Stability of Stationary States for Molecular Gases under Velocity-Selective Excitation
During more than a decade, kinetic phenomena arising in gases under velocity-selective excitation have been the object of many studies (see, in particular, Refs. [1–6]). When the momentum relaxation rates v e for the excited and v g for the ground-state molecules are different, the macroscopic state of the gas entirely changes. Recently, the possibility of the existence of non-stationary regimes and the oscillatory dynamics in these conditions has been discussed [7,8]. These studies make the problem of the stability of the stationary solutions obtained under velocity-selective excitation quite important. This problem has been partially resolved  for a single-component resonant gas in the case when the rate of spontaneous relaxation γ is much higher than the frequency v of velocity-changing collisions, γ ≫ v. However, for the case γ ≤ v, the problem remained unsolved. Meanwhile, the latter situation is most typical for molecular vibrotational transitions where many of the experiments on the velocity-selective excitation are being done. The main purpose of the present work is to derive a criterion of stability for a mixture of a resonant molecular gas and a buffer gas using a simpler collision model, with a possible generalization to the case γ ≤ v.
KeywordsOscillatory Dynamic Optic Comm Macroscopic State Specular Surface External Force Field
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