SPECTROSCOPY OF COMPLEX DEFECTS IN CRYSTALS OF KMGF3TL+

Characterization of complex defects, formed by ionizing radiations in single crystals of KMgF3:Tl+, is carried out by means of optical spectroscopy and thermoluminescence experiments. Aggregate defects, formed by association of color centers with Tl+ impurity ions, are found to be responsible for new absorption bands in the 240-260 nm and 280-340 nm regions. Photoluminescence is obtained at 293 nm under excitation in the former and at 435 nm under excitation in the latter. Studies on the dependencies of emission spectra on dopant concentration, irradiation dose and temperature allow for the identification of two different kinds of complex centers and for the discovery of an energy transfer processes occurring between them. Spectrally resolved thermoluminescence confirms the coexistence in the samples of aggregate centers involving the Tl+ impurity ions with intrinsic defects induced by irradiation in the host crystal lattice, shows evidence of a complex emission dynamics and gives further support to the attribution of a luminescence at 240 nm to an intrinsic emission caused by excitation in the fundamental absorption of KMgF3.