Study on obtaining rotation temperature by using the relative intensity of the CN spectrum in the ultraviolet band

The non-equilibrium ultraviolet radiation characteristics of plume and shock are closely related to flight parameters such as vibration-rotation temperature, where temperature is the most important thermodynamic quantity for calculating non-equilibrium radiation. CN is the main product of aircraft reentry into the atmosphere and the ablation of carbon-based composite materials, and has very high emission efficiency, making it one of the best molecules for high-temperature gas temperature measurement. In this paper, the two-temperature model and the line-by-line method are used to calculate the CN ultraviolet spectral radiance, and the spectral structure of the violet band is analyzed. The effects of vibration temperature and rotation temperature on the spectral intensity and spectral shape of ultraviolet radiation under thermodynamic non-equilibrium conditions are discussed. According to the relationship between the band tail of CN violet band v=0 peak and the vibration temperature and rotation temperature, a method to invert the rotation temperature using the the slope of CN spectral relative intensity