Exchange enhancement ofCo2+andMn2+transitions due to radiation defects

A study of the radiation-induced impurity optical transitions in KMg${\mathrm{F}}_3$ crystals has been made. It is found that the enhanced oscillator strength of the defect centers is predominately due to exchange. The data indicate that most of the transitions are due to perturbed ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Co}}^{2+}$ transitions. Investigation of the effects of radiation temperature, optical bleaching, and annealing on the optical properties of KMg${\mathrm{F}}_3$: ${\mathrm{Mn}}^{2+}$ indicates that two types of defects are involved. One is a $F$-center-${\mathrm{Mn}}^{2+}$ defect and the other is tentatively identified as an interstitial-$F$-center-${\mathrm{Mn}}^{2+}$ defect.