  Starting from a set of coupled Boltzmann equations, we investigate the
thermalization of a two-species cold atomic gas confined either in a box or in
an isotropic harmonic trap. We show that the thermalization times, by contrast
to the collision rate, depend on the interferences between scattering partial
waves. The dynamics of thermalization in a harmonic trap is also strongly
dependent upon the ratio between the collision rate and the trap frequencies.
