Accurate calculations of the helium atom in magnetic fields

The 1^10^＋ 1^1（-1）^＋and 1^1（2）^＋ states of the helium atom in the magnetic field regime between 0 and 100 a.u. are studied using a full configuration-interaction （CI） approach. The total energies, derivatives of the total energy with respect to the magnetic field and ionisation energies are calculated with Hylleraas-like functions in spherical coordinates in low to intermediate fields and Hylleraas Caussian functions in cylindrical coordinates in intermediate to high fields, respectively. In intermediate fields, the total energies and ionisation energies are determined in terms of Hermite interpolation, based on the results obtained with the two above-mentioned basis functions. Calculations show that the current method can produce lower total energies and larger ionisation energies, and make the two ionisation energy curves obtained with the two above-mentioned basis functions join smoothly in intermediate fields. Comparisons are also made with previous works.

Exact Radial Solution of the Non-relativistic Schrdinger Equation for the Helium Atom with the Potential Harmonic Method

We proposed a simple potential harmonic(PH) scheme for calculating the non\|relativistic radial correlation energies of atomic systems. The scheme was applied to the low\|lying \%n\%\+1\%S\%(\%n\%=1,2) and \%n\%\+3\%S\%(\%n\%=2,3) states of the helium atom. The results exhibit a very stable convergence characterization in both the angular and radial directions with PH and generalized Laguerre functions(GLF) respectively, even though the method is non\|variational one. The ninth significant figure of the non\|relativistic radial energy(NRE) calculated for the ground state exactly agrees with that of the most accurate literature data from the modified configuration interaction method. The convergent NRE′s for the excited states 2\+1\%S\%, 2\+3\%S\% and 3\+3\%S\% with the similar accuracy were also obtained.

Performance of Hyperspherical Harmonic Expansionon the Low-lying P and D States of Helium Atom

The wave functions of the n1,3p (n=2, 3, 4) and the n 1,3D (n=3, 4, 5 ) low-lying states of the helium atom are expanded into the complete sets of the symmetrically adapted basis functions from hyperspherical harmonic functions in the angle part and of generalized Laguerre functions in the radial part respectively, and are then augmented by the simplest type of Jastrow correlation factor to incorporate electron-nucleus cusp only. The excellent agreement between the present nonrelativistic eigen-energies and those from the sophisticated configuration interaction (CI) method for the examined states indicates that the hyperspherical harmonic method can also be applied to the P and the D excited states of the helium atom.

Laser-assisted XUV double ionization of helium atoms:Intensity dependence of joint angular distributions

We investigate the intensity effect of ultrashort assisting infrared laser pulse on the single-XUV-photon double ionization of helium atoms by solving full six-dimensional time-dependent Schrodinger equation with implement of finite element discrete variable representation.The studies of joint energy distributions and joint angular distributions of the two photoelectrons reveal the competition for ionized probabilities between the photoelectrons with odd parity and photoelectrons with even parity in single-XUV-photon double ionization process in the presence of weak infrared laser field,and such a competition can be modulated by changing the intensity of the weak assisting-IR laser pulses.The emission angles of the two photoelectrons can be adjusted by changing the laser parameters as well.We depict how the assisting-IR laser field enhances and/or enables the back-to-back and side-by-side emission of photoelectrons created in double ionization process.

The Zeeman effect for helium atom

The g-factors of the 2 3P, 2 1P, and 3 3P states of the helium atom are calculated by using the vatiational wave functions constructed from the linear combinations of Slater-type basis sets. The relativistic corrections to order α 2(a.u.) and the effect of the motion of the center of mass are treated by using first-order perturbation theory. Most of our predicted results are in good agreement with recent results of Yan and Drake, which were obtained by using the wave functions with doubled Hylleraas coordinates. Based on the analysis of the convergence pattern in our calculation, we believe that our predicted value of the δg L-factor for 3 3P state in 4He, 2.914 15×10 -7 , ought to be reasonable and accurate, although there are no corresponding experimental data available in the liteature yet to be compared with.

A Helium Atom Confined by a Spherical Gaussian Potential Well

氦原子由一个非刺不进的球形的盒子限制了，即，拥有有限高度和范围的一口球形的 Gaussian 潜在的井，被学习采用准确 diagonalization 方法。地面和三个低激动的状态的全部的精力作为限制潜在的半径的功能被获得。我们发现监禁可以与不同低激动的状态和精力价值的倒置引起在层次之间的意外退化。三维的球形的潜在的井和二维的像圆盘的潜力的结果很好与对方相比：一般来说，状态的精力减少，在状态之间的精力间隔与空间尺寸的减小增加。

Four-Parameter Scheme for Ground Level of Helium Atom

在这篇论文，四个参数的扎根的州的波浪函数被开发，当氦原子的 radialSchroedinger 方程被解决时，扎根的州的水平的表达式为氦原子被导出。扎根的精力被 Matlab 7.0 和蒙特卡罗方法的优化算法分别地计算。而且，扎根的州的波浪功能被获得。与有在引用的变化演算的实验值和值相比，这篇论文的结果在四参数的计划显示出那，不是仅仅计算变得更多简化并且精确，而且氦原子的光线的波浪函数处于地面状态自动地遇见空格对称。

Diffusion behaviors of helium atoms at two Pd grain boundaries

The diffusion behaviors of helium atoms at two symmetric grain boundaries (Σ5<001>{210} andΣ3<110> {112}) of Pd were investigated using molecular dynamics simulations through an analytical embedded-atom method(MAEAM) model. The simulations demonstrate that the interstitial helium atoms are easily trapped at the grain boundaries and precipitated into clusters. Due to the closed-shell electronic configurations of both helium and palladium, Pd grain boundaries yield strong capability of retaining helium atoms. By calculating the mean square displacements(MSD) of an interstitial helium atom at the grain boundaries, the diffusion coefficients were determined, and the linear fits to Arrhenius relation. The diffusion activation energies of interstitial helium atom at these two Pd grain boundaries were also evaluated.

The eigenenergies for ~3S excited states of the helium atom with CFPHGLF method

The matrix elements of the correlation function between symmetric potential harmonics were first simplified into the analytical summation of the grand angular momentum. The correlation-function potential-harmonic and generalized Laguerre function method (CFPHGLF) proposed by us recently was then applied to directly solve the Schrodinger equation for n3S(n=2-5) excited states of the helium atom. With only 12 PHs, the convergent eigenenergies of 23S, 33S, 43S and 53S states were 2.17427, 2.06849, 2.03644, 2.02257 Eh, respectively. The errors only were 0.00096, 0.00020, 0.00007, 0.00005 Eh, when compared with the exact Hylleraas variational results respectively.

Numerical studies on the influences of gas temperature on atmospheric-pressure helium dielectric barrier discharge characteristics

A fast-rising gas temperature is due to frequent collisions of the heavy particles in an atmosphericpressure dielectric barrier discharge.In this paper,a two-dimensional fluid model is applied to investigate the influences of rising gas temperature on an atmospheric-pressure helium dielectric barrier discharge.With the increase in the gas temperature,it is found that:(1)a helium discharge can evolve from the discharge column to a homogeneous discharge;(2)the breakdown time is in advance and the gas breakdown voltage decreases;(3)the spatial distribution evolution of the electron density is similar to that of the helium atom density.The most significant discrepancy between them is that the electron densities are high at some positions where the helium atom densities are nevertheless low.Furthermore,the radial reduced electric fields are obtained under different gas temperatures.The physical reasons for the gas temperature effects are discussed.The simulation results provide a better understanding of the roles of the radial reduced electric field and the heavy particle.

Non-sequential double ionization of helium-like atom

In this paper, author investigated the effect of the Coulomb potential of the core of atomic helium on the rescattering processes. Through the calculation author concluded that the Coulomb potential effect may not play an important role in causing the discrepancy between the experimental data and theoretical results of Kuchievs model, and the NS ionization is dependent on the frequency of the laser field. Furthermore, it is concluded that the strength of the laser field and the charge number of the core affect the frequency regime corresponding to the peak value of the NS ionization rate.

Electronic Structure of Helium Atom in a Quantum Dot

Bound and resonance states of helium atom have been investigated inside a quantum dot by using explicitly correlated Hylleraas type basis set within the framework of stabilization method.To be specific,precise energy eigenvalues of bound 1sns(~1S^e)(n=1-6)states and the resonance parameters i.e.positions and widths of^lS^e states due to 2sns(n=2-5)and 2pnp(n=2-5)configurations of confined helium below N=2 ionization threshold of He^+have been estimated.The two-parameter(Depth and Width)finite oscillator potential is used to represent the confining potential due to the quantum dot.It has been explicitly demonstrated that the electronic structural properties become sensitive functions of the dot size.It is observed from the calculations of ionization potential that the stability of an impurity ion within a quantum dot may be manipulated by varying the confinement parameters.A possibility of controlling the autoionization lifetime of doubly excited states of two-electron ions by tuning the width of the quantum cavity is also discussed here.

Atomic origins of solid helium bubbles in tungsten

Solid helium bubbles were directly observed in the helium ion implanted tungsten（W）, by different transmission electron microscopy（TEM） techniques at room temperature. The diameters of these solid helium bubbles range from1 nm to 8 nm in diameter with the mean bubble size about 3 nm. The selected area electron diffraction（SAED） and fast Fourier transform（FFT） images revealed that solid helium bubbles possess body-centered cubic（bcc） structure with a lattice constant of 0.447 nm. High-angle annular dark-field scanning transmission electron microscopy（HAADF-STEM）images further confirmed the existence of helium bubble in tungsten. The present findings provide an atomic level view of the microstructure evolution of helium in the materials, and revealed the existence of solid helium bubbles in materials.

Semiclassical Approach to Non-Sequential Double Ionization of Diatomic Molecules in Strong Laser Field

我们开发一个半古典作品模型描述两价的分子的非顺序的双电离在一强烈线性地极化了成立，在电离动力学完成卓见进 thetwo 电子关联效果。比作氮分子的试验性的数据，我们的模型在在障碍上政体在掘的政体和一个质的协议显示出一个好协议。我们结束古典 collisional 轨道是在掘的政体的双电离的主要来源。作为我们的理论的预言，我们也为氢分子计算 H-2 (2+)/H-2 (+) 的双电离比率并且预言比率不到氮分子的。

Simulation of He Behavior in Metals With Embedded Atom Method

The embedded-atom method(EAM)is used to study the behavior of helium in meta-ls.By fitting the measured parameters such as the activation energy and the heat of solution,the EAM potentials of helium in nickel are extracted.Based upon the EAM potentials,thebinding energy and the self-trapping of helium in nickel are investigated with molecular dynam-ics simulation.

ATOMI射频氦等离子体原子发射光谱用于毛细管气相色谱检测(英文)

There is much different type of selective detectors for GC but emission spectroscopic detectors are few.We developed the radio frequency helium glow discharge plasma detector for capillary GC.It attached polychrometor to detect full spectrum simultaneously and achieved sensitive,selective detection ability for various compounds as a novel element selective detector.The application of this system will be reported.

Variational Calculation of the Doubly-Excited States Nsnp of He-Like Ions via the Modified Atomic Orbitals Theory

In this paper, we have declined the formalism of the method of the Modified Atomic Orbital Theory (MAOT) applied to the calculations of energies of doubly excited states 2snp, 3snp, and 4snp Helium-like systems. Then we also applied the variational procedure of the Modified Atomic Orbital Theory to the computations of total energies, excitation energies of doubly-excited states 2snp, 3snp, 4snp types of Helium-like systems. The results obtained in this work are in good agreement with the experimental and theoretical values available.

基于蒙特卡罗方法的TMSR-LF1功能孔道合金套管的辐照损伤模拟与分析

2 MW液态燃料钍基熔盐实验堆(thorium molten salt reactor-liquid fuel, TMSR-LF1)功能孔道中用于隔离燃料盐的合金套管有7根位于堆中央石墨构件内,受到中子辐照强,辐照损伤大。针对该问题,基于NJOY-2016加工的多群原子离位截面,采用蒙特卡罗程序MCNP对TMSR-LF1中央石墨构件中的合金套管的中子辐照损伤进行了研究,分析了石墨构件中栅元和中心孔道套管的中子注量率分布特点,并根据结果进行了能反应中子辐照损伤量的原子离位数率RDPA和嬗变He产生率的详细计算。计算结果表明,TMSR-LF1堆芯功能套管中RDPA最大值在中心套管的中心平面处,225°方向,为3.0×10^(-9)s^(-1),嬗变He产生率最大值同样发生在中心套管,为2.43×10^(-7)appm·s^(-1)(1 appm=1×10^(6))。研究结论对TMSR-LF1设计和堆芯优化具有重要的实际意义。