  A low density binary mixture of granular gases is considered within the
Boltzmann kinetic theory. One component, the intruders, is taken to be dilute
with respect to the other, and thermal segregation of the two species is
described for a special exact solution to the Boltzmann equation. This solution
has a macroscopic hydrodynamic representation with a constant temperature
gradient and is referred to as the Fourier state. The thermal diffusion factor
characterizing conditions for segregation is calculated without the usual
restriction to Navier-Stokes hydrodynamics. Molecular dynamics simulations are
reported for comparison with the results for this idealized Fourier state.
