Spectroscopic investigation of atmospheric pressure cold plasma jet produced in dielectric barrier discharge

Non-thermal cold atmospheric pressure plasma jet (APPJ) produced in multi-pulse dielectric barrier discharge (DBD) preferentially heats the electrons that subsequently transfer their energy to the other plasma species converting them into reactive species. Therefore the characterization of different energy groups of electrons is essential for efficient production and control of reactive plasma species contributing to surface modifications. Here we present the spectroscopic investigations of the APPJ produced in multi-pulse DBD using pin electrode configuration. Boltzmann plot relates the emission intensities of the several Ar-I spectral lines to their corresponding threshold excitation energies to give the electron temperature more precisely. The Stark broadening of the Ar-I (696.54 nm) line profile gives the electron number density after de-convoluting the contributions of the Doppler and instrumental broadenings. Plasma measurements correlate the gas flow rate, applied jet power across the electrodes, and a group of electrons contributing to optical emission. Sequential imaging correlates the size of the plasma bullets momentarily with the discharge pulse for different argon flow rates and applied jet powers. With an increasing flow rate of up to 1.4 L/min, the plasma plume of the jet becomes more elongated, intense, and spatially uniform. However, the glow intensity and size of the plume start reducing with a further increase in gas flow rate. Experimental findings propose plasma processing for small-scale localized plasma surface treatments.