Calculation of temperature and population distribution in DF laser cavity based on emission spectrum

The relational expressions between gain coefficient, intensity of spectral lines and the temperature, population distribution in optical cavity were established, and the emission spectrum of a combustion-driven DF chemical laser was measured, calculation based on spectral data showed that the temperature in optical cavity was 381.4 K, the ratio of population in ν=1 vibration level to ν=0 level, population in ν=2 level to ν=1 level, and population in ν=3 level to ν=2 level were 0.60～0.62, 0.676 4, 0.71～0.74, respectively.