New perturbed Pb−-aggregate centers in electrolytically colored KBr:Pb2++(Ca, Ba) crystals

New luminescent centers with a large near-infrared emissions were obtained by unusual electrolytic coloration method (low temperature and high electric field) in the KBr:Pb2+ crystals co-doped with alkali-earth ions (Ca2+, Sr2+, Ba2+). These so-called Tx centers involve Pb−-negative metal ions and the presence of at least one alkali-earth ion, which enhances the photoluminescence properties of those centers. The formation of these new centers is due to the presence of F-centers created in the process of electrolytical coloration. The photoluminescence properties, together with the magnetic circular dichroism spectra, prove the existence of at least one paramagnetic luminescent center.