Stimulated thermal scattering in a gas under conditions of thermodynamic nonequilibrium

Characteristics of stimulated thermal scattering are investigated under conditions of a strong thermodynamic nonequilibrium. It is shown that a thermal instability resulting in a transient threshold-free stimulated thermal scattering is possible in media with inhomogeneously excited internal degrees of freedom or in chemically active media. The stimulated scattering gain and the scattering angle are then governed by the degree of nonequilibrium of the medium, and by the dependences of the power of the source pumping equilibrium levels and of their relaxation time on the temperature and density of the gas.