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Phase-resolved optical emission spectroscopy of a transient plasma created by a low-pressure dielectric barrier discharge jet

A transient plasma created by a low-pressure dielectric-barrier discharge operated with argon was investigated by means of optical emission spectroscopy and imaging. Images of the discharge and emission spectra were recorded with sub-phase resolution and relative densities of excited argon states were obtained. Profiles of densities and electron temperatures were evaluated for the discharge cycle by comparison with results of a collisional-radiative model (CRM). To overcome difficulties in sub-cycle modelling of the important argon 1s states, a combination of the CRM with a density estimation based on radiation-trapping is proposed. Absolute densities of all four 1s states were measured and additionally verified by tunable laser absorption spectroscopy. The presented combination may help to improve optical diagnostics of rare gas plasmas in cases were the dominating processes for the 1s states are not known with sufficient accuracy.