Spectroscopic investigations of N₂(A³Σ_u⁺) metastables in the spatial ionisation growth in nitrogen

Abstract

The authors describe a spectroscopic technique to investigate the transport processes of electrons and the quenching processes of excited metastable molecules under the condition of non-self-sustained Townsend discharges. The technique is applied to pure N2, and N2 including NO as an impurity at E/N=282.5 Td and currents less than 10-9 A. The quenching factor of N2(A3 Sigma u+) metastable by NO, defined by (1-(density of N2(A3 Sigma u+) in N2 with NO)/(density of N2(A3 Sigma u+) in pure N2)), is measured as a function of total gas density from the emission spectrum both of the second positive bands of N2 and of the gamma system of NO. The spatial profile of N2(A3 Sigma u+) is also monitored and estimated by the emission of the gamma system. It will be noted that half of the N2(A3 Sigma u+) metastables are deactivated with only 20 PPM of NO at N=1.94*1017 cm-3 in the low pressure ionisation growth chamber. The results give a quantitative explanation for the rapid decrease of the secondary ionisation coefficient in N2 in the presence of small amounts of the impurity. Also the radiative lifetime and the self-quenching rate coefficient are estimated in the present experimental conditions.

Effects of high-speed airflows on a surface dielectric barrier discharge

“…The dominant cause for the breakdown voltage increase is the depletion of metastable states, which are purged out from one period of the voltage to the other by the flow. Indeed, optical emission spectroscopy measurements in figure 4 show that the dominant excited species in the plasma is the nitrogen A 3 + u metastable state, which has a lifetime of the order of 10 −2 s as given in [18].…”

Study on Surface Modification of Polymer Films by Using Atmospheric Plasma Jet Source

“…Therefore, it can be considered that the radical species are involved in the modification of the sample surface, that the internal energy of plasma is spent to produce NO x compounds in the air plasma jet source, and that the amount of radical atoms, N and O, is smaller than that in the N 2 or O 2 plasma jet source. 7) These might lead to the deterioration in the improvement of hydrophilicity for the air plasma.…”

Kinetics of ions and neutral active states in the afterglow and their influence on the memory effect in nitrogen at low pressures

“…Later, the N 2 (A 3 + u ) metastable states created during the discharge [44] were invoked to explain the memory effect obtained in the late afterglow. Meanwhile, many investigations have shown the decay of these metastable states in the afterglow period is very rapid by the following processes: (1) quenching by the ground state of nitrogen atoms with a rate constant 5 × 10 −11 cm 3 s −1 [45]; (2) quenching by the ground state nitrogen molecules with a rate constant 5 × 10 −16 cm 3 s −1 [46]; (3) energy pooling reaction of two N 2 (A 3 + u ) metastable states, given one N 2 (B 3 g ) with rate constant 3.2 × 10 −10 cm 3 s −1 [47]; (4) energy pooling reaction of two N 2 (A 3 + u ) metastable states, given one N 2 (C 3 u ) with rate constant 2.6 × 10 −10 cm 3 s −1 [48]; (5) quenching of N 2 (A 3 + u ) metastable states on the walls [49] with unit probability and with the time constant τ ∼ R 2 /5.76D A , where R is the tube radius and D A is the diffusion coefficient; and (6) radiative de-excitation with radiative lifetimes 2 s [50] so that the effective lifetime of the N 2 (A 3 + u ) metastable state is finally about 1 ms [51].…”