Optical centers related to silver in Ag+-doped strontium fluoride crystals

The spectroscopic properties of several Ag+ activated strontium fluoride crystals-originating from different batches-were examined. Absorption, emission and excitation experiments including luminescence dynamics and polarization studies were performed at various temperatures. Four Ag+ related photoluminescent centers were found. Their properties are described. The predominant species in the as-grown crystals emits in the UV (at 315 nm) and was shown to be the single Ag+ ion in cubic surroundings. Two other centers emitting in the violet (400 nm) and in the yellow (550 nm), respectively, were attributed to (Ag+)(2) pairs with different geometries. Models of these pseudo-molecular clusters are proposed. The nature of the system which produces a weak green (500 nn) luminescence remains open to questions.