Effect of the addition of non-ionic surfactants on the emission characteristic of direct current atmospheric pressure glow discharge generated in contact with a flowing liquid cathode

A direct current atmospheric pressure glow discharge generated in contact with a flowing liquid cathode was used to study the effect of the concentration of two non-ionic surfactants, i.e., Triton x-45 and Triton x-405 added to electrolyte solutions, on the emission characteristic of the excitation source by using optical emission spectrometry. The emission intensity of different molecular and atomic species as well as the background level were measured. Selected spectroscopic parameters, i.e., rotational temperatures of OH and N-2 molecules, excitation temperatures of Co and H atoms, the electron number density and the intensity ratio for Mg II to Mg I lines, were also determined. The net intensity of atomic emission lines of several metals (Cs, Cu, Hg, Mg, Mn and Pb) was found to be enhanced by more than 4 times in the presence of the heavier surfactant in solution at the concentration corresponding to 5 times its critical micelle concentration. Coincidently, the intensity of the background in the vicinity of these lines and its fluctuation were also significantly decreased. Possible changes in sputtering, collisional-recombination and excitation processes that may occur in the near-cathode zone of the discharge are discussed and the phenomenon explained.