Discharges Investigated by Laser Diagnostics*

Discharges in CO₂ are recently in the focus of intensive research, motivated by various applications such as CO₂ reduction, synthetic fuel generation, energy storage or in situ resource utilization on Mars. In all these applications, efficient dissociation of the CO₂ molecule and knowledge of its kinetics in non-equilibrium plasmas is required. CO₂/N₂ mixtures are also an important subject of study due to the presence of N₂ in waste gas streams. While many studies have been carried out with different reactor designs and models, often only the conversion rates and energy efficiency are reported. To deepen the understanding of the CO₂ kinetics pathways in such discharges, knowledge of both, the densities of excited states and of the plasma parameters is required. In this work, a ns-pulsed near-atmospheric pressure plasma jet operated in a CO₂/N₂ mixture is studied, which allows a temporal separation of the excitation and the subsequent V-V and V-T relaxation. The densities of rovibrationally excited states of CO₂ are measured with nanosecond resolution during the discharge and the afterglow by absorption spectroscopy using a quantum-cascade-laser (QCLAS). From these measurements, additional discharge parameters are extracted and compared with results from E-FISH measurements.