Loss of vibrational equilibrium between CO2 molecular levels coupled by a Fermi resonance in amplifying media

It is shown that a Fermi resonance between the 10⁰0 and 02⁰0 vibrational levels does not establish a Boltzmann distribution of these level populations under conditions typical of cw and pulsed CO₂ lasers, i.e., the condition T₁= T₂ widely used in calculations of these lasers is not satisfied.