铷原子磁光阱中超冷等离子体的形成和演化

在铷原子的磁光阱中,通过光电离冷原子方法和稠密里德堡原子的自发演化方法产生了超冷等离子体。磁光阱中冷却并囚禁了10^7个原子,温度约为500μK,之后用一束脉冲激光将冷原子电离或者激发至高里德堡态,通过调节脉冲激光的能量控制离子数量或者里德堡原子的数量。利用延迟斜坡电场或脉冲电场引出超冷等离子体中的电子,对超冷等离子体的形成和演化进行了研究,并利用库仑势阱模型对实验结果进行了解释。实验结果表明,由于来自长寿命里德堡原子的贡献,里德堡原子自发演化形成的超冷等离子体的寿命比光电离形成的超冷等离子体的寿命长。     

δ-(Zn,Cr)S(111)表面上的Dzyaloshinsky-Moriya作用:第一性原理计算

根据密度泛函理论的第一性原理计算了具有非中心反演对称的异质结δ-(Zn,Cr)S(111)体系的原子结构和电子结构.Cr原子之间通过第一层S原子传递磁性相互作用.结合广义布洛赫条件,又进一步计算了反方向的自旋螺旋能量与波矢的色散关系E(q)与E(-q).E(q)与E(-q)能量之差反映了δ-(Zn,Cr)S(111)的S层与Cr层之间空间反演对称性破缺引起的DMI的大小.通过海森伯相互作用(HBI)模型与Dzyaloshinsky-Moriya作用(DMI)模型拟合第一性原理计算值,得到了Cr原子间各近邻的HBI参数J_1-J_4与DMI参数d-_1,d_2.在δ-(Zn,Cr)S(111)中,Cr原子间的耦合为M型反铁磁.DMI参数d_1为-0.53 meV,为顺时针手性DMI,在δ-(Zn,Cr)S(111)界面上有可能会产生斯格明子.本文计算表明,磁性和非磁性半导体界面有可能存在DMI,为理论研究和磁存储技术的进步开拓一个新的方向.     

重离子冷却储存环CSRm双电子复合实验研究类锂36,40Ar15+离子同位素移动

配备电子冷却装置的重离子储存环为开展高电荷态离子的双电子复合（dielectronic recombination,DR）精密谱学研究提供了绝佳的实验平台。本工作在兰州重离子加速器冷却储存环主环（HIRFL-CSRm）上开展了类锂36,40Ar15+离子的双电子复合实验,实验观测了电子-离子质心系能量范围为0~35 eV的双电子复合速率系数谱。通过外推法获得了36,40Ar15+离子2s_1/2→2p_1/2和2s_1/2→2p_3/2的跃迁能量。同时利用GRASP2K程序理论计算了36,40Ar15+离子2s_1/2→2p_1/2和2s_1/2→2p_3/2跃迁的质量移动因子和场移动因子,进而得到双电子复合谱的同位素移动值。36,40Ar15+离子2s_1/2→2p_1/2和2s_1/2→2p_3/2同位素移动分别为0.861 meV和0.868 meV。它们均小于目前CSRm上双电子复合实验的实验分辨为~10 meV,进而解释了实验测量的DR谱上未能观察到同位素移动的原因。然而,高电荷态离子的同位素移动场效应与原子序数Z5成正比,因此,在重离子加速器冷却储存环实验环（HIRFL-CSRe）以及未来大型加速器--强流重离子加速器装置（HIAF）上有望通过DR精密谱学方法研究高电荷态重离子甚至放射性离子的同位素移动,进而获得相关原子核的核电荷半径等信息。The cooler storage ring is equipped with an electron-cooler. It is an excellent experimental platform for dielectronic recombination (DR) experiment of highly-charged ions. In this paper, the dielectronic recombination experiments of lithium-like Ar15+ ions with mass number 36 and 40 are conducted at the HIRFL-CSRm(main ring of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou). The experimental electron-ion collision energy scale is from 0 eV to 35 eV. Extrapolation method is exploited to obtain the excitation energies of transitions 2s_1/2→2p_1/2 and 2s_1/2→2p_3/2 of the 36,40Ar15+ ions from experimental data. Meanwhile, GRASP2K program is utilized to calculate the mass shift factors and field shift factors of 36,40Ar15+ ions for 2s_1/2→2p_1/2 and 2s_1/2→2p_3/2 transitions to obtain isotope shifts in DR spectra. In theoretical calculation, isotope shifts of 36,40Ar15+ ions corresponding to 2s_1/2→2p_1/2 and 2s_1/2→2p_3/2 are 0.861 meV and 0.868 meV, respectively. They are both less than the experimental precision (~10 meV) of these dielectronic recombination experiments at the CSRm, which explains that isotope shifts cannot be distinguished from the experimental dielectronic recombination spectra. However, the field shift of highly-charged ions is proportional to Z5. In the future, the dielectronic recombination experiments of highly-charged heavy ions even radioactive ions will be conducted at the HIRFL-CSRe (experimental ring of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou) and the future large accelerator facility--HIAF(High intensity Heavy-ion Accelerator Facility) to measure isotope shifts to obtain the nuclear charge radius information.     

11 MeV能损型质子照相空间分辨能力模拟

透射质子的能损和散射角是质子照相成像模糊的主要来源。基于Zumbro聚焦成像磁透镜的质子照相技术,可基本消除散射角引起的成像模糊,实现几十μm的空间分辨,但无法对能损信息进行优化是其空间分辨能力难以进一步提升的主要原因。为利用透射质子的能损信息,进一步提高质子照相的空间分辨能力,提出了一种新型的成像磁透镜,称之为能损型聚焦成像磁透镜。基于11 MeV低能能损型质子照相的实验束线和Geant4模拟软件,建立全过程照相模型,研究11 MeV能损型成像束线的空间分辨能力。模拟研究表明：对于10 μm厚的Al箔,考虑点扩散函数等测量系统成像模糊的影响,11 MeV能损型成像束线可实现约30 μm的空间分辨。与等大型Zumbro磁透镜相比,空间分辨能力得到显著提升。     

Characteristic improvements of thin film AlGaInP red light emitting diodes on a metallic substrate

We report a type of thin film Al Ga In P red light emitting diode(RLED) on a metallic substrate by electroplating copper(Cu) to eliminate the absorption of Ga As grown substrate.The fabrication of the thin film RLED is presented in detail.Almost no degradations of epilayers properties are observed after this substrate transferred process.Photoluminescence and electroluminescence are measured to investigate the luminous characteristics.The thin film RLED shows a significant enhancement of light output power(LOP) by improving the injection efficiency and light extraction efficiency compared with the reference RLED on the Ga As parent substrate.The LOPs are specifically enhanced by 73.5% and 142% at typical injections of 2 A/cm~2 and 35 A/cm~2 respectively from electroluminescence.Moreover,reduced forward voltages,stable peak wavelengths and full widths at half maximum are obtained with the injected current increasing.These characteristic improvements are due to the Cu substrate with great current spreading and the back reflection by bottom electrodes.The substrate transferred technology based on electroplating provides an optional way to prepare high-performance optoelectronic devices,especially for thin film types.     

Na离子和Cl离子引起He原子直接多重电离过程的研究

利用2～8 MeV的Naq+、Clq+(q=2,3,4,5)轰击氦原子,对碰撞的直接多重电离过程进行研究.实验采用反冲离子-散射离子飞行时间符合技术,通过反冲离子飞行时间谱区分不同价态反冲离子;利用静电偏转和位置灵敏探测技术区分不同电荷态散射离子;结合CAMAC-PC多参数获取系统得到一定价态散射离子所对应的反冲离子电荷态分布谱;经分析该谱得到直接多重电离截面与直接单电离截面之比R21.讨论了R21随入射离子速度和电荷态的变化关系.     

高电荷态Ar^q＋与Ne碰撞中入射离子电荷交换截面的研究

报道Ar^q Ne(q=8，9，11，12)碰撞体系中多电子转移过程，得到了多组实验测量电荷交换截面数据，讨论入射离子电荷交换截面、反冲离子产生截面与入射离子电荷态、能量以及散射离子电荷态的关系，并且将实验结果与Ar^q Ar碰撞体系进行对比研究。在修正分子库仑过垒模型的基础上，对实验现象做了合理的解释。     

自对偶引力的局部对称性与约束

在Ashtekar形式下，广义相对论的相空间被嵌入到复SU（2）Yang-Mils理论的相空间里．将一般场论中分析局部对称性与约束的方法推广到复的场论，从自对偶Palatini形式的位形空间构造出Ashtekar形式的相空间，进而讨论了位形空间上的局部对称性与相空间上的约束的关系． 关键词：     

A Diode-Side-Pumped Dynamic Fundamental Mode Nd：YAG Laser

A fundamental mode Nd：YAG laser is experimentally demonstrated with a stagger pumped laser module and a special resonator. The rod is pumped symmetrically by staggered bar modules. A dynamic fundamental mode is achieved with the special resonator under different pump levels. A maximal continuous wave output of 61 W （M^2 = 1.4） is achieved with a single rod. An average output of 47 W, pulse width of 54 ns, pulse energy of 4.7 mJ and peak power of 87kW are obtained under the Q-switched operation of 10 kHz.     

铈掺杂钆镓铝石榴石相玻璃陶瓷的光学及光谱参数

根据X射线衍射图谱对铈掺杂的钆镓铝石榴石相玻璃陶瓷的晶体结构进行分析,采用直径10英寸积分球结合CCD(charge coupled device)探测器系统,对蓝色半导体发光二极管激发下铈掺杂钆镓铝石榴石相玻璃陶瓷的荧光光谱进行测试,解析出样品发光的绝对光谱功率分布,推导出光量子数分布,求得荧光量子产率和组合白光的色坐标及其相关色温。结果表明,所调查的铈掺杂钆镓铝石榴石相玻璃陶瓷在蓝光LED激发下的荧光量子产率为29.2%,所获得组合白光的色坐标x=0.319,y=0.349,相关色温为6 086K。尽管该混晶陶瓷的荧光量子产率稍小于铈掺杂YAG玻璃陶瓷,但其与蓝光LED组合后发光的色温也明显低于后者,从而为舒适型LED照明玻璃陶瓷的进一步优化提供了新思路。