2D imaging of atomic oxygen reaction dynamics after a nanosecond pulse discharge using Light-field Amplitude Control

Plasma-assisted technologies are rapidly advancing and are set to play a crucial role in the green transition. One challenge in this development, specifically tied to laser-based plasma diagnostics, is the presence of interfering plasma-induced emissions, such as the de-excitation of naturally excited species, which can complicate the detection of laser-induced signals. Successfully differentiating between the two would unlock new measurement possibilities within plasma and its applications. This paper presents an adaptation of Light-field Amplitude Control (LAC), a novel approach to two-photon atomic laser-induced fluorescence, which effectively separates laser-induced fluorescence from plasma emissions. We demonstrate this capability by distinguishing between plasma emission and laser-induced fluorescence in the afterglow of a nanosecond pulsed discharge in atmospheric pressure oxygen gas. Utilising LAC, we present single-shot 2D maps of ground state atomic oxygen distributions at different delays after discharge. Additionally, we report on the temporal dynamics of ground-state atomic oxygen concentration following the discharge, quickly growing until peaking at 2.8 μs, information that was previously unavailable due to interfering plasma emissions. We have also analysed the consumption of atomic oxygen, presenting a 2D map of consumption dynamics and chemical lifetime. Directly, these results will lead to a better understanding of plasma chemistry in oxygen gas, especially the rapid growth phase, but the adaptation of LAC to general plasma diagnostics will enable the extraction of a whole host of new information through the removal of plasma emission.