Energy storage in Ce-doped LiCaAlF6 and LiSrAlF6 crystals

Absorption, emission and thermoluminescence (TL) of as-grown and X-irradiated pure and Ce-doped LiCaAlF₆ (LiCAF) and LiSrAlF₆ (LiSAF) crystals have been analyzed. It is shown that the energy storage is defined by the dissimilarity of basic matrix properties, intrinsic defect structure, preferred Ce³⁺ ion disposition and charge compensation defect type. This is the reason of higher colorability and TL efficiency of as-grown Ce:LiSAF compared to Ce:LiCAF. Pre-filling of ultra-deep traps leads to enormous increases in the TL response. Due to these properties Ce:LiSAF and Ce:LiCAF are promising thermoluminescent dosimetric materials.     

On-line induced absorption measurement on PbWO4, YAlO3:Ce and CsI scintillating crystals

On-line measured radiation-induced absorption spectra and their kinetics are presented for the doped PbWO₄, YAlO₃:Ce and CsI crystals. In the doubly doped PbWO₄:Mo,Y crystals the saturation level of the induced absorption increased with Mo concentration up to 2750 ppm. With a higher concentration it again gradually decreased. Yttrium co-doping around 100 ppm improved considerably the radiation hardness of Mo-doped PbWO₄. Characteristic recovery time of these crystals was about 30 min. Positive influence of Zr⁺⁴ co-doping on characteristics of a set of YAlO₃:Ce samples resulted in decrease in the induced absorption intensity. The presence of very slow recovery processes was in good agreement with thermoluminescence characteristics above room temperature reported earlier. An absorption band round 420 nm appeared in as-grown CsI crystals doped with Tl, and was related to the oxygen contamination.     

Radiation-stimulated defects into LaB3O6 and Li6Gd(BO3)3:Ce single crystals

The radiation-induced defect types in LaB₃O₆ and Li₆Gd(BO₃)₃:Ce single crystals have been determined taking into account crystal-lattice features, absorption characteristics, photo- and thermostimulated luminescence data. The possible activator center models in Li₆Gd(BO₃)₃:Ce crystals are proposed.     

Time-resolved optical absorption in YAlO3 crystals

The present work is devoted to the investigation of transient absorption (TA) induced by a pulsed electron beam (E=250 keV) in pure and doped YAlO₃ (YAP) single crystals. The nature of centers responsible for TA is discussed.     

K5Bi0.9Er0.1(MoO4)4的晶体生长和光学性质

在化学计量的熔料里,用提拉法生长了K₅Bi_0.9Er_0.1(MoO₄)₄单晶。该晶体属于三方晶系,空间群为R3m,z=1.5,晶胞参数为a=6.029?,c=20.823?(六方表示)。晶体具有层状结构,沿着(0001)面容易解理。晶体在室温下的吸收光谱包括有若干条吸收带,它们是稀土离子所特有的。其中三个主要的吸收峰分别相当于从Er³⁺离子的基态 ⁴I_15/2向 ⁴G_11/2, ²H_11/2和 ⁴I_13/2能级的跃迁。本文还给出晶体中相当于 ⁴I_13/2→ ⁴I_15/2跃迁的荧光发射光谱。 关键词：     

Splitting of the near infrared absorption bands of Sm in POCl3:SnCl4, POCl3:ZrCl4 and POCl3:TiCl4

The near infrared absorption spectra of Sm³⁺ in POCl₃:SnCl₄, POCl₃:ZrCl₄ and POCl₃:TiCl₄ consist of a series of bands, attributed to the ⁶H_5/2 → ⁶F_J transitions. Each one of these absorption bands is split into three components. The extent of splitting differs slightly from state to state. For each component of the ⁶F-multiplet the splitting decreases gradually from POCl₃:SnCl₄ to POCl₃:ZrCl₄ and POCl₃:TiCl₄. Energy differences between adjacent components of the near infrared absorption bands vary from a maximum of 166 cm⁻¹ to a minimum of 123 cm⁻¹. The band half-widths of the corresponding components vary from 86 to 120 cm⁻¹. At lower temperatures the intensity of the high energy component increases whereas the intensity of the entire absorption band envelope, associated with each component of the ⁶F-multiplet, remains almost constant. The splitting observed is attributed to the Stark splitting of the ⁶H_5/2-state of Sm³⁺ into three components, in conjunction with appropriate Stark splitting of the states of the ⁶F-multiplet.     

The 3ν3 overtone bands of UF6 and UF6

The absorption specta of CO laser radiation by 3ν₃ overtone bands of ²³⁸UF₆ and ²³⁵UF₆ has been measured using photoacoustic spectroscopic techniques. For the two temperatures 250 K and 290 K, measured absorption coefficients and cross-sections of the 3ν₃ band of ²³⁵UF₆ are reported for the first time.     

Optical absorption of isotopically enriched Li2B4O7 single crystals irradiated by thermal neutrons

Induced absorption spectra in the range 200–900 nm at 77 and 290 K for Li₂B₄O₇ single crystals, isotopically Li and B enriched are presented after irradiation of these crystals by thermal neutrons with fluence 1.8×10¹⁶ cm⁻². The dependence of induced absorption spectra on the isotope composition was revealed: for ⁶Li₂¹⁰B₄O₇ and ⁷Li₂¹⁰B₄O₇ crystals intensive band in the region of 280–294 nm was observed. Under substitution of ⁷Li isotope by ⁶Li in the lithium tetraborate lattice no changes in the absorption spectra were observed. The nuclear reaction ¹⁰B(n,)⁷Li is proposed to be the main mechanism of formation of the radiation defects.     

K5Bi(MoO4)4-Nd3+晶体生长和光学性质

在化学计量的熔料里,用提拉法生长了K₅Bi_0.9Nd_0.1(MoO₄)₄和K₅Bi_0.97Nd_0.03(MoO₄)₄单晶。该晶体属于三方晶系,空间群为R3m,Z=1.5,晶胞常数为a=6.023?,c=20.887?(Nd_0.1)。K₅Bi(Mo 关键词：     

The crystallographic symmetries of single BaPb1−xBixO3 crystals grown from BaCO3-PbO2-Bi2O3 solutions

Single crystals of Perovskite-type oxide BaPb_1−xBi_xO₃ are grown from BaCO₃-PbO₂-Bi₂O₃ solutions which are weighed in two kinds of mixing ratios: X/2 mol % BaCO₃ − (100−X) mol % PbO₂ − X/2 mol % Bi₂O₃ and (10+X/2) mol % BaCO₃ − (90−X) mol % PbO₂ − X/2 mol % Bi₂O₃ These room temperature crystal structures are examined by using an X-ray powder diffraction method. The crystals grown from X/2−(100−X)−X/2 mol % solutions are orthorhombic at room temperature, while the structures are tetragonal with crystals grown from relatively Ba rich and Pb poor ( (10+X/2)−(90−X)−X/2 mol % ) solutions. This result indicates that the difference in the mixing ratio of the initial materials brings about a drastic structural change. The orthorhombic and the tetragonal crystals of x0.25 exhibit superconducting transition at 10K and 12K, respectively. The transition temperature in the latter is 2K higher than the former. In the light of this result, some difference between orthorhombic and tetragonal crystals is considered to influence superconductivity in this system.     

Gd3+/Y3+共掺对Nd:CaF2晶体光谱性能的影响

通过坩埚下降法生长了系列共掺Nd,Gd:CaF₂和Nd,Y:CaF₂晶体, 研究了Gd³⁺/Y³⁺共掺对Nd³⁺光谱性能以及Nd:CaF₂晶体晶胞参数的影响规律. 对于0.5 at.%Nd, x at.%Gd(x=2,5,8,10):CaF₂系列晶体, 当调控Gd³⁺掺杂浓度为2 at.%时, 具有最大的荧光寿命499 μs; 当Gd³⁺掺杂浓度为5 at.%时, 具有最大的吸收截面1.47×10^-20 cm², 最大的发射截面1.9×10^-20 cm²; 当Gd³⁺掺杂浓度为8 at.%时, 具有最佳的发射带宽29.03 nm. 对于0.6 at.%Nd, xat.%Y(x=2, 5, 8, 10):CaF₂系列晶体, Y³⁺掺杂浓度为5 at.%时, 有最大的吸收截面2.41×10^-20 cm², 最大的发射截面3.17×10^-20 cm²; 当Y³⁺掺杂浓度为10 at.%时, 具有最长的荧光寿命359.4 μs,并且具有最大发射带宽26 nm.     

Infrared optical response of YBa2Cu3O7 and PrBa2Cu3O7 An ellipsometric study

Ellipsometry was used to study (110) and (001) oriented films of YBa₂Cu₃O₇ and PrBa₂Cu₃O₇ in the mid-and near-infrared spectral regions. Below a photon energy of 0.1 eV, the in-plane component of the dielectric tensor of YBa₂Cu₃O₇ is dominated by a Drude term with a squared plasma energy of (3.0 ± 0.3) eV². This “oscillator strength”, and the Lorentzian broadening energy of (0.104 ± 0.005) eV at room temperature, are confirmed by the changes induced in Pr-substituted material, and by low-temperature measurements in the near-infrared. The deviation from the Drude behavior observed above 0.1 eV is accounted for by a broad absorption band with an oscillator strength of (3.6 ± 0.1) eV² in YBa₂Cu₃O₇ which shifts to higher energies and takes over almost all of the oscillator strength of the Drude term when Y is substituted by Pr. The response to electric fields perpendicular to the planes is much weaker, with an upper bound of 0.63 eV² for the squared plasma energy. The in-plane loss function computed from the measured dielectric function follows the Drude-like lineshape, modified by the bound-state absorption band, down to the lowest energy reached in our measurements (0.058 eV).     

In2O3晶体电子结构和光吸收机理研究

为了得到准确的In₂O₃晶体电子结构, 本文分别采用GGA, GGA+U, HSE06的方法计算了电子结构, 并进行了G₀W₀修正, 通过比较计算结果, 得到HSE06+G₀W₀方法计算得到的禁带宽带最接近实验结果. 在此基础上使用Hedin的G₀W₀近似方法和Bethe-Salpeter方程计算得到了In₂O₃晶体的光学性质, 计算结果与实验结果吻合很好, 在此基础上通过对准粒子能带结构、光学跃迁矩阵和光学吸收谱的分析, 给出了In₂O₃晶体的光学跃迁机理.     

Nonlinear microwave emission in Ba0.6K0.4BiO3 crystals near Tc

We report a detailed investigation of harmonic generation at microwave frequencies in Ba_0.6K_0.4BiO₃ crystals. Second- and third-harmonic signals are investigated as a function of temperature, external magnetic field and input power level, at temperatures close to T_c. The experimental data are discussed in the framework of a phenomenological theory, based on the two-fluid model, which assumes that the microwave and the static fields, penetrating the sample within the penetration depth, perturb the partial concentrations of the normal and condensate fluids. We show that the enhanced nonlinear effects detected near T_c in Ba_0.6K_0.4BiO₃ and YBa₂Cu₃O₇ crystals may have the same origin. However, in order to account for the experimental data of Ba_0.6K_0.4BiO₃, one needs to involve a distribution of T_c over the crystal.     

Perturbed Al photon echo ENDOR double resonance in Pr:YAlO3 and Eu:YAlO3

Aluminum pure quadrupole spectra measured by photon echo ENDOR double resonance (PENDOR) are reported for crystals of YAlO₃ doped with Pr³⁺ and for crystals doped with Eu³⁺. These spectra, which correspond to aluminum nuclei adjacent to a rare earth impurity, are compared to the results of a conventional NMR study of ²⁷ Al in YAlO₃.     

Effects of Ce3+ energy level structure on absorption and luminescence properties of Ce-doped YAlO3,Y3Al5O12,and LaAlO3 single crystals

We investigate the spectra and scintillation properties of Ce:YA103,Ce:Y₃Al₅O₁₂,and Ce:LaA103.For Ce:YAlO₃,the excitation spectrum is very similar with the absorption spectrum;for Ce:Y₃Al₅O₁₂ and Ce:LaAlO₃,the excitation spectra are different from the absorption spectra.Further,Ce:YAlO₃ has better scintillation performance than Ce:Y₃Al₅O₁₂ whereas Ce:LaAlO₃ has not demonstrated scintillation performance to date.We also provide reasonable explanations for these experimental phenomena from the viewpoint of energy level structure.     

Magnetoresistance of Fe3O4/Au/Fe3O4 and Fe3O4/Au/Fe spin-valve structures

A detailed study of the in-plane magnetotransport properties of spin valves with one and two Fe₃O₄ electrodes is presented. Fe₃O₄/Au/Fe₃O₄ spin valves exhibit a clear anisotropic magnetoresistance in small magnetic fields but no giant magnetoresistance (GMR). The absence of GMR in these structures is due to simultaneous magnetization reversal in the two Fe₃O₄ layers. By contrast, a negative GMR effect is measured on Fe₃O₄/Au/Fe spin valves. The negative GMR is attributed to an electron spin scattering asymmetry at the Fe₃O₄/Au interface or an induced spin scattering asymmetry in the Au interfacial layers.     

Photoinduced dichroism in lightsensitive suspension layers of As2S3 dispersed in gelatin

The absorption edge shift and the spectra of the dichroism in suspension layers of As₂S₃ dispersed in gelatin induced by a linearly polarized laser light are measured. The results are compared to the photoinduced changes in evaporated As₂S₃ layers.     

真空紫外光激发下Ce3+、Tb3+激活的BaCa2(BO3)2的发光性质

利用XRD、VUV及UV光谱等方法对Ce³⁺、Tb³⁺离子掺杂以及Ce³⁺、Tb³⁺离子共掺的3种BaCa₂(BO₃)₂荧光粉的相纯度、发光性质、浓度猝灭现象进行研究。结果表明:3种荧光粉在VUV波段有较好的吸收,基质吸收带位于140～190 nm范围。Ce³⁺在BaCa₂(BO₃)₂的最低4f5d跃迁带位置在360 nm附近,其5d→²F_J(J=5/2, 7/2)发射峰分别位于393,424 nm。Tb³⁺掺杂的样品在172 nm激发下的发射光谱由4个窄带组成,分别对应⁵D₄→⁷F_J(J=3,4,5,6)的跃迁,其中占主导位置的是⁵D₄→⁷F₅的跃迁,大约位于543 nm处,主要为绿光发射。在Ce³⁺,Tb³⁺离子共掺杂的BaCa₂(BO₃)₂光谱中,观察到Ce³⁺-Tb³⁺离子间有能量传递。     

YNbO4：Tm3+/Yb3+上转换发光特性研究

按照50Nb₂O₅-（46-x）Y₂O₃-4Yb₂O₃-xTm₂O₃（x=0.1,0.2,0.5,1,2）的配比方式,采用高温固相法制备出了掺杂Tm³⁺/Yb³⁺的YNbO₄晶体粉末。在980 nm红外光激发下,观测到波长为478,645,707 nm的上转换荧光,分别对应于Tm³⁺离子的¹G₄→³H₆、¹G₄→³F₄、³F₃→³H₆能级跃迁过程。利用上转换发射功率与980 nm激光器工作电流关系估算出跃迁过程吸收光子数目为2.72,2.69,2.01,从而确定出前两者为三光子吸收过程,最后一个对应于双光子吸收过程。运用Judd-Ofelt理论研究样品光谱特性,根据样品的吸收谱得到样品的谱线强度参数Ω_t（t=2,4,6）,进而得出理论振子强度及实验振子强度,二者均方根偏差δ_rms=1.299×10^-7。计算了Tm³⁺离子向下能级跃迁的跃迁几率、跃迁分支比等参数。最后得出结论：（1）³F₄能级寿命较长,适合作为上转换中间能级;（2）³H₅能级寿命较长,且³H₅→³H₆跃迁分支比（96.46%）接近100%,可用于产生1 216 nm激光。