抑制BaF2晶体闪烁光慢成分的选择吸收膜系的研究

根据BaF2晶体闪烁光快、慢成分波段的不同，设计并制备了用于抑制该晶体闪烁光慢成分的Al2O3／MgF2／Al／MgF2…金属-介质选择吸收膜系．透射光谱、发射光谱和发光衰减时间谱的实验结果显示，所研制的选择吸收膜系达到了预期的要求，BaF2晶体闪烁光快、慢成分比提高了80倍以上，有效地提高了：BaF2闪烁晶体在高计数率测量中的应用价值．     

纯碘化铯(CsI)晶体的发光与光衰减特性研究

纯碘化铯晶体是一种具有快衰减闪烁特性的新型辐射探测材料, 在伽马射线、中子和其它辐射探测技术中有重要的应用前景。本研究以Bridgman法所生长的纯碘化铯为对象, 分别研究了该晶体的透射光谱以及在紫外光、连续X射线、脉冲X射线和宇宙射线激发下的发射光谱、时间响应特性和沿晶体生长方向不同部位的光输出分布特点。实验测得晶体的吸收边为240 nm, 激发和发射波长分别位于241 nm和318 nm, 发光衰减时间分别为2~3 ns和18~25 ns。以尺寸为30 mm×30 mm×200 mm的晶体籽晶端和尾端与PMT耦合所测得的光输出分别是143 p.e/MeV和127 p.e./MeV, 尽管晶体两端的光输出存在12.6%的差异, 但没有观察到衰减时间长于100 ns的慢分量。这些性能进一步证明纯碘化铯晶体具有作为快闪烁体的优势。     

彩色照相冲扩设备技术原理及操作维护（2）

彩色照相冲扩设备技术原理及操作维护（２）上海八一电影机械厂张仁清６．光的计量简述光度计量主要有：发光强度、光通量、光照度、光亮度等四项。（ａ）发光强度（简称光强），是表示光源发光强弱的物理量。代表符号１；单位是坎德拉。ｄ；１９７９年第１６届国际计量大...     

永冲电化学腐蚀制备n型多孔硅及其发光性能

采用脉冲电化学腐蚀法,以n型单晶硅为衬底制备多孔硅（n—PS）,通过扫描电镜（SEM）、室温500—700nm范围内荧光光谱,系统研究腐蚀时间、占空比和脉冲频率对n-PS的结构形貌和可见光区室温光致发光特性（PL）的影响,结果表明,相比直流电化学腐蚀方法,脉冲腐蚀能获得孔径分布均匀且发光强度更高的多孔硅;随腐蚀时间、占空比和脉冲频率等腐蚀条件的变化,其发光峰位及发光强度均有明显改变;当等效腐蚀时间为30min、占空比为0．5、脉冲频率为10Hz时,制备的n—PS的PL强度较高,发光性能较好。     

Mo^6＋，Gd^3＋，PbF2组合掺杂对钨酸铅发光的改善和光谱分析

坩埚下降法生长了（Mo^6＋、PbF2），（Mo^6＋、Gd^3＋），（PbF2，Gd^3＋）组合掺杂，及PbF2单掺杂钨酸铅晶体，对样品进行了吸收光谱、光产额、x射线和紫外激发发光光谱等测试和表征，讨论了掺杂对钨酸铅发光的增强效果。掺杂钨酸铅总发光额都得到了增强；在门宽100ns内晶体的光产额都有提高，但在测试门宽在200ns内，（Gd^3＋、PbF2）掺杂样品光产额有所下降。x射线激发发光显示，PbWO4：（Mo^6＋、Gd^3＋）的蓝发光和绿发光分量都有提高；PbWO4：（Mo^6＋、PbF2）蓝发光受到拟制，提高了绿发光成分，晶体光学吸收边明显红移。PbWO4：（Gd^3＋、PbF2）蓝发光得到增强，绿发光得到一定的拟制。光致发光光谱分析表明，Gd^3＋掺杂对PbWO4基质发光有敏化作用。实验证实，F在PbWO4生长中非常不稳定，显示很差的掺杂均匀性。     

Bridgman法生长的PWO晶体的发光特性和透光特性

本文采用改进的Bridgman法，以纯度不低于99．99％的PbO和WO3为原料，生长出无色透明的、大尺寸的PbWO4（PWO）晶体，研究了晶体沿生长方向不同部位的透射光谱及X射线激发的发射光谱特性．发现改进的Bridgman法生长的PWO晶体具有较好的发光均匀性和透光均匀性，其原因主要是改进的Bridgman法采用密封的坩埚，有效地抑制了组份（PbO和WO3）的挥发.     

纳米包覆法制备SrAl2O4：Eu^2＋，Dy^3＋发光粉及铁杂质猝灭研究

利用纳米包覆技术制备了掺杂不同含铁量的发光粉SrAl2O4：Eu^2＋，Dy^3＋通过透射电子显微镜（TEM）研究了纳米氧化铝水合粒子的包覆过程。通过X射线衍射（XRD）、光谱测量等分析手段研究了铁杂质对发光粉}生能方面的影响。结果表明，微量铁的引入没有使发光粉的晶相结构发生变化，但却大大降低了其发光强度。随着铁含量从0．001mol增加到0．01mol，余辉平均发光强度下降了50％，这种变化可能是由于Fe^3＋-O^2-知中心将一部分能量传递到红外区域引起的，同时首次发现了铁在铝酸锶晶体中的红外发光现象。     

钨酸铅(PbWO_4)晶体的发光均匀性研究

通过对下降法生长的全尺寸钨酸铅（ＰｂＷＯ４）晶体沿长轴方向不同点的透过率和光产额的测量、分段晶体的透过率和光产额的测量,研究了钨酸铅晶体的发光均匀性及其影响因素．结果表明：钨酸铅晶体发光均匀性主要由生长后期的钨酸铅晶体质量所决定,采用晶种为大头的加工取向有利于提高钨酸铅晶体的发光均匀性．     

低分子量无规聚丙烯与商用聚丙烯复合材料的紫外荧光性能

通过将分子量无规聚丙烯（LMWAPP）与商用等规聚丙烯（IPP）共混,研究其发光性能,结果表明,低分子量无规聚丙烯对聚丙烯的发光起着重要作用,着聚丙烯中LMWAPP含量的增加,聚丙烯发光强度增加,当LMWAPP含量超过30％时,发光强度达到饱和。     

提供安全出口专用荧光粉

二．技术简介 电致（场致）发光可分为交流粉末电致发光（现介绍交流粉末电致发光）、直流电致发光、注入式电致发光。又分为有机电致发光（OEL）和无机电致发光（EL）。电致发光现象根据最早报道又名“予击穿发光现象”，其发光机理是在高倍电子显微镜下观察到的许多带有正负电荷的发光线。在一定电场频率周期激发下每个晶体的电子离子发生陷阱和碰撞产生发光现象。细粒度：5微米左右。     

Ultrafast electronic relaxation and charge-carrier localization in CdS/CdSe/CdS quantum-dot quantum-well heterostructures

The relaxation and localization times of excited electrons in CdS/CdSe/CdS colloidal quantum wells were measured using subpicosecond spectroscopy. HRTEM analysis and steady-state PL demonstrate a narrow size distribution of 5-6 nm epitaxial crystallites. By monitoring the rise time of the stimulated emission as a function of pump intensity, the relaxation times of the electron from the CdS core into the CdSe well are determined and assigned. Two-component rise times in the stimulated emission are attributed to intraband relaxation of carriers generated directly within the CdSe well (fast component) and charge transfer of core-localized carriers across the CdS/CdSe interface (slow component). This is the first reported observation of simultaneous photon absorption in the core and well of a quantum-dot heterostructure. With increasing pump intensity, the charge-transfer channel between the CdS core CdSe well contributes less to the stimulated emission signal because of filling and saturation of the CdSe well state, making the interfacial charge-transfer component less efficient. The interfacial charge-transfer time of the excited electron was determined from the slow component of the stimulated emission build-up time and is found to have a value of 1.2 ps.     

Auger-free luminescence of the BaF2:Sr, BaF2:MgF2 and CsBr:LiBr crystals under excitation of VUV photons and high-energy electrons

The emission spectrum, the time dependence of the luminescence, the excitation spectrum and the reflectance spectrum have been measured for the pure BaF₂ crystal, the BaF₂:Sr crystals with Sr⁺⁺ concentrations of 2 and 5 mol%, the BaF₂:MgF₂ crystal with a mole mixing ratio of 1:2, and the pure CsBr crystal and the CsBr:LiBr crystal with a mole mixing ratio of 1:1. The measurements have been made by using synchrotron orbital radiation and high-energy electrons produced by gamma-rays. It is shown that the BaF₂, the BaF₂:Sr and the BaF₂:MgF₂ crystals have the Auger-free luminescence having decay times around 0.90 ns. The slow and fast luminescence components of the BaF₂ crystal are suppressed by introduction Sr⁺⁺ and Mg⁺⁺ ions. It is, however, clearly seen that the suppression of the slow component is more effectively occurring than that of the fast component, especially in the BaF₂:MgF₂ crystal. By analyzing the Auger-free luminescence spectrum, it is shown that the valence band widths are 2.7 ± 0.3 eV, 2.7 ± 0.3 eV and 4.2 ± 0.3 eV and the band-gap energies are 11.1 ± 0.3 eV, 11.1 ± 0.4 eV and 11.9 ± 0.4 eV for BaF₂, BaF₂:Sr and BaF₂:MgF₂ crystals, respectively. The introduction of LiBr into CsBr has resulted in a significant enhancement in the luminescence intensity, attaining 40 times larger intensity than that of CsBr crystal at room temperature, due to the suppression of the non-radiative relaxation of the outer-most core holes due to the absorption induced by the Urbach effect. The observations of the increases in the band gap-energy, the exciton energy and the decay time of the CsBr:LiBr crystal compared with those of the CsBr crystal support the argument given in the present study regarding the suppression of the Urbach effect in the CsBr:LiBr crystal. The decay times observed are 0.20 ± 0.05 ns and 0.90 ± 0.06 ns for CsBr and CsBr:LiBr crystals, respectively.     

A note on the application of BaF2 scintillators to γ-ray and charged particle detection

Two practical aspects of the application of BaF₂ crystals as detectors for nuclear radiation are considered: (1) wavelength shifting of the fast UV light component by a thin p-terphenyl layer, and (2) identification of light charged particles by measuring the intensity ratio between the fast and slow light components. Experimental tests have yielded satisfactory results in both directions.     

快速闪烁晶体在未来高能物理实验中的应用

简要综述了快速闪烁晶体在未来高能物理实验中的应用和目前研究进展.在未来高亮度强子对撞机（HL LHC）上通过采用高亮度、快速和高抗辐照强度的LYSO晶体为CMS的量能器升级,可以建成具有良好E/γ能量分辨率的稳定的精密电磁量能器.通过读取PbF2,PbFCl和BSO晶体中的切伦科夫光和闪烁光,可以为未来的轻子对撞机建立具有良好的喷注能量分辨率的均匀强子量能器.有亚纳秒衰变时间的BaF2晶体将为未来的高能物理强度前沿实验建立在速率及时间分辨率提高超过10倍的晶体量热器.对新型快闪烁晶体如PbFCl,YAP:Yb,ZnO:Ga和CuI的研究可能为今后高能物理实验发挥重要作用.     

Mechanoluminescence glow curves of rare-earth doped strontium aluminate phosphors

The present paper reports the mechanoluminescence (ML) glow curves of rare-earth doped strontium aluminate phosphors. When Sr₃Al₂O₆:Eu, Dy phosphor mixed in epoxy resin is compressed at a fixed pressing rate or fixed strain rate, its elastico ML (EML) intensity increases linearly with deformation time or pressure and attains a maximum value I_m at the time t_m, at which the deformation is stopped. Under the pressed condition, the decay time for fast decrease of EML after t_m, gives the time-constant for stopping the cross-head of the testing machine used to deform the sample, and decay time for slow decrease of EML gives the lifetime of electrons in the shallow traps lying in the normal piezoelectric region of the crystals. When SrAl₂O₄:Eu phosphor mixed in resin is compressed at a fixed rate, then the EML intensity increases linearly with pressure and when the pressure is decreased at a fixed rate, then the EML intensity decreases exponentially with time, in which the decay time of EML is equal to the lifetime of electrons in the shallow traps lying in the normal piezoelectric region of the crystals. The EML intensity of SrAl₂O₄:Eu film excited by the impact stress, initially increases with time, attains a peak value and later on it decreases exponentially with time, in which the fast decay of EML intensity gives the decay time of impact stress and the decay time of the slow decrease of the EML intensity gives the lifetime of electrons in the shallow traps lying in the normal piezoelectric region of the crystals. The piezoelectrically-induced detrapping model is found to be suitable for the EML of rare-earth doped strontium aluminate phosphors. Expressions derived on the basis of the piezoelectrically-induced detrapping model are able to explain satisfactorily the characteristics of the EML of the phosphors. It is shown that several parameters of the phosphors can be determined from the ML glow curves.     

γ-CuI晶体的发光衰减时间和对X射线的能量响应

采用溶剂蒸发法生长出透明的带隙宽度为2.96 eV的γ-CuI晶体。在紫外光激发下, 该晶体在410、430 nm处分别呈现有近带边发射峰, 另在720 nm附近还出现一个与样品碘缺陷有关的宽发射带。经碘退火后, 样品720 nm发射带被基本抑制, 而在420 nm处出现了一个更强的近带边发射峰。使用扫描相机分别测量了γ-CuI晶体各发射峰(带)的衰减时间谱, 其中近带边发射峰的发光衰减时间常数均在数十皮秒量级, 表明γ-CuI晶体具有极快的时间响应特性; 而720 nm发射带的发光衰减时间常数主要在数十纳秒量级。X射线激发下, γ-CuI晶体具有435 nm近带边发射峰和680 nm发射带, 其近带边发射对X射线能量响应的测量结果表明, 当E_X<49.1 keV时, γ-CuI晶体闪烁光快分量对X射线的探测效率相对较高。     

Pulsed cathodoluminescence of calcite crystals of various origins

We have studied the luminescence of calcites from phlogopite-calcite veins, marbles, leucogranites, apatite-calcite ores, and carbonatites in the spectral range 300–800 nm under excitation with nanosecond electron pulses at an electron beam current density of ∼10 A/cm². All of the calcite varieties have a fast emission component, with a broad spectrum in the near-UV and visible spectral regions, whose decay time is comparable to the excitation pulse duration, and a slow emission component, with a peak-emission wavelength of 610–620 nm and decay time of tens of milliseconds. The spectral composition of the emission depends on the nature of the calcite sample. We analyze the evolution of the spectrum after excitation and discuss the luminescence excitation mechanisms and the nature of the emission centers.     

Emission of opal photonic crystals under pulsed laser excitation

Infiltration of opal with nonlinear optical materials is shown to markedly raise its emission intensity in the visible range under pulsed laser excitation. Evidence is presented for three-photon parametric scattering in both uninfiltrated and infiltrated globular photonic crystals, with excitation of “slow” photons in the visible range. Our results indicate that synthetic opal crystals can be used as photon traps for studying the emission spectra of organic and inorganic materials infiltrated in opal pores.     

A study on yttrium doping in lead tungstate crystals

In this paper we present results of a study on the yttrium doping in lead tungstate crystals. The crystal growth by modified Bridgman method is described. Results of trace analysis on raw materials and crystals are presented. The segregation coefficient of yttrium ions in lead tungstate crystals was determined. The scintillation emission and longitudinal transmittance spectra, light output, decay kinetics, light response uniformity and radiation damage were measured. It is found that yttrium doping suppresses slow scintillation component and improves radiation hardness of lead tungstate crystals.     

Scintillation properties of Tm-doped Lu3Al5O12 single crystals

Using the micro-pulling-down (μ-PD) method, Tm-doped Lu₃Al₅O₁₂ (Tm:LuAG) single crystals were grown to examine their scintillation properties. In transmittance spectra, they exhibited about 80% transparency in the wavelengths longer than 320 nm and five absorption lines due to Tm³⁺ 4f–4f transitions were observed. ²⁴¹Am α-ray excited radioluminescence spectra were measured and intense 4f–4f emission peaks were observed with the host emission. When excited by ¹³⁷Cs γ-Ray to obtain pulse height spectra, Tm 1% doped LuAG showed the highest light yield coupled with a photomultiplier (PMT) or a silicon avalanche photodiode (Si-APD). The light yield was estimated to be 5800 and 7300 photons/MeV for PMT and Si-APD, respectively. Decay time profiles consist of two exponential components and the fast and slow components are considered to be attributed to the host and the combination of the host and Tm³⁺ 4f–4f emission, respectively.