We demonstrate a novel approach for the direct formation of nitrogen dioxide (NO \(_2\) ) in a supercritical nitrogen–oxygen mixture using laser-produced plasma. By tightly focusing a nanosecond laser pulse into the dense fluid, we generate a high electron density plasma that enables chemical reactions not accessible under ambient conditions. Optical emission and absorption spectroscopy confirm the in-situ formation of NO \(_2\) , and parametric investigations reveal that the yield is highly sensitive to the plasma characteristics and gas composition. These findings demonstrate the potential of using plasma as a compact and selective chemical microreactor in dense media, opening new possibilities for on-demand molecular synthesis in extreme environments such as space exploration.
