Net emission of Ar–H₂–He thermal plasmas at atmospheric pressure

The net emission coefficient (NEC) has been calculated for Ar–H 2 –He thermal plasmas and for a temperature range from 5000 to 30 000 K. The plasma is supposed to be in local thermodynamic equilibrium at atmospheric pressure. This study takes into account the radiation resulting from the atomic continuum, the molecular continuum and the atomic lines. Particular attention has been paid to the treatment of helium lines broadenings. The results of NECs are presented for pure gases and Ar–H 2 –He mixtures. Radiation is weak in pure helium at low temperatures because of the high ionization energy of this species. Conversely, at very high temperature, the influence of hydrogen tends to decrease because ionic lines do not exist for this last species. Finally, a small proportion of helium in Ar–H 2 mixtures does not change the NEC because of the weak intensity of the helium lines.