The atmospheric-pressure plasma needle is a promising source that can be used efficiently for different industrial applications. A radio frequency (RF) (13.56 MHz) generator was used to generate a He-O 2 /Ar mixture plasma. The ground-state oxygen atomic density [O] was calculated as a function of discharge parameters by "actinometry". The Ar-I (2p 1 → 1s 2 ) line at 750 nm and the O-I ( 3 P → 3 S) line at 844 nm were used to estimate the [O] atomic density. The rotational temperature T R of He-O 2 /Ar mixture was measured from the rotational levels of the "first negative system" (FNS) N + 2 (B 2 Σ + u , ′ → X 2 Σ + g , ′′ ) by using the "Boltzmann plot". The effect of discharge parameters on the atomic oxygen density [O] and the gas temperature was monitored. These results show that [O] density increases with RF power and O 2 concentration, but decreases with the gas flow rate. Whereas the gas temperature increases with increase in the input RF power, it decreases with increase in the gas flow rate and O 2 concentration in the mixture. Since the [O] atomic density contributes to plasma-based biomedical applications, the proposed optimum conditions for plasma-based decontamination of heat-sensitive materials in the present study are 0.6% oxygen, 500 sccm flow rate, and 26 W RF power.

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