Perculiarities of yellow luminescence decay kinetics in LiF-UO-=SUB=-2-=/SUB=- crystals

Abstract

A fast component, on the order 387 ns (300 K), has been detected in the decay kinetics of the yellow luminescence (563 nm) in LiF-UO2 crystals. It is shown that the emitting centers are anisotropic formations oriented in the crystal lattice along the second-order symmetry axes (C2) using the method of azimuthal dependence of the luminescence polarization. A model of the radiating centre is proposed and the position of the oxygen defect excited level is determined, from which the transition of an electron to the conduction band occurs. The luminescence (387 ns) from of the U5+ ion is observed as a result of electron transfer from oxygen ion to the excited U6+ level. The subsequent hole localization on U5+ in the ground state is accompanied by the reduction of the U6+ ion, that luminescence is observed in the green region of the spectrum (523 nm) with time decay 100 microsecond. Keyword: decay kinetics of luminescence, polarization, LiF-UO2 crystals.