The emission spectra are measured for different dispersion states of Pblf in NaCl crystals. A model for Pb2+ luminescent centres is proposed, which is able to bring into accord the kinetics revealed by optical and electrical methods.Les spectres d'emission pour diffkrents &ate de dispersion da Pblf dans les cristaux de NaCl ont btk mesurbs. On a propose un modhle de centre luminescent Pb2+, capable de mettre en accord la cinbtique trouvbe par les methodes optiques et Blectriques.

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The state of dispersion of Pb2+ in highly doped KCl crystals after different heat treatments is investigat,ed. Optical and X-ray diffraction measurements show that the new phase formed in KCl crystals by precipitation of the impurity is imperfectly ordered and composed of agglomerations of cation-vacancy dipoles, different from the case of Pb-doped NaCl crystals where a PbCI, phase is obtained. X-ray diffraction and luminescence data show that after both, strong precipitation and dissolution, the impurity evolves towards the same equilibrium state characterized by partial aggregation of Pba+ cation-vacancy dipoles.On a BtudiB l'btat de dispersion du Pb2+ dans les cristaux de KCI fortement impurifi6s soumis b des diffbrents traitements thermiques. Les mesures de diffraction des rayons X et les donnbes optiques ont conduit b la conclusions que la nouvelle phase obteniie par la prbcipitation du Pb est une phase peu ordonke, formBe par des associations de dipoles Pb2+-vacance, btat different de la phase de PbCI, obtenue dans le cas du cristal de NaC1:Pb. Les rbsultats radiocristallographiques et de luminescence ont indiqub qu'aprks une forte prbcipitation ou aussi bien dissolution, l'impureth bvolue vers un m4me &at d'bquilibre caractkrish par l'agglom6ration partielle des dipoles Pb2+--vacance.

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Data Concerning the Growth and Some Optical Properties of NaReo 4 , 9 e C 1 , , NH4ReO4 ZJing le CrystalsThe interesting features of rhenium and its salts stimulated the present study on the growth conditions of NaReO ReCl and NH ReO single crystals. The structure and the physical propert#&% the t t r e e combun%s advise on a method of growing from a melt ( PLOVMCK, SCHMlDT ) or on the grawth from aqueous solution ( MORROW).