A luminescence and absorption spectroscopy study of KH 2PO 4 crystals doped with Tl + ions

Abstract

We report experimental study on luminescence and optical properties of single crystals KH 2PO 4 (KDP) doped with Tl + ions (KDP:Tl) carried out at 10-480 K. The 4.5 eV photoluminescence (PL) of KDP:Tl originates from radiative electronic transitions 3P 1 → 1S 0 in the Tl + ions upon excitation by UV-photons, X-rays, and electron beam. This luminescence can be induced by direct photoexcitation, or through the recombination process with participation of the lattice defects located in the vicinity of Tl + ion. These excitation mechanisms lead to different temperature behavior of the luminescence intensity. The PL excitation spectra of KDP crystals containing a small amount of the Tl + ions (0.001-0.008 wt.%) comprises peaks at 5.7-5.8, 6.9, and 7.3-7.4 eV, corresponding subsequently to the A-, B- and C-optical transitions in Tl +. The PL time response has single-exponential behavior with an average lifetime of τ = 280 ± 8 ns. Under exposure to ionizing radiation (X-rays, or electron beam) the intensity of the Tl + luminescence increases depending on the exposure time. The origin of this phenomenon was associated with creation of defects in the hydrogen sublattice of KDP. © 2012 Elsevier B.V. All rights reserved.