This work provides an insight into the generation of excited nitrogen species by allowing noble gases to interact both with one another and ambient air. He and Ar were utilized to generate the optimum selectivity process to create reactive nitrogen species. An optimum setting for the generation of excited molecular nitrogen species, based on their excited energy levels, was obtained when using a mixture of Ar-He at a ratio of 10:1. At that point, when a voltage of 27 kV is applied to the system, it reached the maximum efficiency for selectivity processes to occur which allowed for a greater non-radiative transfer of energy through the mixture of noble gas atoms and into the molecular nitrogen present in ambient air. K E Y W O R D SAC barrier discharges, kinetics, nitrogen, non-thermal plasma, optical emission spectroscopy (OES)

The paper deals with monitoring the plasma chemistry of an atmospheric plasma low-frequency AC power supply. The study is based on optical spectroscopy and electrical measurements as diagnostic methods. The work includes details of developing and operating an in-house made, non-thermal, dielectric-free atmospheric plasma system, built for biological and agriculture applications. The experimental results clearly show the cross-dependence of the measured outputs (O3, O2, N2) and a wide range of process parameters (duty cycle, discharge frequency, voltage, etc.). A design-of-experiment approach is taken for phase-resolved optical emission spectroscopy of oxygen and nitrogen spectral lines/bands. The new plasma system allows an increase in the plasma-surface interaction selectivity and reduces plasma-induced damages to the surface.

The new generation of atmospheric plasma system, which is running in the pulse resonance cycle, is designed to increase the possibility of applications for an atmospheric plasma treatment. This plasma system, together with a specially designed plasma pin reactor, is able to generate plasma discharge at an area of hundreds of cm 2 with the air gap between electrodes of up to 65 mm.