Dissociation of CO₂ by nanosecond discharge: TALIF - measurements of O-atoms density and fast gas heating.

As the world transitions to a carbon-free economy, we face the challenge of decisively curbing our production of greenhouse gases. Despite being discovered many decades ago, plasma chemistry has recently emerged as a credible technology for clean energy applications. The question is whether plasma-based solutions can provide a valuable alternative to existing thermal processes and compete with other novel gas conversion technologies. This work focuses on nanosecond pulsed plasmas in carbon dioxide - first, to measure the O-atoms density immediately after the nanosecond pulse by two-photon absorption laser induced fluorescence (TALIF), and second, to demonstrate how nanosecond plasma can provide a workbench for plasma chemistry in general. There exists two competing mechanisms of dissociation of carbon dioxide in low temperature plasma: vibrational pumping and dissociation by electron impact where the former is more efficient but yields less and the latter requires more energy but can provide bigger values of dissociation fraction. Vibrational pumping is typical for low values of reduced electric field (E/N = 50-100 Td, N here is a gas density) and electronic excitation and dissociation via excitation of electronically excited states is dominant at high values of reduced electric field (E/N > 100-200 Td). In plasma chemistry, G-factor is defined as energy (in eV/particle) required for a particular particle to form in a plasma under prescribed chemical conditions, or as its reciprocal value, number of particles produced when receiving a given amount of energy by the plasma (typically measured in units of particles/100 eV). Analysis of G-factor allows tailoring a more energy-efficient process. The talk will present a method of experimental analysis of G-factors using nanosecond moderate pressure discharges.