闪烁晶体的发光研究进展

概述了近年来闪烁体发光研究的进展,主要介绍用于未来高能物理实验的新型闪烁体发光机理研究,选取我们在研BaF₂,BaF₂:RE,CeF₃以及PbWO₄中的一些新进展。重点谈及三点:(1)在BaF₂的“价带^→芯带”跃迁发光研究基础上进行稀土(Gd³⁺-Eu³⁺)掺杂时观察到的量子剪裁以及对多光子发光的新思考;(2)CeF₃晶体发光的级联能量传递中,Ce³⁺(290nm发射带)与缺陷发光中心(340nm发射带)间能量传递及其传递效率的温度依赖;(3)PbWO₄晶体的发光中心研究中,提出以“WO₄^-2+O_i”绿光中心替代“WO³+F”中心观点的依据。同时也简介了医用闪烁体的最新进展。

Luminescence of Scintillation Crystals

Progress in the scintillator luminescence research is summarized in this paper.The summary is concentrated on luminescence mechanism of the scintillators used for high energy physics in near future.New scintillators we have studied include BaF₂,BaF₂:RE,CeF₃,PbWO₄ crystals.Some new results on their luminescence mechanism were presented as follows: (1)Quantum cutting effect in Gd³⁺ and Eu³⁺ doped BaF₂ powder has been observed,and its double photon emitting efficiency was about 190%.Based on BaF₂ luminescence from "valence band → core band" transition,possible multi photon emitting from RE³⁺ in this kind of fluoride system has also been considered.(2)Temperature dependence of energy transfer from Ce³⁺ (emitting 290nm band) to defect luminescence centers (emitting 340nm band) in the CeF₃ crystals was studied at 61nm (VUV) excitation.The energy transfer was confirmed by the excitation spectra of 290nm,240nm emissions and luminescence decay curves for 340nm emission at different temperatures.At 5K,the excitation spectra of 340nm emission were quite different from that of 290nm emission,but they were almost the same shapes at 350K.Under 61nm excitation,the decay time of 340nm luminescence was postponed from about 20ns to 40ns with rising temperature from 5K to 350K.The energy transfer efficiency was rapidly increased with rising temperature from 5K to 350K.(3)The "WO₄^2-+O_i" defect as green emission center in PbWO₄ crystals was proposed and instead of "WO₃+F" center.The evidences of the view point about the "WO₄^2-+O_i" green centers were offered by the emission spectra and EXAFS data for O₂ or air annealing PbWO₄ as well as the results of theoretical calculation of electron states for the "WO₃+F" and "WO₄^2-+O_i" centers.