Optical properties of Ag+ impurities in KMgF3 crystals

The optical properties of Ag+ impurities in single crystals of the perovskite-like KMgF3 are studied. The optical absorption spectra consist of two bands at 192 and 213 nm, which are attributed to parity-forbidden 4d(10) --> 4d(9)5s transitions by analogy with the alkali halides. Under optical excitation in each of the absorptions, only one photoluminescence band is observed at 243 nm, which is thermally enhanced. The temperature dependence of its decay time is similar to that found for alkali halides, and therefore its behaviour is analogously attributed to two emitting levels, the lowest one being metastable. Measurements of the thermally stimulated luminescence, and of its spectral distribution show that for KMgF3:Ag+ two kinds of emission mechanism coexist, one due to the deexcitation of Ag+ ions, and the second caused by intrinsic deexcitation of the host lattice. The features of the optical behaviour of Ag+ in KMgF3 crystals are compared with those known of for Ag+ in other systems