OES diagnostics of atmospheric pressure argon plasma: Electron temperature and density assessment through visible bremsstrahlung inversion method and collisional-radiative model.

This article focuses on diagnosing electron temperature and density in atmospheric pressure argon plasma by combining continuum and line spectral analyses using optical emission spectroscopy (OES). The study employs visible bremsstrahlung inversion (VBI) to derive a partial electron energy probability function (EEPF) from the continuum spectrum and fits a collisional-radiative (CR) model to the line spectrum using this EEPF, rather than assuming a conventional Druyvesteynian EEPF. Results show that electron densities obtained with the arbitrary EEPF are about an order of magnitude lower than those from the Druyvesteynian assumption but align well with a two-temperature distribution model, improving accuracy in plasma diagnostics. The method also highlights the importance of constraining the gas temperature to avoid overfitting and suggests that this combined spectral approach offers a more reliable alternative for characterizing nonequilibrium argon plasmas at atmospheric pressure.