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

Abstract 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 (LIF), which effectively separates LIF from plasma emissions. We demonstrate this capability by distinguishing between plasma emission and LIF 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 µ s, 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.