What mechanisms can explain the origin of the continuous emission spectrum of a hot gas?

Various mechanisms of the appearance of radiation with a continuous spectrum in a discharged hot gas are possible. The first of these is the recombination of free electrons with positive ions. The energy of free electrons is not quantized; therefore, the resulting spectrum is limited only from the side of low frequencies. The second mechanism is bremsstrahlung of free electrons moving in electric fields created by positive plasma ions. Since the spectrum of velocities of free electrons in plasma is continuous and they pass at different distances from positive ions, the spectrum of their bremsstrahlung is also continuous. The third mechanism is radiation during the formation of negative ions. A free electron can have any energy prior to joining a neutral atom. Therefore, when electrons combine with neutral atoms, radiation with a continuous spectrum appears.