The term values of the ground and excited Rydberg states of alkali metal atoms trapped in rare gas matrixes were derived from an empirical model potential. The anal. potential smoothly connects the Coulomb potential near the core with the shielded Coulomb potential beyond the first shells of surrounding matrix atoms. The potential does not depend on the specific dopant, and is detd. for each rare gas matrix in a unique way from the polarization energy of the crystal by the ionic core P+ and from the electron affinity V0. The predicted transition energies agree with the existing exptl. data. [on SciFinder (R)]