6d5f configuration of U4+ doped into LiYF4 crystal

Observation of luminescence due to 6d5f-->5f(2) electronic interconfigurational transitions in U4+ doped into LiYF4 crystal is reported. This luminescence originating from the lowest level of the 6d5f electronic configuration and terminating on different levels of the 5f(2) electronic configuration of U4+ consists of four relatively wide emission bands in the UV spectral range (240-370 nm), characterised by a luminescence decay time of 15 ns at 300 K. Excitation Spectrum of U4+ 6d5f-->5f(2) luminescence has a threshold at similar to250 nm and at least nine bands in the transparency region of the host. The properties of U(4+)6d5f-->5f(2) luminescence are similar to those of 5d4f-->4f(2) luminescence of Pr3+ ion embedded into crystals where the lowest 5d4f level of Pr3+ lies below the S-1(0) (4f(2)) level. U4+-doped fluoride crystals can be considered as promising materials for tuneable UV solid-state lasers based on d<---->f transitions. (C) 2002 Elsevier Science B.V. All rights reserved.