Feature of a Confined Positronium Negative Ion by a Spherical Parabolic Potential

The ground and three low-excited states of the positronium negative ion confined by a spherical harmonic oscillator potential are studied employing the adiabatic hyperspherical approach method. Total energies are obtained as a function of the confined potential radii. We find that the confinement may cause accidental degeneracies between levels with different Iow-excited states and the inversion of the energy values.     

Two-dimensional hydrogen negative ion in a magnetic field

Making use of the adiabatic hyperspherical approach, we report a calculation for the energy spectrum of the ground and low-excited states of a two-dimensional hydrogen negative ion H^{-} in a magnetic field. The results show that the ground and low-excited states of H^{-} in low-dimensional space are more stable than those in three-dimensional space and there may exist more bound states.     

A Study of Confined Helium Atom

The helium atom confined by a spherical parabolic potential well is studied employing the adiabatic hyperspherical approach method. Total energies of the ground and three low-excited states are obtained as a function of the confined potential radii. We find that the energies of a spherical parabolic potential well are in good agreement with those of an impenetrable spherical box for the larger confined potential radius. We find also that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values. The results for the three-dimensional spherical potential well and the two-dimensional disc-like potential well are compared with each other. We find that the energy difference between states in a two-dimensional parabolic potential is also obviously larger than the corresponding levels for a spherical parabolic potential.     

A Study of Confined Helium Atom

The helium atom confined by a spherical parabolic potential well is studied employing the adiabatic hyperspherical approach method. Total energies of the ground and three low-excited states are obtained as a function of the confined potential radii. We find that the energies of a spherical parabolic potential well are in good agreement with those of an impenetrable spherical box for the larger confined potential radius. We find also that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values. The results for the three-dimensional spherical potential well and the two-dimensional disc-like potential well are compared with each other. We find that the energy difference between states in a two-dimensional parabolic potential is also obviously larger than the corresponding levels for a spherical parabolic potential.     

负离子对等离子体鞘层特性影响的数值研究

构造强电负性等离子体中平板电极处鞘层形成的模型,使用流体动力学方程组研究等离子体鞘层.得到空间电势、空间静电荷分布和鞘层宽度作为距离函数的数值结果.结果表明,强电负性鞘层中,在等离子体区和鞘层区之间几乎没有过渡的预鞘区,在靠近极板附近鞘层里的电子、负离子和正离子的分布形成一个纯正离子鞘区.在靠近鞘边附近,空间静电荷密度分布有一个很尖的峰.发现同电正性情形相比,强电负性鞘层的宽度要窄很多,空间电势下降得快得多.     

Energy Spectrum of a Positronium Negative Ion in a Parabolic Quantum Well

The method of few-body physics is applied to calculating the energy levels of low-lying states ofa positro-nium negative ion in a parabolic quantum well. The results show that the energy levels of a positronium negativeion intwo-dimensional case are lower than those in three-dimensional case.     

基于氧负离子PIG源的原子氧产生装置

近地轨道能量为5eV的原子氧对航天器表面影响的地面等效模拟, 是世界各航天国家竟相研究的重要领域. 本文介绍一种基于氧负离子PIG源的原子氧产生装置, 本装置由永磁PIG离子源、两电极引出系统、电子过滤器、单透镜、减速电极和样品架组成. 目前, 这一装置已安装在中国科学院空间科学与应用研究中心小碎片加速器上, 并开展了初步实验. 当离子源放电电流50mA, 在2kV和3kV的引出电压下, 引出的氧负离子分别为200μA和300μA. 并开展了减速实验和kapton膜的溅蚀研究. 由于原子氧装置和小碎片加速器供用同一个靶室. 因此, 这一安排还可以同时开展小碎片和原子氧对空间材料的撞击和侵蚀的研究.     

A Helium Atom Confined by a Spherical Gaussian Potential Well

The helium atom confined by a non-impenetrable spherical box, i.e., a spherical Gaussian potential well which possesses finite height and range, is studied employing the exact diagonalization method. Total energies of the ground and three low-excited states are obtained as a function of the confined potential radii. We find that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values. The results for the three-dimensional spherical potential well and the two-dimensional disc-like potential well are compared with each other： in general, the energies of the states decrease and the energy intervals between states increase with the reduction of the space dimensions.     

Three Charged Bosons Confined in a Harmonic Trap

A system of three charged bosons confined in a harmonic trap has been investigated by an exact diagonalization. We report a calculation for the energy spectrum of the low-lying states of a system of three charged bosons. The important feature of the low-lying states of three charged bosons in a harmonic trap is obtained via an analysis of the energy spectrum.     

Three Charged Bosons Confined in a Harmonic Trap

A system of three charged bosons confined in a harmonic trap has been investigated by an exact diagonalization. We report a calculation for the energy spectrum of the low-lying states of a system of three charged bosons.The important feature of the low-lying states of three charged bosons in a harmonic trap is obtained via an analysis of the energy spectrum.     

Energy Spectrum of Helium Confined to a Two-Dimensional Space

Making use of the adiabatic hyperspherical approach, we report a calculation for the energy spectrum of the ground and low-excited states of a two-dimensional helium in a magnetic field. The results show that the ground and low-excited states of helium in low-dimensional space are more stable than those in three-dimensional space and there may exist more bound states.     

相对论性重离子碰撞中负粒子的横动量和赝快度分布

基于三火球模型和强子共振态衰变图象,得到了相对论性重离子碰撞中负粒子的横动量和赝快度分布,并与200和60GeV/N ¹⁶O与An相互作用的有关实验结果作了比较.     

Re-examining Photodetachment of H~- near a Spherical Surface using Closed-Orbit Theory

Photodeachment of H~-near a reflective spherical surface was studied by Haneef et al.[J.Phys.B:At.Mol.Opt.Phys.44(2011)195004]using a theoretical imaging method.The total cross section displays interesting oscillations.Here we re-examine the total photodetachment cross section of this system by directly applying the standard closed-orbit theory.Our result for the total cross section differs from the result obtained by Haneef et al.The difference between the two results vanishes in the limit of large radius of the reflective sphere.We argue that the theoretical imaging method developed originally for photodetachment near a Hat surface can not be directly applied to the present system.     

Photodetachment of a Negative Hydrogen Molecular Ion near an Interface

Photodetachment of a negative hydrogen molecular ion near an interface is studied by using the two-centre model and the closed orbit theory. The calculation results show that the photodetachment cross section is related to the distance between the two centres in the H₂^- and different molecular ion-interface distances. The comparison between the cross section of H₂^- near an interface with the section of Hˉ shows that at the equilibrium distance of two centres and at low photon energy, the photodetachment cross section of H₂^- is about twice the cross section of Hˉ, which shows that the interference of the two nuclei is very strong; when the distance between the two centres is large, the section of H₂^- is almost the same as the cross section of Hˉ near one interface, which indicates that the interference effect of the two centres anishes.     

强激光场中氘团簇的离子能谱与团簇尺度

在SILEX-Ⅰ装置上进行了超短超强激光与氘团簇相互作用的实验。采用法拉第筒测量了激光与氘团簇靶相互作用后发射出的氘离子能谱,并根据氘离子能谱计算出氘团簇的尺寸和分布。由于激光预脉冲的影响,得到了团簇的尺度比瑞利散射测量的结果小。这些结果对团簇源制备系统的改进和优化激光打靶有着重要的参考意义,而且可以为团簇尺度的测量提供一种新的方法。     

体积产生负氢离子能量沉积及引出效率数值模拟研究

深入研究了负氢离子输运及能量沉积机理,采用全三维蒙特卡罗碰撞方法处理负氢离子与其他粒子间的碰撞,运用CHIPIC软件平台下的PIC(particle-incell)技术处理粒子的储存和磁场约束作用,在此基础上,对JAEA 10 A离子源中体积产生负氢离子输运和散射情景进行了模拟,并分析和讨论了不同气压和过滤磁场对体积产生负氢离子传输和引出特性的影响.结果显示:气压越大,体积产生负氢离子碰撞损耗越大,体积产生负氢离子达到器壁的数量和被引出的数量都越小;低气压放电环境中,过滤磁场对体积负氢离子的引出影响更强烈,且过滤磁场越大,引出效果越差.     

离子束微探针及其扫描断层分析应用研究

以欧共体离子束物理及材料科学研究所的装置为例介绍了离子束微探针实验装置,给出了利用这一装置开展重离子弹性反冲核分析、研究氢在钛合金中的微观分布及其动力学行为的实验结果.该离子束微探针装置可以用来开展带电离子荧光分析、核反应分析、弹性反冲核分析、卢瑟福背散射分析及沟道效应和高离子束密度、大剂量离子注入等分析和研究工作.同时利用微束扫描分析可获得样品中元素的点、线、面分布信息.利用能量为16MeV、直径为3μm的Si5+离子束对钛合金中氢进行断层面扫描分析,观测到了氢在钛合金中的非均匀分布,揭示了氢在钛合金中的不同物理、化学状态与空间分布的相关性,为进一步研究钛的氢化和金属钛的表面腐蚀行为提供了科学依据. As an expmple, the nuclear micro-probe facility in the Forschungszentrum Rossendorf is introduced, which has a minimum beam size of 2 micrometers and can be used to perform particle induced X-ray emission (PIXE), nuclear reaction analysis (NRA), elastic recoil detection analysis (ERDA), Rutherford back scattering (RBS) and channeling etc. micro-beam analyses. By using single point, linear and lateral scanning, the elements composition and distribution in samples can be studied in micrometer scale...     

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。     

Photodetachment Spectrum of Hydrogen Negative Ion Near a Partially Reflecting Spherical Surface

Photodetachment of negative ions near surfaces is of great interest in view of its fundamental significance and technological applications. We reinvestigate the dynamics of photoelectrons in H^? photodetachment near a partially reflecting spherical surface by the semiclassical closed-orbit theory. Reflection parameter R and curvature K is used to observe inelastic and spherical effects of the surface, respectively. The classical action is evaluated from the photodetached electron trajectories incident normally at the surface, arising simultaneously from the source and its image. The derived analytical formula of photodetachment cross section correctly recovers the results of reflective spherical surface published recently based on theoretical imaging method.     

High accuracy calculation of the hydrogen negative ion in strong magnetic fields

Using a full configuration-interaction method with Hylleraas-Gaussian basis function, this paper investigates the 1¹0⁺, 1¹(–1)⁺ and 1¹(–2)⁺ states of the hydrogen negative ion in strong magnetic fields. The total energies, electron detachment energies and derivatives of the total energy with respect to the magnetic field are presented as functions of magnetic field over a wide range of field strengths. Compared with the available theoretical data, the accuracy for the energies is enhanced significantly. The field regimes 3 < γ < 4 and 0.02 < γ < 0.05, in which the 1¹(–1)⁺ and 1¹(–2)⁺ states start to become bound, respectively, are also determined based on the calculated electron detachment energies.