Irradiation Damage in SrF2and BaF2

The thermoluminescence of rare-earth-doped Sr${\mathrm{F}}_2$ and Ba${\mathrm{F}}_2$ irradiated with x rays at 77°K is interpreted in terms of the appearance and disappearance of three paramagnetic hole centers. The $V_K$ center is similar to one previously reported in Ca${\mathrm{F}}_2$. The ${V_K}^{\prime }$ center appears to be a $V_K$ center trapped near a monovalent impurity ion. The third center, designated as $V_H$, is associated with an interstitial fluorine. Separate thermal activation of translational and rotational motion has been observed for the $V_K$ center in Ba${\mathrm{F}}_2$.