Optical absorption of radiation-produced defects inNaMgF3andRbCaf3

Optical-absorption bands produced by electron irradiation of the compounds NaMg${\mathrm{F}}_3$ and RbCa${\mathrm{F}}_3$ were measured as a function of radiation dose, dose rate, and temperature. The band positions, growth rates, and stabilities, were compared with corresponding absorptions in alkali halides and KMg${\mathrm{F}}_3$, permitting the bands observed in NaMg${\mathrm{F}}_3$ to be attributed, respectively, to self-trapped holes, $F$-type centers, or interstitial defects. The results for RbCa${\mathrm{F}}_3$ were not as closely analogous with the behavior of alkali halides. Nevertheless the results for both compounds clearly showed that defect production by a radiolysis mechanism was taking place. Since NaMg${\mathrm{F}}_3$ is orthorhombic and RbCa${\mathrm{F}}_3$ changes from cubic to tetragonal as the temperature is lowered below 198 K, and since their radiation behavior exhibited no effect whatsoever of these structural differences, the results imply that a replacement collision along close-packed $〈110〉$ halide rows, that has long been assumed to be necessary for radiolysis, may not, in fact, be necessary for defect production.