Electric flux distribution in photodetachment of heteronuclear diatomic molecular negative ion

The photodetachment of a hetero-nuclear diatomic molecular negative ion is studied by using a two-centre model. An analytic formula is presented for the electron flux distribution of a heteronuclear diatomic molecular negative ion. Taking HF^- as an example, we calculated the electron flux distributions of this ion for various detached electron energies. The results show that the electron flux distributions exhibit oscillatory structures, which are caused by the interference effect between the two nuclei. Besides, the laser light polarization also has a great influence on the electron flux distribution. The oscillation amplitude is the largest when the laser polarization is parallel to the z-axis; when the laser polarization is perpendicular to the z-axis, the oscillation almost vanishes. This study provides a new understanding of the photodetachment of a heteronuclear diatomic molecular negative ion.     

Interferences in Photodetachment of a Negative Molecular Ion Model

By employing a two-center model, the total and differential cross sections in the photodetachment of ＂a negative molecular ion＂ are studied theoreticedly and obtained for the case of light polarization paredlel to the molecular axis. We find that in contrast to the smooth behavior of the total cross section for perpendicular polarized light, the cross section for parallel polarized light shows an interesting oscillatory structure. The oscillations in the toted cross section may provide a method to determine the distance between the two centers. We explain the oscillation in the toted cross section as an interference effect using closed-orbit theory. We also cedculated the detached-electron flux distributions on a screen placed at a large distance from the negative molecular ion. The distributions display multiple-ring-like interference patterns. Such interference patterns are similar to those in the photodetachment microscopy experiments.     

Interferences in Photodetachment of a Negative Molecular Ion Model

By employing a two-center model, the total and differential cross sections in the photodetachment of ``a negative molecular ion" are studied theoretically and obtained for the case of light polarization parallel to the molecular axis. We find that in contrast to the smooth behavior of the total cross section for perpendicular polarized light, the cross section for parallel polarized light shows an interesting oscillatory structure. The oscillations in the total cross section may provide a method to determine the distance between the two centers. We explain the oscillation in the total cross section as an interference effect using closed-orbit theory. We also calculated the detached-electron flux distributions on a screen placed at a large distance from the negative molecular ion. The distributions display multiple-ring-like interference patterns. Such interference patterns are similar to those in the photodetachment microscopy experiments.     

Electron flux distributions in photodetachment of H<Superscript>-</Superscript> in parallel electric and magnetic fields

Photo-detached electrons of negative hydrogen ion in parallel electric and magnetic fields show quite complicated classical dynamical behavior, and a sequence of bifurcation and anti-bifurcation occurs. We investigate the effects of bifurcations on the flux distribution of photo-detached electrons by using position and momentum diagrams. Detached-electron flux distributions are calculated based on a uniform semi-classical theory. The flux distributions exhibit patterns with multiple rings. The bright rings correspond to special points in the diagrams. The flux distributions can be controlled by adjusting the magnetic field strength while fixing the electric field.     

Interferences in photo-detached electron spectra from a non-collinear tri-atomic anion

The electron flux oscillations in photo-detachment of a non-collinear tri-atomic anion have been studied by taking each atom of the system as a coherent source of detached-electron wave. These electron waves traversing along three different trajectories result in a quantum interference. An analytical expression of detached-electron flux is evaluated for various detached-electron energies and for different geometrical shapes of the system. The results show that the electron flux distributions exhibit molecular shape-induced oscillatory structures. These oscillations are explained using the semi- classical closed-orbit theory; the outgoing electron waves produced from one center are propagated in the vicinity of the sources at other centers. It is also observed that in a particular case our non-collinear tri-atomic system reduces to the collinear tri-atomic system recently published.     

电场不均匀性对外场中负离子光剥离的影响

用蒙特卡罗方法研究了不均匀外场中氢负离子的光剥离.模拟结果显示出电场的不均匀抑制了光剥离截面和相应调制函数的振荡.光剥离截面的高能部分比阅值附近部分对电场的不均匀性更为敏感.结後果对纯电场和平行电场与磁场两种情形均适用.     

氢负离子在磁场和金属面附近电子通量分布的研究

利用半经典开轨道理论, 研究了磁场和金属面附近氢负离子的剥离电子通量分布, 并揭示了电子通量分布中的振荡结构与经典轨道之间的关系.固定离子到金属面的距离, 研究了不同的磁场强度对电子通量分布的影响. 结果表明, 由于与电子通量分布相联系的剥离电子的经典轨迹增加, 随着磁场强度的增加, 通量分布变得复杂. 此外发现剥离电子的能量变化也会影响电子通量分布. 因此可以通过改变磁场强度大小和剥离电子的能量来调控剥离电子通量分布和干涉图样. 研究结果对于理解负离子在外场、表面附近的电子流通量和剥离电子干涉图样问题以及将来实验研究负离子的光剥离显微问题都可以提供一定的参考. 关键词： 开轨道理论 电子通量 金属面 磁场     

The influence of interface modifier on photodetachment of negative ions in an electric field near a metal surface

Based on closed-orbit theory,the influence of an interface modifier on the photodetachment of H- in an electric field near a metal surface is studied.It is demonstrated that the interface strengthens the oscillations in the photodetachment cross section.However,when the electric field environments are different,the strengthening oscillations are caused by different sources.When the electric field direction is upward,the interface enhances the oscillations by shortening the period and the action of the closed orbit.When the electric field direction is downward,the interface strengthens the oscillations either by extending the coherent energy range or by increasing the total number of the closed orbits.We hope that our results will be conducive to the understanding of the photodetachment process of negative ions near interfaces,cavities and ion traps.     

Electron Flux Distributions in the Photodetachment of H2- in an Electric Field

The electron flux distributions in the photdetachment of a negative hydrogen molecular ion in an electric field have been studied by using the two-center model and the dosed orbit theory. An analytic formula is presented for the electron flux of H2 in the presence of an electric field. The results show that the interference between the two orbits passing through the given spatial point leads to the oscillation in the electron flux distribution. Besides, the interference between the two centers of the H2^- is also very important. The comparison between the electron flux of H2^- in electric field with the result of H^- shows that at the equilibrium distance of two centers in the H2^-, the interference of the two nuclei on the detached electron＇s flux distribution is very strong, while at larger distance of the two centers, the interference effect of the two centers is decreased.     

静态偏振风成像干涉仪光传输特性和光通量改善

静态偏振风成像干涉仪利用偏振光束来获得干涉图, 光束在偏振元件中的传输特性成为分析研究的关键. Jones矩阵用于分析系统的光学传输特性和偏振态变化过程, 形式简洁,计算方便,容易得出光学元件对系统性能的影响.本文用Jones矩阵对静态偏振风成像干涉仪系统进行了描述, 推导出了适用于普遍情况的系统矩阵表达式,计算出核心偏振元件的偏振化方向和波片方位角对应于系统光通量和干涉调制度的关系,确定了系统中各偏振元件的最佳偏振化方向和波片的最佳方位角; 并通过视场展宽技术和提高四面角锥棱镜的透光率对光通量加以改善,利用光线追迹软件仿真, 对视场展宽前后的干涉强度作了对比,达到预期的效果.为静态偏振干涉成像光谱仪的设计、 研制和工程化提供重要理论和实践指导.     

Vibrational spectra obtained from high quality potential energy surfaces spanned by low level normal coordinates: application to CHFClI and CDFClI

The impact of approximate normal coordinates for spanning high level potential energy surfaces on vibrational frequencies is studied within the framework of vibrational SCF and configuration interaction calculations (VCI). The use of low level normal coordinates avoids expensive geometry optimizations and harmonic frequency calculations and thus allows for a significant reduction in CPU time. Benchmark calculations are provided for a set of molecules ranging from 5 to 7 atoms. An application to CHFClI and CDFClI shows that this approximation still allows for very accurate results. These molecules are of particular interest for studying parity violation effects.     

Photodetachment microscopy of a hydrogen negative ion in an electric field near a metal surface

According to the semi-classical theory, we study the photodetachment microscopy of H- in the electric field near a metal surface. During the photodetachment, the electron is photo-detached by a laser and the electron is drawn toward a position-sensitive detector. The electron flux distribution is measured as a function of position. Two classical paths lead the ion to any point in the classically allowed region on the detector, and waves traveling along these paths produce an interference pattern. If the metal surface perpendicular to the electric field is added, we find that the interference pattern is related not only to the electron energy and the electric-field strength, but also to the ion-surface distance. In addition, the laser polarization also has a great influence on the electron flux distribution. We present calculations predicting the interference pattern that may be seen in experiment. We hope that our study can provide a new understanding of the electron flux distribution of negative ions in an external field and surface, and can guide future experimental research on negative ion photo-detachment microscopy.     

Electron Magnetic Moment in Highly Charged Ions: The ARTEMIS Experiment

The magnetic moment (g‐factor) of the electron is a fundamental quantity in physics that can be measured with high accuracy by spectroscopy in Penning traps. Its value has been predicted by theory, both for the case of the free (unbound) electron and for the electron bound in a highly charged ion. Precision measurements of the electron magnetic moment yield a stringent test of these predictions and can in turn be used for a determination of fundamental constants such as the fine structure constant or the atomic mass of the electron. For the bound‐electron magnetic‐moment measurement, two complementary approaches exist, one via the so‐called “continuous Stern–Gerlach effect”, applied to ions with zero‐spin nuclei, and one a spectroscopic approach, applied to ions with nonzero nuclear spin. Here, the latter approach is detailed, and an overview of the experiment and its status is given.     

高离化态类氖离子的电子碰撞激发特性研究

利用基于多组态Dirac-Fock(MCDF)理论方法的原子结构和性质计算程序GRASP92和全相对论扭曲波电子碰撞激发计算程序REIE06,系统计算了类氖离子(Z=50—57)激发组态2s22p53l和2s2p63l(l=s,p,d)的能级结构和碰撞激发截面,总结了碰撞激发截面随入射电子能量的变化规律,讨论了实验中感兴趣的(2p1/23d3/2)1→2s22p61S0(标记为3C线)与(2p3/23d5/2)1→2s22p61S0(标记为3D线)跃迁线强度比值的沿等电子系列特性和强组态相互作用对高离化态类氖离子截面的影响.     

Macroscopic resonant tunneling in an rf-SQUID flux qubit under a single-cycle sinusoidal driving

We experimentally demonstrate the observation of macroscopic resonant tunneling(MRT) phenomenon of the macroscopic distinct flux states in a radio frequency superconducting quantum interference device(rf-SQUID) under a singlecycle sinusoidal driving.The population of the qubit exhibits interference patterns corresponding to resonant tunneling peaks between states in the adjacent potential wells.The dynamics of the qubit depends significantly on the amplitude,frequency,and initial phase of the driving signal.We do the numerical simulations considering the intra-well and interwell relaxation mechanism,which agree well with the experimental results.This approach provides an effective way to manipulate the qubit population by adjusting the parameters of the external driving field.     

CN(X )系统碰撞转动传能中的量子干涉效应

在之前的研究中,已经对ＣＮ碰撞诱导转动传能中由于分裂引起的量子干涉效应进行了研究．为了进一步研究,本文讨论了微分干涉角．在一级波恩近似下,考虑各项异性相互作用势,及影响干涉的各个因素．定量计算了微分干涉角,及其随参数、温度的变化趋势．     

Velocity imaging for the liquid-gas interface in the near field of an atomizing spray: proof of concept

We describe adaptation of ballistic imaging for the liquid core of an atomizing spray. To describe unambiguously the forces that act to break apart the liquid core in a spray, one must directly measure the force vectors themselves. It would be invaluable, therefore, to obtain velocity and acceleration data at the liquid-gas interface. We employ double-image ballistic imaging to extract velocity information through the application of image analysis algorithms. This method is shown to be effective for liquid phase droplet features within the resolution limit of the imaging system. In light of these results, it is clear that a three- or four-image implementation of this technique would allow the determination of acceleration, and by extension, information about the forces active in spray breakup.     

Ta及Nanbu库仑碰撞模型数值对比研究

深入研究库仑碰撞,对两种库仑碰撞模型-Ta模型与Nanbu模型在理论上进行了对比分析,详细阐述了两种模型中散射角大小的区别.在已有的采用Ta模型的全三维粒子模拟/蒙特长罗(PIC/MCC)算法基础上,采用Nanbu模型对电子间库仑碰撞计算模块重新进行了算法设计.分别应用Ta模型、Nanbu模型和无库仑碰撞的全三维PIC/MCC算法对国外热门负氢离子源JAEA 10A中的电子能量沉积进行了模拟分析.模拟结果与实验结果的对比分析发现:1)库仑碰撞使电子能量分布更接近于麦克斯韦分布;2)相对于传统的Ta模型,Nanbu模型的散射角考虑了多体碰撞的累加效果从而具有更高的期望值,按其模拟得到的电子温度具有更高的精度.这些为国内外学者设计相关算法指明了方向.     

从二维到三维的场致电子发射:电动力学与量子力学相结合的一个例子

讨论电场使电子从纳米厚度的金属片经过量子隧穿进入真空的过程.忽略金属片的厚度,通过共形变换,使得真空电势和电子波函数满足简单的边界条件,从而得到严格的电势分布和近似的电子波函数解,给出发射电流密度空间分布的表达式.