共查询到18条相似文献,搜索用时 297 毫秒
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本文从实验上系统地研究了在不同条件下电子束辐照LiF晶体所形成的F3+色心的光学特点。并且由荧光光谱分析了F3+心和F2心,的相对密度关系。实验表明,辐照温度对于色心的形成和密度的相对大小起着关键的作用。主要实验结果包括:1)在液氮温度下辐照,然后在暗处加热至室温可形成高密度的F3+心,表现在发射光谱中F3+心荧光占绝对优势。吸收光谱表明没有N心和R心。2)由动力学荧光谱可以看到低温辐照的样品在F2+心衰变的同时,F3+心密度迅速增加。而室温辐照的样品则是F2心,与F3+心的密度以近似相等的速率增加。3)详细观察了F3+心530nm荧光激发带与F2心670nm荧光激发带半宽度的变化和双峰结构。由此对M吸收区的发光特点作了解释。
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通过高温固相法分别制备了CaWO4和CaWO4:1%Eu3+ 样品. 测量了样品不同温度(10–300 K)的荧光光谱、荧光衰减曲线和 时间分辨荧光光谱. 样品的荧光光谱表明: 在240 nm紫外光激发下, 两个样品在430 nm处都展现出来源于WO42-的蓝色发射; 样品CaWO4:Eu3+的Eu3+(5D0→7F1, 2, 3,4)的特征发射则归属于WO42-到Eu3+ 间的能量传递.由样品室温(300K)荧光衰减曲线发现: 纯CaWO4的荧光寿命为8.85μs,Eu3+掺杂之后WO42-的荧光寿命缩短至6.27μs,这从另一方面证明了WO42-与Eu3+间能量传递的存在. 由荧光寿命得到T=300K时, CaWO4: 1%Eu3+中WO42-与Eu3+间的能量传递效率(ηET)为29.2%, 能量传递速率(ωET)为4.65×104 s-1.通过时间分辨荧光光谱, 获得了从WO42-到Eu3+之间的能量传递的时间演变过程,当温度由10 K增加到300 K时, 能量传递出现的时间单调变小. 测试了不同温度(10–300 K)对CaWO4:Eu3+的荧光寿命的影响, 发现在10–50K时,Eu3+的荧光寿命增加, 但温度超过50K时发生猝灭, 荧光寿命开始下降; WO42-的荧光寿命则是随着温度的升高逐渐缩短.
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能量传递
红色荧光粉
温度依赖
4:Eu3+')" href="#">CaWO4:Eu3+ 相似文献
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利用发展的调制俘获损耗荧光光谱技术实验测量了超冷铯分子0u+(6P3/2)长程态的高灵敏光缔合光谱. 光谱探测范围较国际已有报道扩大了60 cm-1, 观察到25个长程区域新的振动能级. 通过LeRoy-Bernstein公式对振动束缚能数据进行拟合, 获得了超冷铯分子0u+(6P3/2)态的长程系数C3 为16.103±0.010. 构建了超冷铯分子0u+(6P3/2)态长程区域的势能曲线. 相似文献
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在0—7GPa静压范围内测量了自发有序Ga0.5In0.5P合金的室温光致发光谱.三块样品的常压带隙能量分别比无序样品低115,92和43meV,它们的压力系数也从无序样品的92meV/GPa分别减小到75,81和83meV/GPa.用Γ-L相互作用模型可以同时解释有序合金的带隙能量的降低以及压力系数的减小.得到的Γ-L相互作用势分别为0.19,0.15和0.10eV.表明在自发有序Ga0.5In0.5P合金中存在着的 相似文献
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F. Damay Z. Jirák M. Hervieu C. Martin A. Maignan B. Raveau G. André F. Bourée 《Journal of magnetism and magnetic materials》1998,190(3):221
The structural and magnetic transitions in Pr0.5Sr0.41Ca0.09MnO3 have been investigated by neutron diffraction and electron microscopy. Two structural transitions, Imma to I4/mcm and I4/mcm to Pmmn, are observed by decreasing the temperature. Two magnetic transitions, from a paramagnetic insulating to a ferromagnetic metallic and from a ferromagnetic metallic to an antiferromagnetic insulating states at TC=250 K and TN=180 K, respectively, are also observed. The structures of these three forms have been determined from neutron powder diffraction data. The first important result concerns the low temperature antiferromagnetic CE type and charge ordered structure, which has been refined in the Pmmn space group, without any constraint. This structure is completely long range ordered, with two Mn-sites, Mn3+ in tetragonally elongated octahedra, and Mn4+, off-centered in nearly regular octahedra. The second important point concerns the abrupt character of the structural transition from the I4/mcm to the Pmmn structure, without any appearance of incommensurability. The magnetic and transport properties of this compound are compared with those of Pr0.5Sr0.5MnO3. 相似文献
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We have investigated perovskites with composition Sr2Na0.5Ln3+0.5WO6 and Sr2Na0.5Ln3+0.5 UO6 (Ln = La, Gd, Eu). Their luminescence gives information on crystallographic details of the crystal structure and on a number of different energy transfer phenomena in these compounds. For Ln = La the Na+ and La3+ ions are disordered; for Ln = Gd(Eu) they are ordered. Single-step energy transfer is observed for the couples U6+ -Eu3+ and W6+ - Eu3+; energy migration occurs within the uranium and the europium sublattices. 相似文献
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G.C. Lie Sigrid D. Peyerimhoff Robert J. Buenker 《Journal of Molecular Spectroscopy》1982,93(1):74-82
Dipole moment functions, both perpendicular and parallel to the molecular axis, are calculated from the SCF and MRD-CI results of a previous study for the normal ν2 bending vibrations of HCN and DCN. Vibrationally averaged dipole moments and the infrared transition matrix elements are then obtained from the dipole moment functions and vibrational wave functions. MRD-CI results, with known experimental values in parentheses, for HCN are 〈0|μ|0〉 = ?2.954(?2.985) D, 〈1|μ|1〉 = ?2.915(±2.942) D, 〈0|μ|1〉 = 0.148(0.147) D, 〈0|μ|2〉 = ?0.027 D, 〈1|μ|2〉 = 0.210 D. Calculated absolute intensities at 1 atm and 0°C for the (0200) ← (000), (0200) ← (010), and (0220) ← (010) bands of HCN are 25 (40 ± 10 as estimated from spectra), 8.5, and 17.0 atm?1 cm?2, respectively. Results for DCN are also reported. 相似文献
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Yiping Guo Ken-ichi Kakimoto Hitoshi Ohsato 《Journal of Physics and Chemistry of Solids》2004,65(11):1831-1835
We report that ferroelectric-relaxor behavior is induced by doping of SrO and TiO2, or BaO and TiO2 into classic ferroelectric (Na0.5K0.5)NbO3. It is found that [(Na0.5K0.5)0.9Sr0.1](Nb0.9Ti0.1)O3 ceramics exhibit a pronounced ferroelectric-relaxor behavior, comparable to that of [(Na0.5K0.5)0.9Ba0.1](Nb0.9Ti0.1)O3 ceramics. Our results indicate that the relaxor behavior is closely related to the appearance of micropolar regions in these systems. The relaxor behavior should arise from the dynamic response of micropolar clusters. Raman spectra of [(Na0.5K0.5)1−xSrx](Nb1−xTix)O3 ceramics measured in the wavenumber range from 100 to 1200 cm−1 confirm that the first order scattering is dominant in phonon bands should result from both short-range ordered region (micropolar regions) and disordered matrix. The frequency dependence of dielectric permittivity measurements show that the relaxor behavior of SrO and TiO2, or BaO and TiO2 doped (Na0.5K0.5)NbO3 ceramics is not a Debye type in the radio frequency range. 相似文献
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Nabil Kallel Nejib Ihzaz Sami Kallel Ahmed Hagaza Mohamed Oumezzine 《Journal of magnetism and magnetic materials》2009,321(15):2285-2289
The structural, magnetic and transport properties of La0.5Sr0.5MnO2.88 and La0.5Sr0.5Mn0.5Ti0.5O3 samples have been investigated systematically. Indeed, this series has been considered to understand the influence of physical parameters such as oxygen deficiency and titanium doping effect in undoped La0.5Sr0.5MnO3 sample. Ceramic material based on La0.5Sr0.5MnO2.88 exhibits interesting behaviours of charge-ordering (CO), ferromagnetic (FM) states and a good conductivity down to the lowest temperatures. The substitution of Ti for Mn destroyed drastically the CO, damaged the motion of itinerant eg electrons and changed the local parameters of perovskite cell. A change of the structure from tetragonal to rhombohedral symmetry is observed causing a weakening of double-exchange interaction. The experiment results show that the suppression of the CO is sensitive to the variety of Mn3+/Mn4+ ratio. In a field of 8 T at 10 K, FM and CO phase can be evaluated to be ∼20:80 according to the μexp/μcal ratio for La0.5Sr0.5MnO2.88, whereas the CO state is suppressed for La0.5Sr0.5Mn0.5Ti0.5O3 sample, FM and anti-ferromagnetic (AFM) phase are coexisted and evaluated to be ∼54:46, respectively. 相似文献
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M. Kamimura 《Nuclear Physics A》1981,351(3):456-480
All the multipole transition densities between the seven T = 0 states in 12C are calculated with the use of the microscopic 3α resonating-group wave functions which are obtained by dynamically solving the 3α relative motion with the total antisymmetrization taken into account exactly. The observed elastic and inelastic electron scattering form factors for the transition to the 21+, 41+, 02+, 11?and 31? states are well reproduced with no additional effective charge. The existence of a deformed intrinsic state for the 01+, 21+and 41+states is deduced by the analysis of the transition densities between them which are derived by the weak-coupling-type 3α wave functions; the intrinsic density distribution is illustrated. The monopole density distribution of the 02+, 22+ and 11?, states is found to be much longer ranged than that of the 01+, 21+ and 41+ states; the 31? state case is intermediate. On the basis of the transition densities between the 01+, 21+, 02+ and 22+ states, analysis is made of the transition between the shell-like states and the molecule-like states with a large spatial-structure change. Specific, effective nucleon-nucleon interactions are folded into the transition densities here obtained. The evident dependence of the radial shape of the folded nucleon-12C form factors on the choice of the interactions and the multi-step form factors for the excitation of the 02+, 11? and 31? states are discussed. 相似文献