We decompose the vertical electron detachment energies (VDEs) in solvated-electron clusters of alkali halides in terms of (i) an electrostatic contribution that correlates with the dipole moment (mu) of the individual alkali halide molecule and (ii) a relaxation component that is related to the polarizability (alpha) of the alkali halide molecule. Detailed numerical ab initio results for twelve species (MX)(n)(-) (M=Li,Na; X=F,Cl,Br; n=2,3) are used to construct an interpolation model that relates the clusters' VDEs to their mu and alpha values as well as a cluster size parameter r that we show is closely related to the alkali cation's ionic radius. The interpolation formula is then tested by applying it to predict the VDEs of four systems [i.e., (KF)(2)(-), (KF)(3)(-), (KCl)(2)(-), and (KCl)(3)(-)] that were not used in determining the parameters of the model. The average difference between the model's predicted VDEs and the ab initio calculated electron binding energies is less than 4% (for the twelve species studied). It is concluded that one can easily estimate the VDE of a given high-symmetry solvated electron system by employing the model put forth here if the alpha, mu and cation ionic radii are known. Alternatively, if VDEs are measured for an alkali halide cluster and the alpha and mu values are known, one can estimate the r parameter, which, in turn, determines the "size" of the cluster anion. (C) 2003 American Institute of Physics.