Nonlinear vibrational relaxation in a molecular gas

It is shown that VT relaxation in a diatomic gas has a nonlinear character due to VT transition in each of the colliding molecules. It is also shown that a quasi-steady (nonequilibrium) state cannot be attained in the relaxation process of anharmonic molecules. In the nonlinear theory of VT exchange examined here, the relaxation of the vibrational energy of harmonic oscillators is a function of time, not a constant as is the case in the linear approximation.