Barrier discharges in CO₂ – optical emission spectra analysis and <i>E/N</i> determination from intensity ratio

Abstract Barrier discharges in CO 2 are investigated using optical emission spectroscopy and electrical measurements, with the support of spatially one-dimensional fluid modelling. This study focuses on a sinusoidally driven atmospheric pressure Townsend discharge (APTD) and a single- and multi-filament barrier discharge at atmospheric pressure. The spectra of weak CO 2 barrier discharge emission in UV–vis–NIR range are recorded. The optical emission of selected vibrational spectral bands is analyzed and the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>E</mml:mi> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> </mml:math> in barrier discharges is determined using the developed intensity ratio method and kinetic data available in the literature. The technique of time-correlated single-photon counting is used to obtain the necessary sub-nanosecond temporal resolution and high signal sensitivity for the single-filament experiment. After the necessary calibration, the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>E</mml:mi> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> </mml:math> of 330 Td is measured in the barrier discharge streamer head. This is coherent with the results of numerical modelling. The <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>E</mml:mi> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> </mml:math> determined in APTD has a value of 110 Td, which agrees within 10% with the results of the electrical equivalent circuit model. The uncertainties coming from kinetic data and the low sensitivity of some rate coefficient ratios complicate the easy and broad utilization of the method. Future steps are therefore proposed, including uncertainty quantification and sensitivity analysis of the simplified model and necessary synthetic spectra fitting.