Sum rules forFcenters in alkali halides

The purpose of the present paper is the application of sum rules to the study of the unperturbed $F$-center ground state in three alkali halides (KBr, KCl, and RbCl). The comparison between theoretical expressions for the moments of the absorption spectrum and their numerical values computed from the experimental spectra, gives the mean radius, the mean kinetic energy, and the mean charge density seen by the electron. These parameters allow a determination of the shape of the electron charge density, which is found to be in good agreement with electron-nuclear-double-resonance measurements.