稀土金属La、Nd等在自身氯化物熔盐中溶解过程的研究

本文首次采用实验方法和理论计算相结合，从宏观性质到微观结构进一步深入研究了稀土金属与熔盐的相互作用。藉透明电解槽技术和电化学弱极化方法首次研究了稀土金属La、Nd在各自氯化物熔盐中的溶解过程。采用计算量子化学方法初次计算了金属原子La、Nd等与熔盐中的离子相互作用。并从稀土离子间反应的能量角度讨论了稀土低价离子的稳定性。1）从透明电解槽中观察了金属La、Nd分别在盐Lacl_3+Kcl、NdCl_3kcl体系中溶解时，均产生黑色的金属雾。熔体被金属雾充满而完全不透明分别需要1分半和1分的时间。金属Nd的溶解速度明显快于金属La。其两者的溶解过程可初步认为：1）首先以一些凝聚粒子团进入熔体；2）然后同它们各自熔盐发生化学作用，生成不同价态的离子。经X－射线分析发现熔盐试样中存在La~(2+)、Nd~(2-27+)、Nd~(2-27+)、La~(2+)离子以及Nd、La中性原子。在等摩尔Kcl+Nacl熔盐体系中，金属La、Nd溶解时也将产生黑色的金属雾，但数分钟后，熔体被金属雾充满而呈暗黑色。金属的溶解可能以物理溶解为主。金属Nd在该熔体中的溶解速度也明显大于金属La。以上对La、Nd金属雾的产生过程观察尚未见报道。2）在阴极极化条件下，我们初次发现了金属La、Nd在各自Lacl_3+kcl、Ndcl_3+kcl熔盐中的溶解扩散速度将受到一定程度的抑制，但远不能阻止金属的产生以及扩散于整个熔体中。极化条件下，发现Nd熔体中的金属雾扩散仍然比La熔体中的要快。在等摩尔kcl+Nacl熔盐体系里，阴极极化仍然不能阻止金属Nd的溶解。3）采用电化学弱极化方法首次测定了金属La、Nd分别在Lacl_3+kcl+、Nacl、Ndcl_3+Kcl+Nacl体系中的电化学溶解速度。其自溶解电流密度值分别为:17.4Am/cm~2和29.9Am/cm~2（800℃）以及26Am/cm~2和46.9Am/cm~2(860℃)。增加体系的温度，将有利于金属La、Nd的电化学熔解。金属Nd的电化学溶解速度大于金属La。4）量子化学EHMO计算表明，稀土金属La、Nd、Y溶解于各自熔盐中，不再保持电中性，而是与周围邻近离子发生化学作用，生成低价离子。计算还表明在La~(3+)/Ce~(2+)、Nd~(3+)/Nd~(2+)离子之间，发现有电子云重叠现象。其重叠集居数依次为0.407、1.37和0.18。我们提出有形成原子簇离子的可能。关于La、Nd金属雾呈黑色可根据熔盐中生成的低价离子以及所形成的原子簇离子的吸收光谱性质来加以说明。根据稀土原子的各级电离能，计算了稀土离子（或原子）之间反应的热能。计算表明熔盐中 R_E~(2+)离子较R_E~(1+)离子稳定存在的可能性大。随着La、Ce、Pr、Nd顺序变化，稀土原子与其自身熔盐作用生成低价离子的稳定性趋势增强。这可能是稀土金属在其自身熔盐中的溶解度随La、Ce、Pr、Nd顺序变化而增加的一个缘故。

Near-Infrared Femtosecond Laser for Studying the Strain in Si1-xGex Alloy Films via Second-Harmonic Generation

The second-harmonic generation (SHG) from Si1-xGex alloy films has been investigated by near-infrared femtosecond laser. Recognized by s-out polarized SHG intensity versus rotational angle of sample, the crystal symmetry of the fully strained Si0.83Ge0.17 alloy is found changed from the O-h to the C-2 point group due to the inhomogeneity of the strain. Calibrated by double crystal X-ray diffraction, the strain-induced chi((2)) is estimated at 5.7 x 10(-7) esu. According to the analysis on p-in/s-out SHG, the strain-relaxed Si0.10Ge0.90 alloy film is confirmed to be not fully relaxed, and the remaining strain is quantitatively determined to be around 0.1%.

BAND-STRUCTURE OF MG1-XZNXSYSE1-Y

The empirical pseudopotential method within the virtual crystal approximation is used to calculate the band structure of Mg1-xZnySySe1-y, which has recently been proved to be a potential semiconductor material for optoelectronic device applications in the blue spectral region. It is shown that MgZnSSe can be a direct or an indirect semiconductor depending on the alloy composition. Electron and hole effective masses are calculated for different compositions. Polynomial approximations are obtained for both the energy gap and the effective mass as functions of alloy composition at the GAMMA valley. This information will be useful for the future design of blue wavelength optoelectronic devices as well as for assessment of their properties.

OXYGEN IN INXGA1-XASYP1-Y GROWN ON GAAS

The measurement of DLTS on the alloy InxGa1-xAsyP1-y (0 less-than-or-equal-to y less-than-or-equal-to 0.3; 0.5 greater-than-or-equal-to x greater-than-or-equal-to 0.35) shows a new signal, labeled as E2, with an activation energy of E(c) - 0.61 eV and the SIMS signals show a large number of oxygen. To clarify is further, the energy of the deep level E2 is quantitatively calculated by using Vogl's tight-binding theory and Hjalmarson's deep level theory. As a result, the deep A1-symmetric level associated with an oxygen on the anion site of InxGa1-xAsyP1-y locates deeply in the band gap. Thus, the level E2 is considered to be induced by the oxygen impurity.

Resonant Raman Scattering and Photoluminescence Emissions from Above Bandgap Levels in Dilute GaAsN Alloy

The transitions of E0 ,E0 ＋A0, and E＋ in dilute GaAs（1-x） Nx alloys with x = 0.10% ,0.22% ,0.36% ,and 0.62% are observed by micro-photoluminescence. Resonant Raman scattering results further confirm that they are from the intrinsic emissions in the studied dilute GaAsN alloys rather than some localized exciton emissions in the GaAsN alloys. The results show that the nitrogen-induced E E＋ and E0 ＋ A0 transitions in GaAsN alloys intersect at a nitrogen content of about 0.16%. It is demonstrated that a small amount of isoelectronic doping combined with micro-photoluminescence allows direct observation of above band gap transitions that are not usually accessible in photoluminescence.

LD Side-Pumped Passive Mode-Locked TEM00 Nd:YAG Laser Based on SESAM

We report an LD side-pumped continuous-wave passive mode-locked Nd:YAG laser with a Z-type folded cavity based on a semiconductor saturable absorber mirror (SESAM). The average output power 2.95 W of mode-locked laser with electro-optical conversion efficiency of 1.3% and high beam quality (M-x(2) = 1.25 and M-y(2) = 1.22) is achieved. The repetition rate of mode-locked pulse of 88 MHz with pulse energy of 34 nJ is obtained.

~(143)Nd中高自旋同质异能态的识别与研究

利用能量为 80MeV的18O束流 ,通过130 Te( 18O ,5n)反应研究了143Nd的高自旋态能级结构 .基于γ γ延迟符合、γ射线的角分布及线性极化测量 ,首次发现了143Nd的一个半寿命为 ( 35± 8)ns,自旋和宇称为 4 9/ 2 + 的同质异能态 .用形变独立粒子模型探讨了此同质异能态的形成机制

Multi-quasiparticle gamma-band structure in neutron-deficient Ce and Nd isotopes

The newly developed multi-quasiparticle triaxial projected shell model approach is employed to study the high-spin band structures in neutron-deficient even-even Ce- and Nd-isotopes. It is observed that gamma-bands are built on each intrinsic configuration of the triaxial mean-field deformation. Due to the fact that a triaxial configuration is a superposition of several K-states, the projection from these states results in several low-lying bands originating from the same intrinsic configuration. This generalizes the well-known concept of the surface gamma-oscillation in deformed nuclei based on the ground-state to gamma-bands built on multi-quasiparticle configurations. This new feature provides an alternative explanation on the observation of two I = 10 aligning states in Ce-134 and both exhibiting a neutron character. (C) 2009 Elsevier B.V. All rights reserved.

A study of the suppression of the high-temperature helium embrittlement in an oxide-particle dispersion strengthened alloy

In this paper, an investigation on the micro-structure of an Fe-base oxide-dispersion-strengthened (ODS) alloy irradiated with high-energy Ne-20 ions to different doses at a temperature around 0.5T(m) (T-m is the melting point of the alloy) is presented. Investigation with the transmission electron microscopy found that the accelerated growth of voids at grain-boundaries, which is usually a concern in conventional Fe-base alloys under conditions of inert-gas implantation, was not observed in the ODS alloy irradiated even to the highest dose (12000 at.ppm Ne). The reason is ascribed to the enhanced recombination of point defects and strong trapping of Ne atoms at the interfaces of the nano-scale oxide particles in grains. The study showed that ODS alloys have good resistance to the high-temperature inter-granular embrittlement due to inert-gas accumulation, exhibiting prominence of application in harsh situations of considerable helium production at elevated temperatures like in a fusion reactor.

基于激光诱导击穿光谱技术的铝合金成分定量分析；Quantitative analysis of element concentration in Al alloy by using laser-induced breakdown spectroscopy

利用Nd:YAG激光器输出的532nm激光束对位于空气中的标准变形铝合金样品进行烧蚀产生了激光诱导等离子体.对测量的230—440nm波长范围的光谱进行了谱线标定,同时基于自由定标方法对样品成分进行了定量分析,确定了样品中的元素含量.分析结果与标准值具有较好的一致性.

Quantitative analysis analysis of element concentration in Al alloy by using laser-induced breakdown spectroscopy

Laser-induced breakdown plasma is produced by using Q-switched Nd: YAG laser operating at 532 nm, which interacts with the Al alloy sample target in air. The spectral lines in the 230-440 nm wavelength range have been identified, and based on the calibration-free method, the mass concentration of Al alloy are obtained, which is in good agreement with the standard value of the sample.

Study of a magnetic alloy-loaded RF cavity for bunch compression at the CSR

The Heavy Ion Research Facility and Cooling Storage Ring (HIRFL-CSR) accelerator in Lanzhou offers a unique possibility for the generation of high density and short pulse heavy ion beams by non-adiabatic bunch compression longitudinally, which is implemented by a fast jump of the RF-voltage amplitude. For this purpose, an RF cavity with high electric field gradient loaded with Magnetic Alloy cores has been developed. The results show that the resonant frequency range of the single-gap RF cavity is from 1.13 MHz to 1.42 MHz, and a maximum RF voltage of 40 kV with a total length of 100 cm can be obtained, which can be used to compress heavy ion beams of U-238(72+) with 250 MeV/u from the initial bunch length of 200 ns to 50 ns with the coaction of the two single-gap RF cavity mentioned above.

2.6 s isomer of Nd-129

Nd-129 was produced by irradiation of an enriched target of Ru-96 with a Ar-36 beam and studied by using a helium-jet fast tape transport system in combination with X-gamma and gamma-gamma coincidence measurements. A 2.6s isomer of Nd-129 was observed for the first time and tentatively proposed to be the configuration of 1/2[411].

Two-quasiparticle K-isomeric states in strongly deformed neutron-rich Nd and Sm isotopes: a projected shell-model analysis

Motivated by recent spectroscopy data from fission experiments, we apply the projected shell model to study systematically the structure of strongly deformed, neutron-rich, even-even Nd and Sm isotopes with neutron number from 94 to 100. We perform calculations for rotational bands up to spin I = 20 and analyze the band structure of low-lying states with quasiparticle excitations, with emphasis given to rotational bands based on various negative-parity two-quasiparticle (2-qp) isomers. Experimentally known isomers in these isotopes are described well. The calculations further predict proton 2-qp bands based on a 5(-) and a 7(-) isomer and neutron 2-qp bands based on a 4(-) and an 8(-) isomer. The properties for the yrast line are discussed, and quantities to test the predictions are suggested for future experiment.