Electric field determination from intensity ratio of ${{\rm{N}}}_{2}^{+}$ and N₂ bands: nonequilibrium transient discharges in pure nitrogen

Abstract

We developed an extension of the spectrometric method to estimate a reduced electric field (E/N), which is applicable in nitrogen-containing plasmas. The method is based on the intensity ratio of the emission bands of the first negative system (FNS) of + N 2 and the second positive system (SPS) of N 2 . It uses the emission occurring in the wavelength interval 375-410 nm, which includes six SPS and two FNS bands. The choice of the spectral window is guided by much simpler acquisition and processing of experimental data than the SPS(0, 0) and FNS(0, 0) pair that is typically used. Following this idea, we construct a kinetic model for pure molecular nitrogen, which determines the population of the upper states responsible for the FNS and SPS emission. Moreover, we perform sensitivity analysis of the kinetic model, which allows us to reveal the most significant processes for the investigated intensity ratios. For these processes, we provide an in-depth review of the kinetic data that are available in the literature. We use the fact that the spectral window investigated contains bands to obtain three independent intensity ratios with sufficient signal-to-noise ratio ((FNS(0, 0)/ SPS(0, 2), FNS(0, 0)/SPS(1, 4), FNS(0, 0)/SPS(2, 5)), which are usable for more accurate electric field determination. We also provide analytical formulas representing intensity ratio dependencies on E/N. Furthermore, we focus on different spectrometric representations of FNS and SPS bands, which also affect the precision of E/N determination. We examine the FNS/SPS band profiles in terms of different rotational temperatures and instrumental functions. Finally, we propose a simple procedure that enables the use of bandhead intensities in the intensity ratio dependencies, thus avoiding the need to evaluate integral band intensities from the recorded spectra.

High-resolution electric field and temperature distributions in positive streamers

“…The calibration curves, relating the ratio of FNS (0-0) and SPS (2-5) emissions to reduced electric field strengths, for Paris [26] divided by a factor of 2 and Bílek [13,25] for synthetic air and nitrogen at 33 mbar.…”

“…The intensity ratio for these species is therefore valid for field strengths where both species are readily produced, but the mean electron energy of the EEDF is not so high that the sensitivity reduces, see the slope for the lines in Figure 5. The use of the intensity ratio method is limited by the fulfilment of the following conditions [25]. Firstly the electron impact excitation of N + 2 (B 2 Σ + u ) and N 2 (C 3 Π u ) states from level ] = 0 of the ground N 2 (X 1 Σ + g ) state should be dominant.…”

“…The ratio R(E/N) can be obtained by either using a Townsend discharge setup [26] or by using a kinetic model with appropriate kinetic data [25]. Within this work, we use the intensity ratio of the FNS (0-0) and SPS (2-5) to determine the electric field in synthetic air and pure nitrogen at 33 mbar.…”

“…Frontiers in Physics frontiersin.org are discussed in detail in [12,13,25]. The final uncertainty calculation of the calibration curves is now performed by Monte-Carlo-based uncertainty quantification, where rate constants were varied within the range as defined in the fourth column of Table 2.…”

Plasma-assisted agriculture: history, presence, and prospects—a review

“…In such a case, the state-of-the-art diagnostics of plasma filaments have to be applied during the treatment process with adequate spatio-temporal resolutions (a few micrometres in space and (sub)nanoseconds in time). The required diagnostics include the direct monitoring of the treatment 'morphology' through intensified charge-coupled device microscopic imaging [260,315] and the determination of basic plasma parameters via emission/laser-induced fluorescence (LIF)/two-photon absorption laser-induced fluorescence (TALIF) spectroscopy [225][226][227][316][317][318][319][320][321][322][323][324][325][326].…”