等时性质量谱仪中N=Z核质量测量的方法探索

N=Z核的质量数据对于研究rp-和νp-过程至关重要。此外,N=Z原子核的质量数据将会帮助我们解决与核结构有关的许多关键问题。结合碎片分离器的等时性质谱仪（Isochronous mass spectrometry,IMS）是十分快速有效而且高分辨的质量测量工具。由于N=Z核的m/q值非常接近,目前国际上的储存环质量谱仪CSRe/IMP和ESR/GSI还无法实现对N=Z核运用飞行时间谱进行鉴别,因而无法对它们进行质量测量。在日本理化学研究所的仁科加速器中心新建了专用的等时性质谱仪（IMS）,即稀有放射性同位素储存环"Rare-RI Ring"（R3）,以确定短寿命的放射性原子核的质量,其目标质量相对精度为10-6。R3质谱仪与高分辨的碎片分离器BigRIPS的组合,运用束流线的高分辨的离子鉴别,使得R3上的IMS方法对N=Z核进行质量测量成为可能。本文设计了专用的等时性束流光学设置,模拟了124Xe的主束经过碎裂反应产生的N=Z核在束流线中穿过各焦平面的径迹、能量、速度等信息,同时检验了这些次级束在环内的飞行时间相对于动量的变化关系。模拟的结果表明:当储存环的等时性光学设置在某一个N=Z核时,所有其它N=Z核在环内的回旋时间也与动量弥散无关,说明了这些核也满足等时性条件。基于N=Z核的这种等时性的特点,本文对R3上刻度N=Z核的方法也进行了讨论。     

基于4-甲基-3-苯基-5-(2-吡啶基)-1,2,4-三唑的Cu(Ⅱ)、Ni(Ⅱ)和Cd(Ⅱ)配合物的合成、晶体结构及性质

4-甲基-3-苯基-5-（2-吡啶基）-1,2,4-三唑（L）分别与CuCl₂·2H₂O、Ni（NO₃）₂·6H₂O、Cu（ClO₄）₂·6H₂O和Cd（NO₃）₂·4H₂O反应合成了配合物[CuL₂Cl]Cl·H₂O（1）、[NiL₂（H₂O）₂]（NO₃）₂（2）、[CuL₂（H₂O）₂]（ClO₄）₂（3）和[CdL₂（NO₃）₂]·CH₃CN（4）,测定了它们的X射线单晶结构,并用红外光谱、紫外光谱、荧光和热重分析进行了表征。配合物1属于正交晶系,空间群为Fddd,中心离子Cu1（Ⅱ）具有畸变的四方锥构型[CuN₄Cl]。配合物2、3和4都属于单斜晶系,空间群分别为P2₁/_n,P2₁/_n和P2₁/c。配合物2、3和4的中心离子Ni1（Ⅱ）、Cu1（Ⅱ）和Cd1（Ⅱ）都为畸变的八面体构型[NiN₄O₂]、[CuN₄O₂]和[CdN₄O₂]。     

强流离子源光腔衰荡光谱应用研究

强流离子源是托卡马克中性束注入器的核心部件,为了满足未来对高能量离子束中性化效率的要求,负离子源成为中性束注入系统的首选。光腔衰荡光谱(cavity ring-down spectroscopy,CRDS)是一种超高灵敏探测吸收光谱技术。在强流负离子源中,利用氢负离子的光致剥离过程,CRDS可以用来测量氢负离子的绝对积分密度。与激光光致剥离法与光学发射光谱法相比,CRDS具有不受电磁干扰、不依赖等离子体参数、测量精度高等优点。强流离子源负离子密度测量所用CRDS系统由激光器、光学谐振腔、光电探测器和数据采集系统四部分组成。本文根据CRDS测量氢负离子密度的原理,详细推导了氢负离子密度的计算方法,给出了氢负离子密度测算表达式;然后,结合强流离子源实验室应用的具体情况,分析了各部分装置的选择原则与注意事项;最后,介绍了CRDS技术在德国马克斯-普朗克等离子体物理研究所、日本国立聚变科学研究所、意大利Consorzio RFX研究所强流负离子源研究中的应用情况。实验结果表明,源腔气压、源功率等源参数会影响氢负离子密度;铯的注入可以将氢负离子密度从1016 m-3量级提高到1017 m-3量级;同时,日本NIFS的实验结果证明氢负离子密度与引出电流呈线性关系。     

Sixth Harmonic of A Nd：YVO4 Laser Generation In KBBF for ARPES

We report that a deep ultraviolet （DUV） laser from the sixth harmonic of a 1064nm laser has been firstly used as light source in an ultrahigh energy-resolution angle-resolved photoemission spectroscopy （ARPES）. The wavelength is 177.3nm obtained by using the second harmonic KBe2BO3F2 crystal with a frequency tripled 1064nm Nd：YVO4 laser. The large flux （10^14 - 10^15 photons/s） and narrow line width （0.26 meV） are suitable for the ultrahigh-energy resolution ARPES. The laser-ARPES can be a powerful tool to study the electronic structure at and near the Fermi level of the superconductor and correlated materials. The laser-ARPES has worked more than 500 h already.     

Suppression of persistent photoconductivity in high gain Ga2O3 Schottky photodetectors

The defect-related photoconductivity gain and persistent photoconductivity (PPC) observed in Ga₂O₃ Schottky photodetectors lead to a contradiction between high responsivity and fast recovery speed. In this work, a metal-semiconductor-metal (MSM) Schottky photodetector, a unidirectional Schottky photodetector, and a photoconductor were constructed on Ga₂O₃ films. The MSM Schottky devices have high gain (> 13) and high responsivity (> 2.5 A/W) at 230-250 nm, as well as slow recovery speed caused by PPC. Interestingly, applying a positive pulse voltage to the reverse-biased Ga₂O₃/Au Schottky junction can effectively suppress the PPC in the photodetector, while maintaining high gain. The mechanisms of gain and PPC do not strictly follow the interface trap trapping holes or the self-trapped holes models, which is attributed to the correlation with ionized oxygen vacancies in the Schottky junction. The positive pulse voltage modulates the width of the Schottky junction to help quickly neutralize electrons and ionized oxygen vacancies. The realization of suppression PPC functions and the establishment of physical models will facilitate the realization of high responsivity and fast response Schottky devices.     

Manipulating metal-insulator transitions of VO2 films via embedding Ag nanonet arrays

Manipulating metal-insulator transitions in strongly correlated materials is of great importance in condensed matter physics, with implications for both fundamental science and technology. Vanadium dioxide (VO₂), as an ideal model system, is metallic at high temperatures and shown a typical metal-insulator structural phase transition at 341 K from rutile structure to monoclinic structure. This behavior has been absorbed tons of attention for years. However, how to control this phase transition is still challenging and little studied. Here we demonstrated that to control the Ag nanonet arrays (NAs) in monoclinic VO₂(M) could be effective to adjust this metal-insulator transition. With the increase of Ag NAs volume fraction by reducing the template spheres size, the transition temperature (T_c) decreased from 68° to 51°. The mechanism of T_c decrease was revealed as:the carrier density increases through the increase of Ag NAs volume fraction, and more free electrons injected into the VO₂ films induced greater absorption energy at the internal nanometal-semiconductor junction. These results supply a new strategy to control the metal-insulator transitions in VO₂, which must be instructive for the other strongly correlated materials and important for applications.     

含氰基离子液体的合成、表征及流变性质研究

摘要合成、 表征了一系列新的含氰基咪唑类离子液体. 测定了该离子液体的密度、 熔点及溶解性等物理性质, 研究了其在稳态、 瞬态和动态条件下的流变行为. 结果表明, 当剪切速率在0.1～50 s^-1范围内时, 其粘度不随剪切速率的变化而变化, 但随温度升高而降低, 粘流活化能随取代基长度变化呈现规律性变化. 对于1-丁基-3-氰乙基咪唑六氟磷酸盐离子液体, 维持剪切速率不变时, 其剪切应力和粘度均不随时间变化, 且随着温度的升高而降低; 在动态条件下, 在线性粘弹区, 复合粘度和损耗模量G″ 随温度升高而降低. 关键词     

分散固相萃取-液相色谱质谱法测定环境介质中的吲唑磺菌胺及其代谢产物

建立水、土壤和沉积物中吲唑磺菌胺及代谢产物IT-4、IT-15的残留分析方法。环境样品采用QuEChERS前处理方法,并利用超高效液相色谱-串联质谱仪(UPLC-MS/MS)在多反应离子扫描模式(MRM)下进行检测,外标法定量。吲唑磺菌胺及2种代谢产物在一定浓度范围内线性良好(R²≥0.995);添加浓度为0.001～0.1 mg·kg ^-1时,其平均回收率为79.9%～107%,相对标准偏差(RSD,n=5)为0.56%～6.6%;吲唑磺菌胺及2种代谢产物的方法检出限(LOD)为0.01～0.35μg·kg^-1,定量限(LOQ)为0.001 mg·kg^-1.该方法易操作、灵敏度高、重现性好,适用于环境介质中吲唑磺菌胺及代谢产物IT-4、IT-15的快速检测和确证。     

直接基于单元平衡的变截面梁反应分析方法

固定形状的单元位移插值函数不能合理地近似变截面梁内部的位移变化,从而影响了传统梁单元用于计算变截面梁的精度.采用直接基于单元平衡的思想给出了计算变截面梁反应的有限元方法,解决了单元位移插值函数局限性所带来的问题.导出了变截面梁单元的单元刚度矩阵、单元等效节点荷载和单元一致质量矩阵.在此基础上,利用编制的程序进行了算例验证与分析.算例验证了本文理论的正确性,表明本文方法具有很高的计算精度.     

红外透过、反射吸收光谱研究手性液晶(M1)LB膜的结构与取向

利用ＦＴＩＲ光谱研究了一种手性液晶化合物（Ｍ１）ＬＢ膜的结构与取向,该化合物可以形成稳定的单层与多层膜。手性分子中,芳香环平面向于垂直基片表面,分子中的烷基链部分则与基底表面法线方向成一定的角度。