In the frame of extended kinetic theory, a Lorentz-type model is propo
sed, which allows for inelastic scattering between a swarm of test par
ticles and a background of heavy field particles. For the sake of simp
licity, only two internal energy levels are considered for the backgro
und molecules. After analysing the main properties of the collision op
erator (null space and relaxation to equilibrium), the diffusive appro
ximation is recovered as the asymptotic limit when the mean free path
tends to zero, and an analytical solution in implicit form is derived
for the space homogeneous problem.