A Theoretical Study of Pure and Mixed Spin-Polarized Tritium and Helium Triatomic Systems Using Hyperspherical Coordinates

Pure and mixed spin-polarized tritium ( ${{\rm T}\uparrow}$ ) and helium (He) triatomic systems are studied using hyperspherical coordinates. A slow variable discretization approach is adopted to solve the nuclear Schrödinger equation, in which the Schrödinger equation in hyperangular coordinates is solved using basis splines at a series of fixed FEM-DVR hyperradii. By using the best empirical interaction potentials, we study comparatively the bound states of ( ${{\rm T}\uparrow}$ )₃, ⁴He( ${{\rm T}\uparrow}$ )₂, ${^4{\rm He}_2{\rm T}\uparrow}$ , ⁴He₃ and ${^4{\rm He}_2^3{\rm He}}$ in the J ^Π = 0⁺ symmetry. The bound state energy levels are calculated for all these molecular species except ⁴He( ${{\rm T}\uparrow}$ )₂, for which we have found no bound state. The calculated wave functions of these species are found all to exhibit a very large spatial extension, indicating the diffuse nature of these bound states. The molecular structure of these species will also be calculated and analyzed in detail.     

Group Theoretical Calculation for Infrared Spectra of Triatomic Molecules

The rotation-vibration levels of the molecule COS are described using the model U(5). The transition matrix elements for the molecular levels are calculated by means of a group theoretical approach. The infrared absorption line intensities for the molecule COS are calculated. The results are in good agreement with the experimental values. Copyright 2001 Academic Press.     

A Self-Consistent Model for Positronium Formation from Helium Atoms

The differential and total cross sections for electron capture by positrons from helium atoms are calculated using a first-order distorted wave theory satisfying the Coulomb boundary conditions. In this formalism, a parametric potential is used to describe the electron screening in a consistent and realistic manner. The present procedure is self-consistent because (a) it satisfies the correct boundary conditions and post–prior symmetry, and (b) the potential and the electron binding energies appearing in the transition amplitude are consistent with the wave functions describing the collision system. The results are compared with the other theories and with the available experimental measurements. At the considered range of collision energies, the results agree reasonably well with recent experiments and theories.     

Cascade Calculation of Exotic Hydrogen Atoms Involving Kinetic Energy Evolution

The cascade calculation of the π^?-p atom has been done. The acceleration and deceleration processes are added in standard Borie–Leon's model, and the kinetic energy evolution is completely considered. The X-ray yields and the kinetic energy distribution are investigated.     

The Hyperfine Structure of the Ground State in the Muonic Helium Atoms

Non-relativistic ionization energies ³He²⁺μ^?e^? and ⁴He²⁺μ^?e^? of helium-muonic atoms are calculated for ground states. The calculations are based on the variational method of the exponential expansion. Convergence of the variational energies is studied by an increasing of a number of the basis functions N. This allows to claim that the obtained energy values have 26 significant digits for ground states. With the obtained results we calculate hyperfine splitting of the muonic helium atoms.     

相对论离子与氦二聚体碰撞电离的理论研究

基于对称程函近似,从理论角度研究了相对论离子与氦二聚体碰撞双电离的直接碎裂通道：由入射离子与两个原子的作用造成的双电离。从不同的近似角度出发,建立了两个理论模型,第一个模型将氦二聚体的两个原子看做一个整体,而另外一个模型完全忽略了两个氦原子之间的相互作用。模型的数值计算结果表明,总截面与氦二聚体的空间取向有很强的依赖关系,当氦二聚体与入射离子束流平行时,总截面达到最大值,在垂直时为最小值。进一步研究发现,模型一的结果在氦二聚体核间距较小时更为合理,核间距较大时,模型二更为精确。     

Recent Experiments Involving Few-Nucleon Systems

Recent experimental results are presented for reactions involving A = 3 to A = 6 nuclear systems. The emphasis is on unique data obtained at new experimental facilities. It is shown that the inertial confinement fusion facilities OMEGA and NIF provide a largely unexpected opportunity for experimental few-body physics to both obtain data of unprecedented quality and extend previous measurements to energies not accessible in the past. Whenever possible, data are compared to state-of-the-art theoretical calculations.     

Quasi-Molecular Optical Transitions near Resonance Lines of Kr and Xe Atoms in Helium

Optics and Spectroscopy - The emission and absorption spectra of Kr and Xe atoms near the 1,3P1–1S0 resonance lines in an atmosphere of helium atoms under equilibrium conditions have been...     

非全裸氟离子与氦原子碰撞中的转移电离过程

采用位置灵敏探测和散射离子 反冲离子飞行时间测量技术 ,测量了强相互作用区氟离子与氦原子碰撞中的转移电离截面与单电子俘获截面之比 .实验发现 ,该比值随作用强度的增加而减小 .在本工作能区 ,转移电离现象可视作一个电子被俘获、另一个电子被电离的两步过程 ;He原子二重电离的主要机制为两步机制. The cross-section ratios of the transfer ionization to the single electron capture of helium induced by fluorine ions in the strong-interaction region were measured by means of the position-sensitive-detecting and the time-of -flight (TOF) technologies. Is is found that the cross section ratios decrease with the increasing of the interaction-strength κ in this work. In the energy range of this work, the transfer ionization can be considered as a two-step process that one electron is captured by projectile...     

Ionization of Hydrogen and Helium Atoms in Collisions with Relativistic Structural Heavy Ions

Based on the eikonal approximation, cross sections for single and double ionization of hydrogen and helium atoms in collisions with structural multiply charged heavy ions moving with relativistic velocities are calculated. In the present paper, the structural ions are taken to mean the ions with partially filled electronic shells. It is demonstrated that a consideration of the ion charge extension may noticeably change the corresponding cross sections compared to the cross sections for ionization by point ions having the same charges and energies.     

化学体系随机共振现象的理论研究

化学体系中随机共振现象的特性、机理、本质和应用的研究是非常重要的前沿课题。综述中国科学技术大学非线性化学实验室,在化学体系随机共振现象的理论研究中,所取得的主要成果,并阐述化学体系随机共振现象研究中所提出来的若干重要问题：非均相化学体系中随机共振;化学体系中内信号随机共振;化学体系中多重随机共振;化学体系中随机共振的调制;化学体系中色噪声作用下的随机共振;化学体系中时空随机共振;耦合化学体系中随机     

Partial Wave Cross Sections for Collisions between Helium Atoms and Hydrogen Halide Molecules

The close-coupling method is utilized to calculate partial cross sections for elastic and inelastic scattering of He atoms with HX （X=F, Cl, Br） molecule based on the CCSD （T） potential energy surfaces obtained in the previous research. The calculation is performed at the incident energy of 200 me V. The rationality of our results has been confirmed by comparison with the available theoretical results. The tendency of the elastic and inelastic rotational excitation partial wave cross sections varying with the reduced mass of the three systems is obtained.     

Ranges of Hydrogen,Deuterium, and Helium Atoms in Amorphous Silicon and Tungsten

Technical Physics - We have obtained the range distributions for H, D, and He atoms within an energy range of 0.1–100 keV in amorphous W and Si for the normal incidence of bombarding...     

亚稳态氦共振荧光激光雷达系统方案比较分析

对脉冲光和连续光两种激光雷达系统进行了改进,在原有激光雷达系统的基础上进一步细化设计参数,并结合系统本身限制选择更合适的设备.对两种激光雷达系统回波信号进行模拟计算,并就信噪比和实现难度等方面进行了对比,结果表明,脉冲光激光雷达更合适探测热层和外逸层亚稳态氦密度.     

Na原子及类Na离子Fe15+价壳层光电离过程的理论研究

采用相对论多组态Dirac-Fock理论,计算了Na原子及类Na离子Fe15++基态的光电离截面.对Na原子,考虑相对论效应与弛豫效应,本文计算结果与前人计算结果和实验测量结果一致性较好.对Fe15+离子的最外价电子,相对论效应对其光电离过程产生主要影响,而轨道弛豫效应则可忽略不计;对中性Na原子则情况完全不同:轨道弛豫效应的影响非常显著,但其光电离截面对相对论效应仅有非常微弱的依赖.     

卟啉内氢迁移反应氟取代基效应的理论研究

采用B3LYP/6-31G**的方法在Gaussian03程序下对卟吩(PH2)、m-四氟卟啉(m-TFPH2)、β-八氟卟啉(β-OFPH2)和m-四氟,β-八氟卟啉(12FPH2)的结构进行几何优化,并进行振动分析.计算并讨论了PH2、m-TFPH2、β-OFPH2和12FPH2在内氢迁移反应中的反应物、产物、中间体、过渡态及二级鞍点的结构与能量.通过对结构和能量的比较,发现各物质内氢迁移反应均以异步历程进行,可见取代基对卟啉内氢迁移反应的历程选择没有影响.但取代基会影响同步历程和异步历程之间的速率差异.另外,氟取代基使得内氢迁移反应的异步历程的正负反应速率有所减小,起决定性作用的是取代基的电子效应,这些与化学直观也是相一致的.     

Influence of BBR-Induced Level Mixing Effect on Cosmological Recombination of Hydrogen and Singly Ionized Helium Atoms

An effect of atomic line broadening induced by the blackbody radiation (BBR) is investigated. Two physically different processes that affect the line broadening are compared within the framework of quantum electrodynamics (QED): the stimulated Raman scattering and BBR-induced level mixing. It is shown that the mixing effect gives the most significant contribution to the line broadening. According to our analysis, it is possible to distinguish both effects in the laboratory experiments. The impact of BBR-induced level mixing on the recombination history of primordial hydrogen and singly ionized helium atoms is discussed.     

Metastable States in Antiprotonic Helium Atoms: An Island of Stability in a Sea of Continuum

 In this contribution we consider a phenomenon of metastable states in antiprotonic helium atoms, precise spectroscopy of these states and a present-day study of the electromagnetic properties of antiprotons. Received October 16, 2001; accepted for publication November 13, 2001