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The electronic structures for three types of PbW04 (PWO) crystals, the perfect PWO, the PWO containing lead vacancy (PWO-Vpb) and fluorine doped PWO crystal (F^-:PWO), are systematically studied within the framework of density functional theory. The computational results show that the Pb 6s state situates below the valence band so that Pb^2 ions are unable to trap holes forming Pb^3 or Pb^4 to compensate for VPb^2-. The hole-trappers in PWO-Vpb are O^2- ions. Two of the longer-bond O^2- ions share a hole forming O2^3-, and four of the longer-bond oxygen ions trap two holes forming an associated color centre [O2^3--Vpb-O2^3-], which may be the origin of the 42Onto absorption band. It is also concluded that the doping of F^- would reduce the band gap and F^- ions substituting for O^2- can effectively restrict the formation of [O2^3--Vpb-O2^3-] and weaken the 42Onm absorption band and hence enhance the scintillation property of PWO. 相似文献
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The possible defect models of Y^3+:PbWO4 crystals are discussed by defect chemistry and the most possible substituting positions of the impurity Y^3+ ions are studied by using the general utility lattice program (GULP). The calculated results indicate that in the lightly doped Y^3+ :PWO crystal, the main compensating mechanism is [2Ypb^+ + VPb^2-], and in the heavily doped Y^3+ :PWO crystal, it will bring interstitial oxygen ions to compensate the positive electricity caused by YPb^+, forming defect clusters of [2Ypb^+ +Oi^2-] in the crystal. The electronic structures of Y3+ :PWO with different defect models are calculated using the DV-Xα method. It can be concluded from the electronic structures that, for lightly doped cases, the energy gap of the crystal would be broadened and the 420nm absorption band will be restricted; for heavily doped cases, because of the existence of interstitial oxygen ions, it can bring a new absorption band and reduce the radiation hardness of the crystal. 相似文献
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淳于书泰何绍堂 张启仁何安沈华忠 杨上金杜凤英蔡玉琴 顾元元黄文忠庄秀群 龙永录牟丹岷 郭秦孙永良 杨建国彭翰生温树槐 倪元龙余松玉 顾援周正良 毛楚生王世绩刘凤翘 范滇元王树森 陈万年 《中国科学A辑》1992,35(8):875-879
本文在神光装置上,进行了类氖锗X光激光双程放大实验研究.实验中使用了硅/钼多层膜X光平面反射镜.用平场光栅谱仪测量了X光激光的时间积分和时间分辨信号.实验证实了X光激光的双程放大.时间积分结果表明,双程放大为单程放大信号的5倍多;时间分辨结果表明,对多层镜的作用时间作修正后,双程放大信号的增强倍数还要大.在本实验条件下,多层镜的寿命约为400—700ps. 相似文献
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运用相对论的密度泛函离散变分法(DV-Xα)研究了CaWO4晶体中F型色心的电子结构. 计算结果表明,F和F+心在禁带中引入了新的施主能级;分析了晶体内可能存在的光学跃迁模式,并通过过渡态的方法计算了F,F+心跃迁到导带底的能量分别为1.92eV和2.42eV. 因此,从理论上推断了F和F+心在CaWO4晶体中可能引起650nm和515nm的吸收,由此说明CaWO4晶体中650nm和515nm吸收带起源于晶体中的F和F+心.
关键词:
4晶体')" href="#">CaWO4晶体
+心')" href="#">F和F+心
DV-Xα 相似文献
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本文使用差值光吸收谱的测量及谱峰分离技术,测量了掺铁和未掺杂LiNbO3晶体的辐照着色吸收谱及其随辐照剂量的变化规律,并进行比较研究.结果表明:经γ射线辐照处理的LiNbO3;Fe晶体在可见和近红外区产生室温稳定的色心或电荷转移吸收带,它包含了γ射线辐照处理未掺杂LiNbO3中的全部色心吸收带(A,B,C和D),并在B带(2.70eV)长波一侧产生一个新的小吸收带B’(2.45eV).本文认为,2.6 eV附近的宽吸收带系作为基质的LiNbO3晶体本身的辐照缺陷,铁的掺入在LiNbO3中形成Fe2+-VLi偶极子,成为稳定的填隙氧离子陷阱,从而大大增加LiNbO3中色心的增长速率和浓度.并伴生一新吸收带,它可能是由受Ⅰ-Ⅴ偶极子扰动的F+心所产生.此外,还讨论了与铁的掺入有关的其它晶体物理和晶体化学问题. 相似文献
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利用完全势缀加平面波局域密度泛函近似,计算了含铅空位的PbWO4(PWO)晶 体的电 子结构,模拟计算了复数折射率、介电函数及吸收光谱的偏振特性. 比较含铅空位的PWO晶 体与完整的PWO晶体的吸收光谱及其偏振特性,得到与铅空位相关的吸收光谱及其偏振特性 ,计算结果与实验结果基本相符. 计算得到的含铅空位的PWO晶体的光学偏振特性反映了PWO 晶体的结构对称性. 计算结果表明PWO晶体中350,420,550和680 nm的吸收带的出现与PWO 晶体中铅空位的存在直接相关.
关键词:
4晶体')" href="#">PbWO4晶体
电子结构
光学性质
铅空位 相似文献
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