  We consider a model of a scalar field, with dispersion relation {\omega}(k),
coupled to a random medium of two level atoms. We investigate the dynamics of
states with at most one quanta of excitation in the system. In a high frequency
limit, the probability amplitudes are shown to satisfy kinetic equations. Under
additional hypotheses on the dispersion relation, we obtain an analytically
solvable expression in the diffusion limit.
