The Spatial Resolution Effect of N₂/O₂ on Atmospheric Pressure Ar Plasma Jet

The atmospheric pressure low-temperature plasma jet (APPJ) can generate a wide variety of excited and active particles, with broad application prospects. Due to the strong spatiotemporal distribution characteristics of particles, the physical and chemical properties of plasma jets can be adjusted by changing the type and ratio of working gas, which is crucial for improving jet treatment efficiency and achieving specific treatment effects. This article innovatively analyzes the variations in the spatial distribution, intensity distribution, and activation region distribution of short-lived active substances that are crucial in the application of plasma jets under different gas backgrounds. Under the context of multiple variables, the physical characteristics of the plasma jets are comprehensively analyzed. The results show that the addition of N2 and O2 will weaken the discharge current and power, especially oxygen. After doping with 1% nitrogen, the jet length remains basically unchanged, but after doping with 1% oxygen, the jet length sharply decreases. Most active substances are concentrated at the nozzle of the jet pipe. The activation region of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {OH}(\mathrm {A}^{2}\Sigma ^{+}\to \mathrm {X}^{2}{\Pi })$ </tex-math></inline-formula> is significantly lower than that of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {N}_{2}(\mathrm {C}^{3}\Pi _{\mathrm {u}}\to \mathrm {B}^{3}\Pi _{\mathrm {g}})$ </tex-math></inline-formula>. As the N2 content increases from 0% to 1%, the activation region of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {OH}(\mathrm {A}^{2}\Sigma ^{+}\to \mathrm {X}^{2}\Pi)$ </tex-math></inline-formula> decays from 17 to 12 mm and the activation region of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {N}_{2}(\mathrm {C}^{3}{\Pi }_{\mathrm {u}}\to \mathrm {B}^{3}\Pi _{\mathrm {g}})$ </tex-math></inline-formula> remains unchanged, but the intensity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {N}_{2}(\mathrm {C}^{3}\Pi _{\mathrm {u}}\to \mathrm {B}^{3}\Pi _{\mathrm {g}})$ </tex-math></inline-formula> spectral line rises rapidly. As the O2 content increases from 0% to 0.1%, the activation region of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {OH}(\mathrm {A}^{2}{\Sigma }^{+}\to \mathrm {X}^{2}{\Pi)}$ </tex-math></inline-formula> has decayed below 10 mm. The intensity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {N}_{2}(\mathrm {C}^{3}{\Pi }_{\mathrm {u}}\to \mathrm {B}^{3}\Pi _{\mathrm {g}})$ </tex-math></inline-formula> spectral extremely reduced by 48%. The increase in N2 content will lead to an increase in vibration and rotation temperature, while O2 is the opposite. From the axial spatial distribution, the vibrational temperature does not change much, but the rotational temperature decreases with increasing distance from the electrodes and eventually reaches equilibrium with the room temperature of 295 K.