Electron density and temperature measurement by continuum radiation emitted from weakly ionized atmospheric pressure plasmas

The electron-atom neutral bremsstrahlung continuum radiation emitted from weakly ionized plasmas is investigated for electron density and temperature diagnostics. The continuum spectrum in 450-1000 nm emitted from the argon atmospheric pressure plasma is found to be in excellent agreement with the neutral bremsstrahlung formula with the electron-atom momentum transfer cross-section given by Popović. In 280-450 nm, however, a large discrepancy between the measured and the neutral bremsstrahlung emissivities is observed. We find that without accounting for the radiative H₂ dissociation continuum, the temperature, and density measurements would be largely wrong, so that it should be taken into account for accurate measurement.