ZBLAN玻璃中Pr3+掺杂离子3P0和1D2能级的发光特性和寿命

对ZBLAN氟锆酸盐玻璃中Pr³⁺掺杂离子³P₀和¹D₂能级的寿命和发光特性进行了较详细的光谱学研究。首先测量了两种掺杂浓度(质量分数分别为1×10^-3,5×10^-3)的Pr³⁺:ZBLAN玻璃的吸收光谱,然后运用时间分辨激光光谱技术测量了³P₀和¹D₂能级在激光单光子共振激发下的荧光发射谱和能级寿命。将不同荧光发射谱带的强度和文献报道的Judd Ofelt理论计算辐射跃迁几率数值做了比较分析,证明了文献中理论计算结果的可靠性。由于浓度猝灭效应,在相同的激发条件下,掺杂浓度为1×10^-3样品的荧光发射强度明显大于5×10^-3样品的荧光发射强度。但是从我们的测量结果看,掺杂浓度对³P₀和¹D₂ 的能级寿命值无显著影响。掺杂浓度为1×10^-3时,Pr³⁺离子³P₀和¹D₂能级的寿命值分别为46,322μ_s。     

PrxLa1-xP5O14的发光理论和浓度效应

本文利用Judd-Ofelt理论求得PrP₅O₁₄晶体的振子强度参数Q₂,比较了计算和实验的振子强度,计算了³P₁,³P₀,¹D₂和¹G₄能级的电偶极和磁偶极辐射跃迁几率及¹D₂→¹G₄和³H₄→³F₄能级对间的多极矩耦合的无辐射迁移几率。讨论了¹D₂能级发射强度的浓度效应。并且,给出¹D₂能级发射强度的表达式和强度随着浓度和单位时间内激发光引起的³H₄到¹D₂跃迁的诱导跃迁几率的变化图。 关键词：     

THE 82S1/2→62D EXCITATION TRANSFER OF RUBIDIUM ATOMS INDUCED BY COLLISIONS WITH GROUND-STATE RUBIDIUM AND HYDROGEN MOLECULES

The processes of excitation transfer from the 8²S_1/2 state to the 6²D state of rubidium in Rb(8²S_1/2)-Rb(5²S_1/2) and Rb(8²S_1/2)-H₂ collisions have been studied experimentally. During irradiating the Rb vapor, mixed with H₂, by two light beams for selective stepwise excitation, the Rb 8²S_1/2→5²P_3/2 direct fluorescence and the Rb 6²D_3/2→5²P_1/2 sensitized fluorescence have been measured as a function of H₂ gas pressure. The measurements yielded the cross-sections σ(8²S_1/2→6²D) and σ^*(8²S_1/2→6²D) of Rb 8²S_1/2→6²D excitation tranfer induced by collisions with 5²S_1/2 atom and H₂ molecules respectively. The results are discussed in detail.     

TmP5O14晶体的上转换发光的研究

报道室温下TmP₅O₁₄晶体在脉冲DCM染料激光激发下产生的紫外和深紫色上转换发光现象.测量发现在300—500nm波长范围内主要有两组上转换荧光,一是较强的¹D₂→³H₆,³F₄的360和450nm的双光子荧光,另一是¹I6→³F₄的347nm的三光于荧光,发现了由 关键词：     

124Te核1+态和高自旋态能谱特征的微观研究

利用微观sdIBM-2+2q.p.方案，成功地计算出¹²⁴Te核的低自旋态和部分高自旋态，特别是较成功地再现了1⁺₁,1⁺₂,3⁺₁，3⁺₂和5⁺₁态.基于该方案推出的能量关系指认：6⁺₁，8⁺_{关键词： 能谱特征 拆对与顺排 微观sdIBM-2+2q.p.方案 124Te核')" href="#">¹²⁴Te核}     

243—263nm S原子Rydberg态的(2+1)共振增强多光子电离

在243—263nm波长范围,测量了S⁺分质量激发谱,得到SO₂分子光解产生的S原子近50条(2+1)共振增强多光子电离谱线．除了来自S原子基态3p⁴³P_2,1,0直至n=10的Rydberg态³P,³D,³F的许多双光子跃迁谱线外,观察到若干新的¹P⁰,⁵S^关键词：     

Tm3+离子掺杂的钨酸钇钠晶体中浓度猝灭效应的研究

测量了Tm³⁺离子不同浓度(0.5at.%, 3 at.%, 5 at.%)掺杂的NaY(WO₄)₂晶体在800nm激光二极管激发下的上转换发射光谱.结合吸收谱、荧光谱和由Judd-Ofelt理论计算的光谱参数，详细分析了Tm³⁺:NaY(WO₄)₂晶体中上转换能量传递机理和离子浓度对上转换发射的影响.讨论了四种影响上转换发光效率的离子间相互作用机理：³H₅+¹G₄→³H₆+¹D₂，³H₅+³H₅→³H₆+³F₃，¹G₄+³H₆→³F₄+³F₃，¹G₄+³H₆→³F₃+³F₄，并根据Miyakawa-Dexter理论定量计算了各过程的发生概率.论证了交叉弛豫和共协上转换等浓度猝灭效应是影响Tm³⁺离子蓝色上转换荧光发射效率的主要因素. 关键词： 3+离子')" href="#">Tm³⁺离子 4)₂晶体')" href="#">NaY(WO₄)₂晶体 上转换 浓度猝灭     

Pr3+在SBN晶体中的发光特性

通过测量Ｐｒ：ＳＢＮ晶体的吸收光谱和荧光光谱来确定Ｐｒ³⁺在ＳＢＮ晶体中的能级位置。由于Ｐｒ³⁺离子占据晶体中的不同格位而引起荧光带呈现双峰结构。测量荧光寿命随温度的变化关系，表明Ｐｒ³⁺在ＳＢＮ晶体中 ³Ｐ₀态的无辐射弛豫主要是 ³Ｐ₀→¹Ｄ₂多声子弛豫过程。 关键词：     

直接键连原子间的NMR偶合常数的自然杂化轨道研究IV、13C-15N和13C-19F核自旋偶合常数1JCN和1JCF

首次报道了直接计算偶合常数¹J_CN和¹J_CF的线性关系式,结果表明,¹J(CN)和¹J_CF主要由成键原子的轨道杂化作用和键极性这两种结构因素所决定,且偶合相互作用中的Fermi接触项仍是最主要的.为从简单价键理论角度解释并计算J_CN和J_CF的值提供了简便直观的方法.     

有机磷化合物的NMR研究——Ⅱ0,0-二烷基膦酸酯的1H、13C和31PNMR谱

本文报道了21个0,0一二烷基膦酸酯类化合物的¹H、¹³C和³¹P NMR参数。研究和讨论了不等价的二烷基¹H、¹³C化学位移和磷碳偶合常数与立体化学的关系。测定了(CH₃CH₂O)₂P(O)CH(CH₂NO₂)(p-OCH₃C₆H₄)的¹³C自旋一晶格弛豫时间T₁,二乙基¹³C T₁间的差别,说明在类似化合物中,含有化学位移各向异性对弛豫的贡献。     

Methods for correlating T1rho and FID components in wideline 1H NMR studies of motionally heterogeneous polymer systems

We address the problem of correlating the observed FID and T_1ρ components in wideline ¹H relaxation measurements of motionally heterogeneous polymers, and show that different methods of data treatment can highlight different aspects of the correlations present. For a sample of polypropylene we find that the T_1ρ relaxation behaviour is driven by relaxation associated with the intermediate FID component, which strongly suggests a motionally inhomogeneous amorphous region in the sample.     

氟哌酸1HNMR的测定及过渡金属离子对其影响

氟哌酸^*[即1-乙基-6-氟-4-氧-7-(1-哌嗪)-3-(1,4-二氢化喹啉甲酸]是一种广谱、安全、有效、可供口服的抗感染药。我们测定了它的¹H自旋-晶格弛豫时间T₁及其在Cr³⁺、Mn²⁺、和Fe³⁺等过渡金属离子存在下的T₁值。实验结果表明,在加入过渡金属离子前后,氟哌酸不同位¹H的T₁值发生了一定的变化。据此可揭示过渡金属离子和氟哌酸形成配合物的配位点,从而可确定所形成配合物的结构。     

固体高分辨NMR研究PPU/PMAs,AB-交联聚合物中的分子运动和相容性

本文使用固体高分辨NMR测量了PPU/PMAs,AB-交联聚合物中PPU的侧甲基的¹³C自旋-晶格弛豫时间(T₁)。使用内旋转运动的平均谱密度函数分析了PPU侧甲基的内旋转和PMA的侧基的多重内旋转运动。结果表明PMA中的侧基距主链越远,其旋转速度越快并且PPU侧甲基的内旋转速度随ABCP中PMA侧链长度增加而变快。还使用质子的T_1ρ和T₂及自旋扩散研究了体系的相容性和相行为。得到了有关相应尺度下的每相的组成和软相微区尺度的信息。     

大分子中磁偶极弛豫的分离

提出采用仅与偶极弛豫有关的¹³C核同¹H核之间的核交叉弛豫速率来考察分子内部运动状况。给出了实际用于考察分子运动状况的关系式,从理论上阐明了本文方法比传统上直接采用常规测定的¹³C核纵向弛豫时间T₁、演向弛豫时间T₂及NOE增强因子η来研究分子运动状况的方法要合理。建立了既适用于小分子又适用于大分子自旋系统¹³C核总自旋弛豫中偶极弛豫分离的公式.     

H NMR study of YT2-hydride (T = Fe, Mn)

In the hydrides YMn₂H_3.0, the nuclear magnetic resonance of ¹H nuclei has been measured under external fields up to 50 kOe at 4.2 K and three ¹H NMR signals have been observed. The ¹H hyperfine fields corresponding to these NMR signals can be discussed in terms of the dipole interaction between the H nuclei and the localized moments of the Mn(or Fe) atoms surrounding H atoms.     

14N核四极共振自旋系统自旋-晶格弛豫时间的测量

¹⁴N核四极共振自旋系统的自旋-晶格弛豫是一种双指数弛豫。本文介绍了¹⁴N核四极共振自旋系统的自旋-晶格弛豫时间的3种测量方法,利用可变多面体方法对实验数据进行拟合,获得了¹⁴N核四极共振自旋系统的自旋-晶格弛豫时间T_1s和T₁₁,对有关文献中关于核四极共振弛豫时间的测量的3个观点提出了质疑。     

T2 relaxation time histograms in multiple sclerosis

An accurate measurement of the transverse relaxation time T₂, and the histogram of T₂ in the brain parenchyma can be accomplished in vivo using a multi-echo magnetic resonance imaging sequence. An estimate of the error in the T₂ measurement is derived using copper sulfate doped water phantoms. Correction factors are calculated and applied to the signal intensity of each voxel prior to the in vivo T₂ evaluation. These corrected T₂ are in good agreement with the theoretical values calculated from copper sulfate concentrations. This technique is then applied to calculate T₂ histograms of the brain. The population studied was composed of normal volunteers and multiple sclerosis patients. The corrected T₂ histogram method discriminates the normal control population from the MS population, and also discriminates between relapsing-remitting patients and primary progressive or secondary progressive patients. Moreover using this approach we are able to detect in MS patients a global shift of the T₂ of the white mater toward higher values. The results of this study showed that the method is easy to implement and may be used to characterize MS pathology.     

Proton dynamics in letovicite, (NH4)3H(SO4)2: a 1H and 14N NMR spectroscopic study

The improper ferroelastic phase letovicite (NH₄)₃H(SO₄)₂ has been studied by ¹H MAS NMR as well as by static ¹⁴N NMR experiments in the temperature range of 296–425 K. The ¹H MAS NMR resonance from ammonium protons can be well distinguished from that of acidic protons. A third resonance appears just below the phase transition temperature which is due to the acidic protons in the paraelastic phase. The lowering of the second moment M₂ for the ammonium protons takes place in the same temperature range as the formation of domain boundaries, while the signals of the acidic protons suffer a line narrowing in the area of T_c. The static ¹⁴N NMR spectra confirm the temperature of the motional changes of the ammonium tetrahedra. Two-dimensional ¹H NOESY spectra indicate a chemical exchange between ammonium protons and the acidic protons of the paraphase.     

H double-quantum filtered MR imaging of joints tissues: bound water specific imaging of tendons, ligaments and cartilage

The ¹H double-quantum filtered (DQF) NMR and DQF MRI is applied to the joint tissues of rabbits for selective visualization of tendons, menisci and articular cartilage. The ¹H DQF NMR selectively filters double-quantum coherence arising from the ¹H dipolar interaction of the “bound” water in these tissues. The double-quantum creation time dependency of the DQF signal intensity is determined by the molecular environment of the “bound” water. Therefore, each tissue has a unique creation time at which the DQF signal reaches its maximum intensity, τ_max (Achilles tendon: 0.46 ± 0.02 ms, patella: 0.55 ± 0.8 ms, anterior cruciate ligament: 0.60 ± 0.05 ms, meniscus: 0.78 ± 0.02 ms, skin: 0.81 ± 0.07 ms). We have presented the creation-time-contrasted DQF images of the meniscus, patella, foot, and knee joint. Compared with conventional T₂*-weighted gradient-echo (GRE) MR images, tendons, ligaments, menisci, and articular cartilage were more clearly seen in the DQF MR images. All these tissues were distinctly discriminated from each other by their creation times. DQF MR images of foot and knee joints can selectively demonstrated tendons, ligaments, and cartilage, which make it easier to understand the complicated anatomic structure of joints. Because the DQF NMR signal intensity and τ_max are sensitive to the order structure of the “bound” water, it might be possible to introduce the creation-time dependent-contrast of ¹H DQF MR images as a new tool for analyzing the changes in the ordered structure of the tissue.     

通过HSQC和1H,13C-COSY叠合增强二维谱分辨率的方法

通常二维谱F₁维分辨率较差,F₂维分辨率较好. 即HSQC实验¹³C维度分辨率较差,¹H维度分辨率较好. 而¹H, ¹³C-COSY实验¹³C维度分辨率较好,¹H维度分辨率较差. 提出一种通过HSQC和¹H, ¹³C-COSY叠合,取较弱的值储存并显示的方法增强分辨率,采用Bruker Topspin软件AU程序实现. 该方法在不明显增加采样时间的情况下,可显著增强分辨率,信噪比也没有降低. 同时抑制了F₁噪声. 处理后,谱图美观清晰.