Ro-vibrational kinetics in CO₂-N₂ ns pulsed discharge

The vibrational kinetics of the molecules in discharges in pure CO2 gas and its mixtures with other gases are of particular interest for a number of fields. Understanding the processes involving excited molecules is a challenging task due to the complex reaction pathways that often cannot be separated. Repetitively pulsed ns discharges offer unique possibility to introduce the high degree of vibrational excitation provided by the plasma electrons while keeping the reactions due to electron impact and molecular collisions apart through the separation of time scales. This advantage is used for studying the ro-vibrational kinetics of the CO₂ molecules in a mixture with N₂ at a pressure of 150 mbar. The temporal evolution of selected ro-vibrational states of CO₂ are obtained via ns-resolved tunable laser absorption in the mid-infrared region. The information on the temperatures for the various vibrational and the rotation modes is combined with measurements of the discharge current, voltage and electric field to provide information on the excitation behaviour of the CO₂ molecules. The efforts are supported by analytical models that provide explanations for the observed trends with varying mixture ratios of the CO₂ gas into the N₂.