Optical and scintillation properties of SrI2:Yb2+

The luminescence and scintillation properties of SrI2:0.5%Yb2+ have been investigated. SrI2:Yb single crystals were grown by the vertical Bridgeman method from the melt. They showed a light yield of 38,400 ph/MeV and energy resolution of 12.5% for the 662 keV full absorption peak. Yb2+ photoluminescence intensity and decay time were studied between 78 and 600 K. Two emission bands centered at 418 and 446 nm were observed and ascribed to spin-allowed and spin-forbidden Yb2+ 5d-4f transitions, respectively. Their corresponding room-temperature decay time constants are 710 ns and 77 mu s. Both, the emission intensities and the decay time constants vary with temperature. The obtained results were interpreted using a model of self-absorption of Yb2+ emission and a model of non-radiative relaxation of the electron from the low spin to the high spin 4f(13)5d Yb2+ excited states. The radiative lifetime of the low spin Yb2+ excited state was determined as 400 ns. (C) 2014 Elsevier B.V. All rights reserved.