HD2+通过超薄碳膜的"尾流"效应

快分子离子穿过固体时会产生库仑爆炸(Coulomb Explosion),尾流效应是库仑爆炸中的一个显著特性.HD2 的爆炸能谱在实测中发现了一些引人注目的特性:1)H 的尾流效应特别显著;2)H 的能谱结构非常类似HeH 中H 的能谱;3)尾流效应在D 的能谱中体现得很弱.这些特性对分析了解HD2 的结构和物理化学性质有很大的帮助.本文依照“尾流”效应(Wake Effect)的等离子体模型,将爆炸中两个D 产物的尾流场近似认为一个He 的尾流场,模拟计算了1.4977 MeV HD2在100 nm碳膜中分解后0°方向的能谱形式.给出了相同条件下的实验结果,得到了非常接近的结果,并将两者作了比较和分析.文中同时给出了D 的实验能谱,对D 的尾流效应相对较弱作了分析,指出对不同产物分辨的差异、产物的非直线运动等是造成D 尾流效应弱的原因.     

Electrical Conductivity of Nonideal Plasma

The electrical conductivity of fully ionized moderately nonideal plasmas with coulomb interaction parameters 0.1 < ? ? 1 where ? = Ze2n1/3/KT is the ratio of coulomb and thermal energies is calculated for displaced Maxwell and Fermi electron distributions, respectively. The electrons are scattered by an effective coulomb potential ?(r) = Zer-1 exp (-r/?) which considers binary (0 < r < ?) and many-body (? < r < ?) interactions. The shielding distance is given by ? = ?(4?n/3Z)-1/3 with ? = ?0?-N ~ 1 for classical plasmas and ? = ?(4?n/3Z)-1/3 with ? = ?0?-N?-M ~ 1 for quantum plasmas, where ? = Ze2n1/3/h2 m-1n2/3 is the ratio of coulomb interaction and quantum potential energies of the electrons. It is shown that the resulting conductivity formulas are applicable to densities up to four orders of magnitude higher than those of the ideal conductivity theory, which breaks down at higher densities because the Debye radius loses its physical meaning as a shielding length and upper impact parameter.     

Debye screening

The existence and exponential clustering of correlation functions for a classical coulomb system at low density or high temperature are proven using methods from constructive quantum field theory, the sine gordon transformation and the Glimm, Jaffe, Spencer expansion about mean field theory. This is a vindication of a belief of long standing among physicists, known as Debye screening. That is, because of special properties of the coulomb potential, the configurations of significant probability are those in which the long range parts ofr ^–1 are mostly cancelled, leaving an effective exponentially decaying potential acting between charge clouds. This paper generalizes a previous paper of one of the authors in which these results were obtained for a special lattice system. The present treatment covers the continuous mechanics situation, with essentially arbitrary short range forces and charge species. Charge symmetry is not assumed.Supported in part by N.S.F. Grant PHY 77-02187 and MCS 79-02490     

Coulomb forces in the three-body problem with application to direct nuclear reactions

Faddeev equations are considered in the case of three charged particles interacting with both separable nuclear two-body interactions and also including Coulomb forces. Modified Faddeev equations with Coulomb Green's functions are introduced. The three-body amplitudes are given into pure Coulomb and distorted-Coulomb amplitudes. Introducing a decomposition in the angular momentum states, a set of three-body integral equations is obtained. The effect of pure coulomb amplitudes is studied in direct nuclear reactions and found to give a large contribution to the cross sections. The three-body integral equations obtained are applied for direct nuclear reactions. The angular distributions for¹²C(⁶Li,d)¹⁶O,¹⁶O(⁶Li,d)²⁰Ne, and¹²C(⁶Li,α)¹⁴N transfer reactions are calculated as well as for the⁶Li elastic scattering on¹²C. From the good agreement between the theoretically calculated and experimental data, better spectroscopic factors are extracted. The effect of including Coulomb forces in the three-body problem is found to improve the results by about 16.26%.     

Structure and diffusion in mixtures of ionic liquids

The properties of ionic mixtures of LiBr-KBr are investigated on the basis of molecular dynamics calculations, using the Tosi-Fumi pair-potentials. The determination of the excess internal energy of mixing indicates the predominant negative contribution of the coulomb energy. The position of the first peak of the anion-cation radial distribution function depends strongly on the size of the ions and its height is much influenced by the strength of the coulomb forces. It is shown that the equivalent coordination numbers vary from about 4 for the Li-Br pair to 6 for the K-Br pair. These numbers do not change very much when the composition is varied.

The ionic dynamics is analysed through the brownian-like formalism which gives a useful connection between the structure and the particle motion. Two mechanisms are involved in the diffusion process: an oscillation of the particle in the force field of the neighbouring particles and a collective mode of motion which has a longer relaxation time. The strong anion-cation correlation, which mainly affects the smallest cation, dominates when the charge ordering (quasi-lattice structure) vanishes.     

Pair production from hot plasma in the presence of a strong magnetic field

Acta physica Academiae Scientiarum Hungaricae - Radiation loss due to pair production by an intense electromagnetic wave is calculated. The calculations were made in the coulomb field of the ions...     

Variational calculation of some S-states of Coulomb three-body systems

A generalized Hylleraas-type basis set with three nonlinear parameters is proposed to study three-body systems interacting via coulomb forces within the framework of non-relativistic quantum mechanics. This basis set improves the rate of convergence with respect to previous ones, specially for non-symmetric systems and excited states of two electron atoms. Accurate binding energies and other properties for S-states of helium-like ions, muonic molecules and the positronium negative ion are reported. Received 21 July 2000 and Received in final form 4 October 2000     

用电光采样法测量相对论电子束团长度

 介绍了电光采样法测量电子束束团长度的实验原理和装置,理论分析并模拟计算了被测电子束团库仑场分布、ZnTe晶体的电光效应与束团电场的关系,并利用琼斯矩阵法分析了探测光通过电光晶体时在束团电场作用下的偏振变化、测量信号与束团长度的关系等。分析表明：测量中应使束团库仑场垂直于ZnTe的［001］方向,探测光偏振方向与ZnTe晶体y″轴成45°或者135°夹角,1/4波片快轴与探测光偏振方向夹角应取45°,这时平衡探测器输出信号与束团库仑场Eb成正比。1/4波片的作用是将电光晶体的工作点从非线性段移到线性段,平衡探测的作用是简化信号与Eb的关系,并提高信噪比。为实际测量应用提供参考。     

共轭聚合物中库仑作用对定域激发的影响

利用紧束缚哈密顿量计算共轭聚合物(conjugated polymers)中库仑作用对于电中性的定域激发态的影响。对于反式(CH)_x计算了激子谱,重新计算了光吸收系数,对边缘部分进行了修正,所得到的结果与实验符合。 关键词：     

Comparison of structure factors and pair correlation functions obtained using coulomb attractive potential and screened coulomb potential for the suspended macroions

The structure factors and pair correlation functions have been calculated for the macroions suspended in water using coulomb attractive potential (CAP) and the results have been compared well with the results obtained from the RMSA and MMSA using screened coulomb potential (SCP). Differences among the values of compressibility in the limit of zero momentum transfer, excess energy per macroion and coordination number for both the potentials have been reported. Liquid like ordering of the FCC type has been obtained using both CAP as well as SCP potentials between suspended macroions.     

碰撞电离产生Au L3空穴态定向行为的研究

采用一种简单的实验方法测定低能区几种离子与Ａｕ碰撞产生Ａｕ的Ｌ₃空穴态的定向度，及定向度的入射离子能量相关性；同时在平面波玻恩近似理论基础上加上库仑偏转效应的校正进行了理论计算，改善了实验点与平面波玻恩近似理论计算的符合程度，讨论了有关空穴态定向行为。 关键词：     

A Direct Calculation of First-Order Wave Function of Helium

We develop a simple analytic calculation for the first order wave function of helium in a model in which nuclear charge screening is caused by repulsive coulomb interaction. The perturbation term, first-order correlation energy, and first-order wave function are divided into two components, one componentassociated with the repulsive coulomb interaction and the other proportional to magnetic shielding. The resulting first-order wave functions are applied to calculate second-order energies within the model. We find that the second-order energies are independent of the nuclear charge screening constant in the unperturbed Hamiltonian with a central coulomb potential.     

The absolute positions of calculated energy bands

The absolute positions of calculated crystalline energy bands depend upon the choice of charge cluster used to generate the total crystalline charge for the coulomb potential calculation. The coulomb potential (and hence the bands) will be shifted from the Ewald limit by 2π times the trace of the second moment tensor of the charge cluster divided by three times the volume of the unit cell. Energy bands obtained from different calculational models can thus all be corrected to the same Ewald limit. Energy bands can also be aligned more realistically with those in a finite crystal by calculating the shift in the bands from the Ewald limit due to a free atom or ion surface charge density.     

Electrical Conductivity of Nonideal Quasi-Metallic Plasmas

Electrical conductivity formulas are derived from first principles for fully ionized nonideal plasmas. The theory is applicable to an electron-ion system with a 1) Maxwell electron distribution with an arbitrary interaction parameter ? = Ze2n1/3/KT (ratio of the mean coulomb interaction and thermal energies) and 2) Fermi electron distribution with an interaction parameter ? = Ze2n1/3h?2m-1 n2/3 (ratio of the coulomb interaction and Fermi energies). The momentum relaxation time of the electrons in the plasma is calculated based on plane electron wave functions interacting with the continuum oscillations (plasma waves) through a shielded coulomb potential Us(r) = esee exp (-r/?s)/r, which takes into account both electron-ion interactions (s = i) and electron-electron interactions (s = e). It is shown that the resulting conductivity formulas are applicable to higher densities, for which the ideal plasma conductivity theory breaks down because the Debye radius loses its physical meaning as a shielding length and upper impact parameter. The conductivity obtained for classical plasma is of the form ?c = ?c*(KT)3/2/m1/2e2 and agrees with the ideal plasma conductivity formula with respect to the temperature and density dependence for ?/Z ? 0, but its magnitude is significantly reduced as ?/Z increases. For quantum plasmas, the conductivity obtained is of the form ?Q = ?Q*h3n/m2Ze2, which shows that the degenerate plasma behaves like a low-temperature metal.     

准一维体系的电子关联函数

对于具有库仑相互作用的准一维电子体系,本文根据电子气的集体振荡行为给出了该体系的多体波函数,并由此求出了准一维体系的电子关联函数g(|z₁₂|)。 关键词：     

Electromagnetic form factors of3He and3H

The electric and magnetic form factors of³He and³H are calculated with 3-nucleon wave functions obtained from the solution of Schrödinger equation with separable potentials of two different shapes which have already been employed in the coulomb energy calculation. The effect of important meson exchange corrections is evaluated and their dependence on the wave function studied. The form factors can depend rather sensitively on the nucleon form factors as well, and this dependence is studied by using two different parametrisations for the latter.     

Quark potentials for mesons in the Klein-Gordon equation

Two relativistic potential models are applied to describe meson spectroscopy in a unified way, encompassing both light and heavy quark systems. A combination of linear and coulomb potentials has been investigated for Klein-Gordon equation using the WKB approximation. A power-like phenomenological potential model has also been studied in the Klein-Gordon framework. Meson masses calculated for both the potentials give a good agreement with the corresponding experimental values.     

On the validity of the triple-dipole interaction as a representation of non-additive intermolecular forces

A complete partial wave analysis of the non-expanded non-additive coulomb interaction energy for three non-degenerate S-state atoms is given through third-order in the interatomic potential energy function. Pseudo state techniques are used to evaluate various partial wave components of the non-expanded second and third-order non-additive interaction energies for various isosceles triangular configurations of three interacting ground-state hydrogen atoms. These second and third-order non-expanded coulomb results are used, in conjunction with Heitler-London results for the first-order non-additive energies for the quartet spin state of the H(1s)-H(1s)-H(1s) interaction, to discuss the relative importance of various parts of the non-additive energy as a function of the geometrical configuration of the atoms, and the validity of both the non-expanded triple-dipole energy and the expanded Axilrod-Teller-Muto triple-dipole result as a representation of non-additive coulomb energies. For example, in the non-bonded interaction of three S-state atoms it appears that representing the non-additive energy by the non-additive coulomb energy is not reliable until the interatomic separations are somewhat larger than R*, the interatomic distance associated with the van der Waals minimum in the corresponding non-bonded dimer interaction. Further, the use of the triple-dipole interaction energy, with or without charge overlap corrections, to represent the non-additive coulomb energy is of doubtful validity until the interatomic separations are considerably greater than R*.     

串型耦合双量子点之间库仑作用对其近藤共振的影响

从理论上研究了串型耦合双量子点之间库仑作用对其近藤共振的影响. 采用非平衡态格林函数和奴役玻色子平均场近似方法求解了系统的哈密顿量; 计算了系统电子的态密度、透射率、占居数和近藤温度随双量子点之间库仑作用能的变化, 同时也计算了电极处于极化时双量子点之间库仑作用能对系统电子态密度的影响. 结果表明,双量子点之间库仑作用能够极大地影响系统的基态物理性质. 同时还对相关的物理问题进行了讨论.     

Identification of the dynamic characteristics of a structure with coulomb friction

The effect of coulomb friction on the Kennedy and Pancu vector plot of a single degree-of-freedom system is analyzed by using the method of harmonic balance. It is shown that the resulting diagram no longer conforms to a locus of a circle in the resonant region, which restricts the usual methods of analysis. A technique, based upon the in-phase and quadrature power dissipated when exciting a normal mode, is presented which allows the magnitude of the non-linear friction force and the hysteretic damping constant to be evaluated. The technique is also applied to systems having several degrees-of-freedom and it shows that it is possible to identify the characteristics of a single non-linear coulomb device situated within a structure, but in the case of more than one device, the technique has some restrictions. The theoretical results are compared with experimental data from a structure containing a non-linear coulomb device.