Ar metastable densities (3P2) in the effluent of a filamentary atmospheric pressure plasma jet with humidified feed gas

Abstract

The Ar(3P2) metastable density in the effluent of the cold atmospheric pressure plasma jet kINPen was investigated as a function of the feed gas humidity, the gas curtain composition, and the distance from the nozzle by means of laser atomic absorption spectroscopy. The filamentary character of the plasma jet was considered as the absorption signals are from single individual events. From the effective lifetime, the quenching coefficient for Ar(3P2) by water was determined. A maximum Ar(3P2) density of (6.0±0.7)×1013 cm−3 was obtained close to the nozzle for a feed gas humidity of 20 ppm. The densities near the nozzle decreased inversely proportional to the water content in the feed gas leveling off at approximately 1×1013 cm−3, independently from the gas curtain composition. With the addition of water to the feed gas, the excitation dynamics changed, and the production and lifetime of Ar(3P2) was reduced. The impact of Ar(3P2) on the reactive species composition in the effluent was found to be smaller than within the plasma zone inside the plasma jet device.

Effect of Plasma On-Time with a Fixed Duty Ratio on Reactive Species in Plasma-Treated Medium and Its Significance in Biological Applications

“…It is now well known that the ROS/RNS played an important role in the biomedical application of NTAPP [ 12 , 13 , 14 , 15 , 16 , 17 ]. Variable anti-tumor efficacy results from differences in the composition and quantity of plasma-generated ROS/RNS between devices and from feed gas admixtures [ 18 , 19 ]. The NTAPP is well known for producing enormously high ROS/RNS levels.…”

Measurement and reduction of Ar metastable densities by nitrogen admixing in electron beam-generated plasmas

“…The Ar metastable levels are typically used for LIF measurements of neutral velocity distribution functions [34][35][36][37][38]. The density of Ar metastables is most frequently studied by optical absorption [39][40][41][42] and emission [43] techniques. In addition, Nikolicé t al [44] have demonstrated a density measurement of Ar metastable and resonant levels in a microwave plasma, by combining LIF, OES of excited Ar levels, and kinetic modeling of the Ar I level population.…”

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