A semi-continuous extended kinetic model

A set of semi-continuous model Boltzmann equations governing the evolution of a three-component gas mixture is presented. The third species is treated as an excited state of the second species. The model takes into account collisional excitation and de-excitation processes as well as the interaction with. monochromatic photons. A kinetic equation for photons is coupled with the model Boltzmann equations. Conservation properties are established and an H-theorem is proven. Numerical solutions to simple test cases are provided.