Estimation of High Temperature in Air Arc by Integrated Measurement of Emission Coefficients in Concentrated Band Spectrum Radiated from N2+ Molecules

A new spectroscopic method is proposed for measuring high temperature in air arc discharges. The remarkable feature of this method is to measure the integrated emission coefficients of the selected nineteen rotational lines concentrated around the band head of 391.5 nm, which are radiated due to B²∑⁺ᵤ-X²∑⁺
_g
(0, 0) transition in N⁺₂ molecules. Since the band spectrum is not resolved into an individual line in this method, it is permissible in experiments to use a conventional mono-chromater with a low resolving power. The observed intensity is strong enough to be detected. The temperature dependence of the integrated emission coefficients has a maximum of 8900 K in air at 1 atm, and, therefore, the temperature can be easily estimated from the relative intensity measurement by means of Larenz method. The obtained temperature distributions in the wall-stabilized air arc columns are in good agreements with the theoretically obtained ones.