Luminescence and EPR of uranium-activated sodium fluoride

EPR and luminescence measurements on uranium-activated sodium fluoride are reported. Six types of U5+ EPR centres, obtained in these crystals after x or gamma irradiation, having tetragonal, rhombic or monoclinic symmetry are discussed. Tentative charge compensation mechanisms are proposed. The connection with parent U6+ luminescent centres is also discussed. It is proved that for the main luminescent centre obtained in oxidising conditions (5636 AA line) hexavalent uranium has five oxygens and one fluorine as near neighbours.