Controlling surface states and photoluminescence of porous silicon by low-energy-ion irradiation

Porous silicon (PS) was irradiated by three kinds of low-energy ions with different chemical activity, namely argon ions, nitrogen ions and oxygen ions. The chemical activity of ions has significant effect on the surface states and photoluminescence (PL) properties of PS, The photoluminescence quenching after argon ions and nitrogen ions irradiation is ascribed to the broken Si-Si bonds, while the PL recovery is attributed to the oxidation of Si-H back bonds. Oxygen ions irradiation leads to the formation of a SiO_x layer with oxygen defects and PS shows different PL evolution than PS irradiated by argon ions and nitrogen ions.     

Sb3+对Tb3+激活硅酸盐玻璃发光性能的影响

利用高温熔融法分别制备了Sb3 ,Tb3 单掺和共掺的硅酸盐发光玻璃,并分析了它们的光谱性质。根据对Sb3 和Tb3 掺杂硅酸盐玻璃的激发光谱、发射光谱和发光衰减时间等特性的分析,研究了澄清剂Sb2O3的加入对Tb3 激活硅酸盐玻璃发光性能的影响。结果表明,在紫外光激发下,Tb3 激活硅酸盐玻璃中存在Sb3 离子至Tb3 离子的能量传递,但能量传递效率较低,能量传递表现为Sb3 离子的3P1能级与Tb3 离子的5D3能级之间的能量无辐射共振转移。同时Sb3 离子的加入将在Sb3 离子和Tb3 离子的激发重叠区域(200～350nm)对Tb3 离子的激发产生不小的负面影响,尚不足以通过Sb3 离子至Tb3 离子的能量传递得以弥补。因此在使用Sb2O3作为Tb3 激活硅酸盐发光玻璃的澄清剂时,应当注意权衡Sb3 离子对Tb3 离子发光性能的影响。     

Pr,Yb:ZBLAN上转换发光过程中的能量传递

详细地研究了Ｐｒ３＋，Ｙｂ３＋ＺＢＬＡＮ玻璃中Ｐｒ３＋和Ｙｂ３＋离子之间的能量传递过程、及能量传递对上转换发光的影响。实验结果表明，在９６０ｎｍ激光泵浦下Ｙｂ３＋通过Ｙｂ３＋—Ｐｒ３＋之间的交叉弛豫向Ｐｒ３＋传递能量。具体的能量传递形式有三种。Ｙｂ３＋作为敏化剂可提高Ｐｒ３＋的上转换发光强度。从Ｐｒ３＋向Ｙｂ３＋的反向能量传递过程也是存在的，具体的过程和Ｐｒ３＋向Ｙｂ３＋传递的相反。Ｐｒ３＋—Ｙｂ３＋的能量传递导致Ｐｒ３＋发光的淬灭，使Ｐｒ３＋上转换发光随着Ｙｂ３＋浓度增加出现饱和。和３Ｐ０能级相比较，Ｙｂ３＋对Ｐｒ３＋离子的１Ｄ２能级发光的淬灭作用更强     

The Calculations of the Concentrations,of the Radial Distributions,and of the Radial Particle Currents of Excited and of Doubly Charged Ions in Low Pressure Discharges

A system of differential equations describing the radial profiles of the number densities and of the radial drift velocities of the ions and of the electrons in positive columns at low pressure containing several species of ions is derived. Excited ions and doubly charged ions, generated in two-step processes by electron impacts, the inertia of the ions and space charge effects are taken into account. For the excited ions de-excitation processes by electron collisions and by spontaneous emission are regarded. A set of nonlinear equations to determine the population densities and the initial values of the differential equations and corresponding boundary conditions are put up. Numerical solutions are given for discharges in argon under free-fall conditions similiar to argon ion lasers. One notices that without stepwise processes via excited ion levels the concentration of double charged ions remains small. In some cases the radial drift of the ions considerably reduces the population of the metastable ion levels. The radial density profiles of the double charged ions and of long-living excited ions considerably deviate from the squared radial profile of the electron density. In addition, for low degrees of ionization the theory of the free-fall column given by Tonks and Langmuir is extended to plasmas containing two species of ions.     

Effects of Ions Charge-Mass Ratio on Energy and Energy Spread of Accelerated Ions in Laser Driven Plasma

Effects of ions charge-mass ratio on energy and energy spread of accelerated ions in laser driven plasma are investigated in detail by proposing a simple double-layer model for a foil target driven by an ultrastrong laser. The radiation pressure acceleration mechanism plays an important role on the studied problem. For the ions near the plasma mirror, i.e. electrons layer, the dependence of ions energy on their charge-mass ratio is derived theoretically. It is found that the larger the charge-mass ratio is, the higher the accelerated ions energy gets. For those ions far away from the layer, the dependence of energy and energy spread on ions charge-mass ratio are also obtained by numerical performance. It exhibits that, as ions charge-mass ratio increases, not only the accelerated ions energy but also the energy spread will become large.     

Reaction of layered sodium disilicate SKS-6 with calcium chloride solution as revealed by solid state NMR spectroscopy: exploring the calcium ion extracting mechanism of SKS-6

Solid-state 1H, 29Si NMR and 23Na MQMAS NMR spectroscopy combined with X-ray powder diffraction (XRD) technique was used to study the reaction between layered sodium disilicate SKS-6 and calcium chloride solution with different concentrations. Based on the experimental results the calcium ion extracting mechanism of SKS-6 was demonstrated to be via ion replacement, during which calcium ions replace sodium ions and combine with the non-bridging oxygen in SKS-6 for charge compensation, and simultaneously sodium ions leave the interlayer. This ion-replacement process was greatly influenced by the substitution of sodium ions by protons as well as the calcium ions concentration. Increasing calcium ions concentration favors the replacement of sodium ions by calcium ions, but prevents sodium ions from being substituted by protons.     

含氘电极真空弧等离子体空间分布特性诊断研究

真空弧放电等离子体含有多种离子成分,并且各离子在空间上具有不同的分布规律.本文针对金属氘化物电极真空弧离子源,搭建了一台紧凑型磁分析装置,用来研究放电等离子体中氘离子与金属离子的空间分布.当离子源弧流为100 A左右时,该装置能有效地传输引出束流,并且具有较好的二次电子抑制效果,可准确获得各离子流强.利用该装置测量并获得了氘化钛含氘电极真空弧放电等离子体内氘离子和钛离子空间分布规律,结果表明:径向上,氘离子和钛离子都呈高斯分布,但氘离子分布均匀,而钛离子相对集中在轴线附近,导致轴线附近氘离子比例最低;轴向上,所有离子数量都以自然指数函数减少,而且相对幅度接近,所以氘离子比例几乎不变.本文研究结果不仅有助于理解真空弧放电等离子体膨胀过程,还可以指导金属氘化物电极真空弧离子源及其引出设计.     

Energy Losses in Collisions of Relativistic Structural Heavy Ions with Atoms

A nonperturbative theory of the energy losses in collisions of structural multiply charged heavy ions moving with relativistic velocities with atoms is worked out. Within the framework of this theory, by structural ions are meant ions containing partially filled electronic shells. It is such ions, having, as a rule, a considerable charge (for example, completely or partially stripped ions of uranium), that are used in many modern experiments on accelerators of heavy ions.     

空心原子的K-x射线谱

报道了利用兰州重离子加速器国家实验室ECR离子源首次引出的全裸Ar离子和类氢、类氦、类锂Ar离子与Be固体表面相互作用形成的空心原子x射线实验测量结果.结果发现，同样条件下，由于K壳层电子的剥离，Ar的K-x射线单离子发射产额增加了5个量级，约为36×10-3每原子；而当L壳层存在电子时，Ar的K-x射线几乎观测不到. 关键词： 高电荷态离子 空心原子 x射线 单离子产额     

Fundamentals of electron-ion interaction

A brief review on the physics of electron-ion collisions is given. After an introduction focussing on the applied importance of electron-ion interactions a discussion of experimental techniques based on colliding beams of electrons and ions follows. The main part deals with the different types of electron-ion collision processes. An overview is provided on (1) electronimpact ionization of ions, (2) electron scattering from ions, (3) electron-impact excitation of ions, and (4) recombination of ions with free electrons.     

Investigation of the luminescence properties and thermal stability of dysprosium,terbium, and europium ions singly- and co-doped strontium yttrium borate phosphors

A series of trivalent rare-earth element ions (europium, terbium, dysprosium) singly- and co-doped strontium yttrium borate phosphors was synthesized via the sol–gel method. The phase formation, luminescence properties, decay times, and energy transfer behaviors from terbium ions to europium ions, the thermal stability, and the Commission Internationale de L’Eclairage coordinates were investigated. Under the excitation of ultraviolet light, the singly doped phosphors exhibited green emission of terbium ions, white emission of dysprosium ions, and red emission of europium ions, respectively. For the terbium and europium ions co-doped strontium yttrium borate samples, a white emission can be realized by blending the doping concentration of terbium and europium ions. The critical distance between terbium and europium ions has been calculated to be about 14.52?Å and the energy transfer from terbium to europium occurred through the dipole–quadrupole interaction. At 150°C, the emission intensity of terbium and europium in the 12?mol% terbium and 14?mol% europium co-doped strontium yttrium borate sample was maintained at about 74% and 87% of their corresponding initial values, respectively, and the dysprosium ions singly doped strontium yttrium borate sample showed about 70% of its initial emission intensity at room temperature. The above results suggested that europium, terbium, dysprosium ions singly- and co-doped strontium yttrium borate phosphors have potential applications as ultraviolet-convertible phosphors.     

Eu~(3+)作探针研究铋铕共掺硼硅酸盐玻璃光学特性

利用高温烧结法制备了铕/铋铕共掺硼硅酸盐玻璃系列样品,测量了样品的激发光谱、发射光谱和声子边带谱,利用Eu3+离子作为探针进一步研究了敏化剂Bi3+的掺入对Eu3+发光的影响.结果表明:本文制作的玻璃样品的电子-声子耦合系数比以往报道过的硼铅等玻璃材料的值都要小,但在硼硅酸盐玻璃中掺入Bi3+会使Eu3+的无辐射跃迁概率增加;Bi3+对Eu3+有敏化作用,Bi3+的掺入使材料的共价性增强,对称性降低,这又使得Eu3+的发光整体变强.所以,在硼硅酸盐玻璃体系中,Eu3+发光的增强不仅仅是由于Bi3+对Eu3+的能量传递,而是以上各因素综合作用的结果.     

Field evaporation of doubly charged ions from a polar liquid

The effect of charge on field evaporation of ions from polar liquids is considered. Using the electromembrane ion source, we performed mass-spectral analysis of field evaporation of ions from the solution of sodium sulfate in a water-glycerol mixture. The composition of doubly charged cluster ions in the field evaporation from glycerol is determined. The rates of the field evaporation of doubly charged ions and singly charged ions are compared. It is shown that the ion charge as well as its localization considerably influences the efficiency of field evaporation of ions from polar liquids.     

30 keV H+在聚碳酸酯微孔膜中动态输运过程的实验和理论研究

测量了30 keV的H⁺入射倾斜角度为-1°和-2°的聚碳酸酯微孔膜后,出射粒子二维分布图、角度分布、相对穿透率以及出射H⁺电荷态纯度随沉积电荷的演化.实验中30 keV的H⁺在微孔膜中输运特性与之前其他能区离子在微孔膜中输运特性有显著不同,实验中直接观测到出射粒子导向部分和散射部分的动态演化过程,出射的H⁺由沿微孔孔轴方向的导向H⁺和沿入射束流方向的散射H⁺两部分组成,随着微孔内电荷斑的沉积,出射的导向H⁺的占比不断减小,出射散射H⁺占比不断增加;出射H⁰占总出射粒子的比例不断减小,其中心方向逐步向入射束流方向偏转.微孔膜处于不同倾斜角度时,微孔内沉积电荷斑的位置和电场强度是不同的.同时模拟计算了入射H⁺在微孔内部的运动轨迹、微孔内部电荷斑电势和场强分布,实验结果和理论结果得到了很好的验证.对出射离子导向部分和散射部分的动态演化过程的观测和理论解释,使得对中能区离子在微孔膜中输运机制有更好的认识.     

表面产生负氢离子引出MCC算法设计

本文深入研究负氢离子输运及引出物理机理,理论分析了交换电荷反应及库仑碰撞过程,并设计了相应数值计算模块.在此基础上,采用有限差分法计算负氢离子所受洛伦兹力,运用蒙特卡罗碰撞方法处理负氢离子与其他粒子间的碰撞,成功研制了表面产生负氢离子输运及引出的全三维MCC算法,结合国外热门离子源JAEA 10A离子源进行模拟验证,结果显示:随着过滤磁场增大,引出离子数越大,离子源空间生存离子总数越小;当过滤磁场较小时,气压越大引出离子数越多,当过滤磁场较大时,气压越小引出离子数越多.     

托卡马克中局域磁扰动引起的高能量离子损失研究

基于单粒子导心运动代码ORBIT，采用测试粒子模拟方法，研究了托卡马克等离子体内部不同径向位置处局域磁场扰动对高能量离子的损失的影响。研究表明，在局域磁扰动主要分布在某磁面附近、其环向具有类似纹波场形式下，可造成一些靠近等离子体中心区域的高能量离子损失，但对靠近等离子边界的离子损失影响相对不大。这些损失的高能量离子均为捕获离子，离子的投掷角越大就越容易损失。此外，造成高能量离子最大损失率的局域场径向位置与这些损失离子的初始径向位置通常存在一定的偏移，而且这个偏移与这些离子的能量密切相关。当局域场出现在某些位置时，能量较低的离子会有一定的损失，能量较高的离子反而不会损失。     

Recent progress on spectral data for X-ray lasers at the NationalBureau of Standards

The Atomic Spectroscopy Group at the National Bureau of Standards is using low-inductance sparks, laser-produced plasmas, and tokamaks to observe spectra that are important for the development of X-ray lasers. Attention is given to recent results on Ne-like ions and ions in neighboring isoelectronic sequences, Ni-like ions and ions in neighboring isoelectronic sequences, and the spectra of rare-gas ions. In addition to contributing to a knowledge of the energy levels and transitions of possible lasing media, the data provide reference lines for wavelength calibration of X-ray laser experiments and reference data for testing theoretical methods used for predicting the properties of lasing ions     

不同成分等离子体鞘层的玻姆判据

在一维平板鞘层中采用流体模型分别研究了不同成分无碰撞等离子体鞘层的玻姆判据.通过拟牛顿法数值模拟了含有电子、离子、负离子以及二次电子的等离子体鞘层玻姆判据.结果表明二次电子发射增加了鞘层离子马赫数的临界值,且器壁发射二次电子温度越高,离子马赫数临界值越小.负离子使离子马赫数临界值减小.而在含有二次电子和负离子的等离子体鞘层中,当负离子较少时,二次电子发射对离子马赫数临界值影响较大;当负离子增加时,离子马赫数的临界值则主要受负离子的影响. 关键词： 鞘层 等离子体 玻姆判据     

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Based on ORBIT code of a guiding center motion of single particle, the loss of energetic ions in different radial positions of tokamak plasma is studied by using test particle simulation method. The results show that the local magnetic perturbations can cause loss of many energetic ions near the central region of the plasma, but they have little effect on the ion loss near the plasma boundary, assuming that the local field is mainly located near a magnetic surface and its toroidal field is similar to the ripple field. These energetic ions are trapped ions, and the greater their pitch angle is, the easier they lose. In addition, the radial position of the local field that causes the maximum loss rate of energetic ions is usually offset from the initial radial position of these loss ions, and this shift is closely related to the energy of these ions. When the local field appears in certain locations, the ions of lower energy have some loss, but the ions higher energy does not lose.     

Influence of the ion charge sign on the stimulation of plasmochemical etching of silicon

The influence of ions with different charge signs on the stimulation of silicon etching under plasma conditions is studied. Fluorine radicals are produced in a glow discharge with a nonuniform pressure. A beam of positive or negative ions is created using a Penning ion source. The flow of fluorine radicals and the ion beam are superposed on a silicon surface placed in a high vacuum. Positive ions may be converted into fast neutrals via resonance charge exchange in the parent gas. It is shown that fast neutrals have the highest catalytic effect. The catalytic effect of positive ions is about two times less. Negative ions occupy the intermediate position. For the first time, it is found that some kinds of ions (e.g., molecular oxygen) do not accelerate, but rather decelerate the etching process; i.e., they behave as inhibitors.