Back reactions in color-center production: A study of a di-interstitial center in Li-doped KBr

The production of $V\left(306\right)\mathrm{}$ centers, constituted by two interstitial halogen atoms trapped at a lithium impurity, is studied in doped KBr in the 190-300°K temperature range. Above 210°K the $V\left(306\right)\mathrm{}$-center production saturates and the saturation concentration decreases with increasing temperature. The saturation of the $V\left(306\right)\mathrm{}$-center production is correlated to a first stage in the $F$ center growth curve. Some evidence for a mechanism of saturation of the $V\left(306\right)\mathrm{}$-center production based on the mobility of anion vacancies is given.