Translational nonequilibrium in a free jet expansion of a binary mixture

Frozen parallel temperatures and frozen velocities of each species in the free jet expansions of helium-argon, helium-neon and neon-argon gas mixtures have been measured by a molecular beam time-of-flight method in the range of P0d=1-2 Torr.cm, where P0 is the source pressure and d the orifice diameter. We have obtained that the frozen temperature of the heavy species is higher than that of the light species and that the ratio of the frozen temperature of the heavy species to that of the light species increases with increasing their mass ratio. We have also made the numerical calculation for the source flow expansion of the binary mixture using an ellipsoidal velocity distribution function. The calculations have been made for a rather larger value of P0d compared with the present experiments, but the results are qualitatively in good agreement with the present experiments in the dependency of the frozen temperature of each species on the mole fraction of the heavy species and on the mass ratio