Synthesis of (7-polyfluoroalkyl)pyrazolo[1,5-a]pyrimidines based on lithium fluorine-containing β-diketonates

The reactions of Li enolates of fluorine-containing -diketones with 3-aminopyrazoles afforded (7-polyfluoroalkyl)pyrazolo[1,5-a]pyrimidines. The structure of 3-bromo-2-methyl-5-phenyl-7-trifluoromethylpyrazolo[1,5-a]pyrimidine was established by X-ray diffraction analysis.     

Li- and P NMR spectra of cyclopentanone lithium enolate in ethereal solvents: identification of the HMPA-coordinated aggregate structures

The structures of cyclopentanone lithium enolate under HMPA titration in 0.04-0.8 M diethyl ether and dimethyl ether solvents have been investigated using the low-temperature ⁷Li, ³¹P, and ¹³C NMR. The progressive solvation by HMPA occurs for the tetra- and dimeric enolates, and upon addition of >2 equiv. of HMPA, the lithium enolate has been converged on a mixture of tetra-HMPA coordinated tetramer and bis-HMPA coordinated dimer with the ratio of 5:95 and <1:99 in diethyl ether and dimethyl ether, respectively. Neither monomeric nor trimeric enolate is detectable under such HMPA titration.     

Li2B4O7晶体生长及其二次谐波系数

用恰克拉斯基（Ｃｚｏｃｈｒａｌｓｋｉ）法特殊工艺生长出尺寸为Φ３０×３０ｍｍ的优质Ｌｉ２Ｂ４Ｏ７单晶，讨论了工艺参数对晶体宏观缺陷的影响。用Ｍａｋｅｒ条纹测量了晶体的二次谐波系数ｄ３１和ｄ３３，结果表明，Ｌｉ２Ｂ４Ｏ７的ｄ３３是石英晶体ｄ１１的三倍。     

电池正极材料中Li+运动特性的7Li NMR研究

利用变温⁷LiNMR实验对Li-电池正极材料LiMn₂O₄和LiCoO₂中Li⁺的运动特性进行了研究,结果表明,随实验温度的提高,LiMn₂O₄的⁷LiNMR谱线窄化,表明其中Li⁺迁移能力增加,而LiCoO₂的谱线无变化.此外随温度提高,LiMn₂O₄的⁷Li的T₁变短,而LiCoO₂的T₁变长,产生这种不同变化趋势的原因在于LiMn₂O₄和LiCoO₂晶相结构的差异造成其中Li⁺迁移能力的差别,它们各自的相关时间τ_c使⁷Li核的T₁分别位于T₁-τ_c曲线极小点两侧.     

Conversion of VUV to UV and visible in K5Li2LnF10 containing rare-earth from cerium group (Ln=La, Ce, Pr, Nd)

The potential of single crystals K₅Li₂LnF₁₀, for applications as VUV excited phosphors has been examined. The crystals were doped with lanthanide ions (Ce³⁺–Nd³⁺) with concentrations up to 100 at%. The self-quenching of luminescence is strongly reduced in this material. Luminescence spectra in the 50,000–10,000 cm⁻¹ range and excitation spectra in the 40,000–250,000 cm⁻¹ spectral range have been recorded at room and low temperature. Intense visible emission has been observed for Nd³⁺ and Pr³⁺. For the Pr³⁺ ions strong the ¹S₀–¹I₆ transition has been recorded only for concentrated crystals. Efficient conversion of VUV excitation to UV–VIS emission was observed in crystals doped with 3 and 100 at% of cerium. In both cerium-activated crystals the lifetimes of f–d transitions were equal to 32 ns.     

Nature of correlations in the atomic limit of the boson fermion model

Using the equation of motion technique for Green's functions we derive the exact solution of the boson fermion model in the atomic limit. Both (fermion and boson) subsystems are characterised by the effective three level excitation spectra. We compute the spectral weights of these states and analyse them in detail with respect to all possible parameters. Although in the atomic limit there is no true phase transition, we notice that upon decreasing temperature some pairing correlations start to appear. Their intensity is found to be proportional to the depleted amount of the fermion nonbonding state. We notice that pairing correlations behave in a fashion observed for the optimally doped and underdoped high T_c superconductors. We try to identify which parameter of the boson fermion model can possibly correspond to the actual doping level. This study clarifies the origin of pairing correlations within the boson fermion model and may elucidate how to apply it for interpretation of experimental data. Received 31 January 2003 / Received in final form 18 March 2003 Published online 23 May 2003 RID="a" ID="a"e-mail: doman@kft.umcs.lublin.pl     

锂分子31Πg里德堡态的光谱研究

我们用脉冲光学-光学双共振荧光激发谱(OODR),测量了在35 500～38 000 cm-1能量范围内的里德堡态,观察到7Li231Πg态的10个振动能级.本文对观测的31Пg态的146条激发谱线进行了归属,得到了新的Dunham常数,RKR势能曲线以及A1Σ+u到31Πg态跃迁的夫兰克-康登因子,并且讨论了31Πg态的双重分裂以及与附近里德堡态F(4)1Σ+g,51Σ+g,61Σ+g和G(2)1Πg的微扰.发现在我们的实验精度下(0.2 cm-1) 31Πg态的双重分裂可以忽略.     

氢化非晶硅薄膜的电场诱导锂离子注入及其光伏特性

采用电化学方法，在电场诱导下，对氢化非晶硅（ａ－Ｓｉ：Ｈ）薄膜进行锂离子注入，并用光电化学方法对不同条件下处理的ａ－Ｓｉ：Ｈ薄膜的光伏性质和注入机理进行了研究。结果表明，处理电位小于－０．６０Ｖ时，理离子注入明显，经过注入的薄膜光伏响应提高６０％左右．     

Photocurrent measurement in chemically deposited CdS: Li films

The dependence of photocurrent on the light intensity in CdS:Li films formed by chemical bath deposition technique is studied. The superlinearity observed is explained on the basis of increased lifetime of the photoexcited electron. The effect of oxygen adsorption in the film surface on the lifetime of the electron is studied.     

Short‐circuit current improvement of CuGaSe2 solar cells with a ZnS/(Zn,Mg)O buffer combination

CuGaSe₂ (CGS) thin‐film solar cells were prepared with an in‐line co‐evaporation process and the established buffer combination CdS/i‐ZnO was replaced by ZnS/(Zn,Mg)O. We obtained functional CGS solar cells with a strong gain in the short‐circuit current density as compared to the CdS/i‐ZnO buffer reference cells. The enhanced current density is a result of improved transmission in the wavelength region between 330 nm and 550 nm of the ZnS/(Zn,Mg)O buffer combination as compared to CdS/i‐ZnO. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)