Kinetic model analysis of time-dependent problems in polyatomic gases

In this work we analyze time-dependent problems like sound propagation and light scattering in dilute polyatomic gases by using a kinetic model of the Boltzmann equation that replaces the collision operator by a single relaxation-time term which is compatible with Grad's 6-moment approximation. Comparison of the theoretical results with available experimental data in nitrogen, oxygen, carbon dioxide and methane shows that the model equation can be used to describe the acoustic properties and the light scattering spectrum of polyatomic gases in both hydrodynamic and kinetic regimes as long as the external oscillation frequency is smaller than the frequency required for the translational and the internal degrees of freedom to come to thermal equilibrium.