Optical absorption by rare-gas atoms in alkali-metal rare-gas alloys

We present results of a Cluster-Bethe Lattice Method calculation of the optical absorption due to rare-gasses in alkali-metal rare-gas alloys. A specific application to the Cs-Xe alloy reveals that the main features of the absorption for the whole concentration range can be understood in terms of a single-quasiparticle model. The effects of short-range order are investigated.