Relaxation of Quantum State Population and Volume Viscosity in He/H-2 Mixtures

A kinetic model for He-H-2 mixtures is studied in a regime where elastic collisions are fast and inelastic collisions are slow. Application of the Chapman-Enskog method yields a state to state fluid model where each quantum state is a separate pseudo species. The relaxation of quantum state population towards thermodynamic equilibrium is investigated as well as the definition of volume viscosity coefficients. The theoretical results are applied to the quantum state population and volume viscosity of molecular hydrogen on the basis of a complete set of cross sections for the He+H-2 (v, j) system.