Continuum Infrared Radiation from High-Temperature Air and Nitrogen

Abstract

The absolute intensity of infrared radiation from air and nitrogen, shock‐heated to an equilibrium temperature of 6000°—9000°K, has been measured at nearly atmospheric density over the wavelength range of 2–8 μ. This continuum radiation is interpreted as due to free—free scattering of electrons from neutral atoms and molecules. The temperature dependence of this radiation has been determined at 2.35 and 3.88 μ for air and at 3.07 μ for nitrogen. An analysis of the temperature‐dependent data, using the classical Kramers' relation, has resulted in establishing the effective Coulombic charges, Z, for N₂, N, and O, which indicate that in air the bulk of the free—free radiation is due to scattering from nitrogen atoms and molecules; oxygen gives a negligible contribution. A small change in slope of the wavelength data for air occurs around 3.6–4.0 μ. Speculation concerning the origin of this radiation is presented.