Relaxation in a Dilute Binary Gas Mixture

Abstract

The relaxation of a dilute hard‐sphere binary gas mixture is studied in the limit of vanishingly small concentration of one of the species. The velocity autocorrelation function and diffusion coefficient are evaluated by the integral approximation and Chapman–Enskog methods. Solutions are obtained as a function of the ratio of the masses of the two species and the limiting cases of the Rayleigh and Lorentz gases are considered in some detail. While the convergence of the Chapman–Enskog method becomes poor as the Lorentz limit is approached, the integral approximation yields solutions which are exact in this limit. In the Rayleigh limit both methods yield the exact result.