Model of Nonequilibrium Emissivity of Diatomic Molecules Averaged over the Rotational Structure

The article presents the derivation of the calculated relations for the model of the emissivity of the electronic vibrational bands of diatomic molecules averaged over the rotational structure. The model is based on the ab-initio expression for the integral radiation emission coefficient of the rotational line of an electron-vibrational-rotational quantum transition and the results of ab-initio calculations of the Einstein coefficients of rovibronic quantum transitions of spontaneous emission. Calculation formulas are obtained for the averaged emissivity coefficients of heteronuclear molecules. Their validity is shown for homonuclear molecules, including states of different symmetries, in the spectra of which alternating intensities of the emission of rotational lines are observed. Using the obtained relations, spectra of nonequilibrium radiation from the shock wave relaxation zone were obtained in shock wave experiments in air at a speed of 7.3 km/s and a pressure of 0.7 Torr in a low-pressure chamber. The results were compared to experimental data.