Measurement of Metastable Atom Populations Along an Argon Plasma Column Generated at Atmospheric Pressure

This paper describes a procedure for experimental determination of metastable and resonant populations along a surface wave argon plasma column at atmospheric pressure. As modeling work progresses extensively, an experimental database is necessary to confirm these models. Obtained results, within the range of values reported in literature, indicate that densities of metastable and resonant levels grow along the plasma column for positions near the energy coupler device, where the energy of the surface wave which creates discharge is the highest. This behavior is also found for electron density and temperature; however, it is not the same for gradient. Therefore, at atmospheric pressure, populations of 4s levels are not only controlled by collision with electrons from ground state, but the dissociative recombination mechanism is also important, in agreement with results found by other authors using collisional-radiative models.