Acoustic wave amplification in a plasma of a molecular gaseous discharge

From the experimental investigation of sound propagation in a gaseous discharge, it is established that, in a stationary diffusive discharge in nitrogen, sound amplification takes place according to the linear theory, whereas a sharp transverse constriction of the discharge leads to a sharp, jump-like increase in the amplification factor because of the steep dependence of the relaxation constant of a vibrationally excited molecule on the gas temperature. This result agrees well with the nonlinear theory of sound amplification in a nonequilibrium molecular gas. It is shown that the introduction of oxygen in the nitrogen discharge leads to an increase in the sound amplification factor in the plasma, because the constant of the vibrational relaxation of an excited nitrogen molecule by oxygen is two orders of magnitude greater than the constant of relaxation of nitrogen by nitrogen.