Time-resolved optical diagnostics for plasma dissociation of CO2

Investigating non-equilibrium discharge plasmas requires reliable diagnostic methods that can account for the inhomogeneity and transient nature of pulsed discharges. In this thesis work, time-resolved optical diagnostic techniques have been developed to investigate these systems, focusing on nanosecond repetitive discharges employed for CO2 conversion. Collisional energy-transfer laser-induced fluorescence (CET-LIF) is a promising novel methodology to quantify the time evolution of the composition of a simple gas mixture. It exploits the impact of collisional processes on the LIF outcomes of a probe molecule (OH). For quantitative determinations, a new set of collisional rate constants of the OH(A2Σ+, v = 0, 1) manifold and their temperature dependence over a wide range has been measured. In addition to LIF spectroscopy, time-resolved optical emission spectroscopy (TR-OES) has been used to reveal the non-equilibrium characteristics of plasma discharges. The Second Positive System band of nitrogen has been used to infer the gas temperature evolution; the Stark broadening of the O triplet at 777 nm allowed to determine the electron density. Finally, the ratio of the C+ and C++ emission lines yielded information on the electron temperature evolution.