RADIATIVE TRANSFER IN OXYGEN, NITROGEN AND AIR THERMAL PLASMAS BETWEEN 300 AND 30 000 K

We have calculated the mean absorption coefficients of pure nitrogen and oxygen in the assumption of a grey body on six frequency intervals. This calculation takes into account the radiation due to the atomic continuum, the molecular continuum, the molecular bands (several systems for O₂, N₂, NO and N₂^*) and the atomic lines. A special treatment of the resonance lines has been performed in order to take into account the self-absorption of these lines. Then, a 1D calculation of the radiative transfer has been performed and has shown that nitrogen is more emissive than oxygen in the temperature range between 8 000 and 15 000 K, whereas the absorption by molecular oxygen is higher than that of nitrogen when T < 4000 K. This last phenomena is mainly due to the photodissociation mechanism.