Use of dimer potentials to calculate the energy levels of alkali atoms in rare-gas matrices

A simple procedure is described for calculating the energy levels of an alkali atom perturbed by rare-gas neighbors in a solid rare-gas matrix, using alkali-rare-gas dimer potentials available in the literature. Straightforward analysis leads to an expression for the perturbation due to an arbitrary number of rare-gas neighbors in terms of alkali-rare-gas dimer potentials. The results of calculations for Na trapped in Ar are presented and compared with experiment and with earlier pseudopotential calculations.