Impurity Raman Scattering from CaF2:Ce

We have investigated the scattering from Ca${\mathrm{F}}_2$:Ce crystals in which part of the trivalent Ce impurities have been reduced to the divalent state. Although the ${\mathrm{Ce}}^{2+}$ concentration was extremely low (∼ 10 ppm) we observe electronic Raman scattering. In addition, we have observed a defect-induced spectrum closely approximating the unperturbed one-phonon density of states. The latter scattering is due to phonon modulation of the impurity Rayleigh scattering.