Rotational nonequilibrium and line-selected operation in CW DF chemical lasers

A numerical analysis of rotational nonequilibrium effects in CW DF chemical lasers is presented. The rotational master equations incorporate the effects of simultaneous mixing, chemical pumping, rotational cross relaxation, and radiative emission. Rotational cross relaxation is described by "exponential gap" models in which ΔJ is unrestricted. Results of this analysis indicate that rotational equilibrium can be a poor assumption for high J levels even under small-signal conditions. The model predictions are in good qualitative agreement with observed multiline resonator spectra. Performance loss due to rotational nonequilibrium is predicted to be modest (∼15 percent) for multiline operation, with larger losses predicted for line-selected modes. Criteria for efficient line-selected operation are presented.