OPTICAL-PROPERTIES OF AG+ IMPURITIES IN KMGF3 CRYSTALS

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