Level degeneracy in the operation of a Zeeman ionic laser

The Coulomb broadening of a magneto-optical resonance of degenerate two-level ions in the field of a standing wave is calculated. Under the conditions of linear polarisation of this wave, of the normal Zeeman effect, and of weak saturation, the broadening is described by familiar expressions for multistage and two-photon resonances in separate three-level subsystems and the coefficients in these expressions depend on the angular momenta. The profile of a nonlinear resonance in the dependence of the output power of a single-frequency Zeeman ionic laser on the applied magnetic field consists of a narrow central interference peak, a wide diffusion part, and Lorentzian wings. It is shown that, in the case of a broad lower active level, the J → J+1 transitions are more favourable for the observation of a two-photon resonance and the relative amplitude of the resonance is not less than 2/7.