of the N 2 ( C 3 Π u , C '' 5 Π u ), states was tracked and the evolution of the N 2 ( A 3 Σ u + ) species was inferred through the time dependence analysis of band intensities of the second positive N 2 ( C 3 Π u → B 3 Π g ) and Herman infrared N 2 ( C '' 5 Π u →{ A }' 5 Σ g + ) systems. The post-discharge evolution of the NO( A 2 Σ + ) state was monitored through the band intensities of the NO-γ( A 2 Σ + → X 2 Π) system. The concentration of N 2 ( A 3 Σ u + ) metastables was determined by analysing the time evolutions and relative intensities of NO and N 2 emissions driven by pooling and resonant energy transfer reactions. The highest N 2 ( A 3 Σ u + ) concentrations (∼5 × 10 14 cm −3 ) were found close to the central wire anode during early post-discharge time (∼1 μs).