氢负离子在电介质球面附近的光剥离研究

利用镜像法结合半经典闭合轨道理论,对氢负离子在电介质球面附近的光剥离进行了研究.首先利用镜像法分析了剥离电子在电介质球内的镜像电荷分布情况,然后给出了体系的哈密顿量.通过求解哈密顿正则方程,找到了剥离电子在电介质球面附近运动时的闭合轨道.借助于半经典闭合轨道理论,推导出了体系的光剥离截面,并且对光剥离截面进行了计算和分析.计算结果表明,氢负离子在电介质球面附近的光剥离截面不仅与入射光子的能量有关,而且还与电介质球面的介电常数有关.对于给定的电介质球面,随着入射光子的能量增加,光剥离截面的振荡振幅减小、振荡频率增加.当入射光子的能量增加到某一临界值时,光剥离截面的振荡结构消失.除此之外,随着电介质球面介电常数的增大,光剥离截面的振荡结构变得更加复杂.当电介质常数增大到无穷大时,体系的光剥离截面和氢负离子在金属球面附近的光剥离截面一致.因此,可以通过改变入射光子的能量及电介质球面的介电常数对氢负离子在电介质球面附近的光剥离截面进行调控研究.研究结果对负离子体系在电介质球面附近的光剥离的实验研究可以提供一定的理论指导和参考价值.     

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.     

Photodetachment of H- near an elastic surface in a magnetic field

This paper investigates the photodetachment of the negative hydrogen ion H near an elastic wall in a magnetic field.The magnetic field confines the perpendicular motion of the electron,which results in a real three-dimensional well for the detached electron.The analytical formulas for the cross section of the photodetachment in the threedimensional quantum well are derived based on both the quantum approach and closed-orbit theory.The magnetic field and the elastic surface lead to two completely different modulations to the cross section of the photodetachment.The oscillation amplitude depends on the strength of the magnetic field,the ion-wall distance and the photon polarization as well.Specially,for the circularly polarized photon-induced photodetachment,the cross sections display a suppressed(E E th) 1/2 threshold law with energy E in the vicinity above Landau energy E th,contrasting with the(E E th) 1/2 threshold law in the presence of only the magnetic field.The semiclassical calculation fits the quantum result quite well,although there are still small deviations.The difference is attributed to the failure of semiclassical mechanics.     

量子计算正三角形腔内的氢负离子光剥离截面

用传统量子力学方法研究了横截面为正三角形的腔内氢负离子光剥离, 得到了光剥离截面随能量变化的解析表达公式. 该公式还给出了剥离截面的阈值行为. 进一步研究发现, 当氢负离子处于正三角形一角附近时, 用量子力学方法得到的结果与氢负离子处于60°角域内时使用闭合轨道理论得到的结果一致.     

The influence of electric field on the photodetachment of H- near a metal surface

The influence of electric field on the photodetachment of H-near a metal surface is investigated based on the closed-orbit theory.It is found that the photodetachment of H-near a metal surface is not only related to the electric field strength but also to the electric field direction.If the electric field is along the +z axis,it can strengthen the oscillation in the photodetachment cross section.However,if the electric field is along the -z axis,since the direction of electric field force is opposite to that of static-image force caused by the metal surface,the situation becomes much more complicated.When the electric field is very weak,its influence can be neglected.The photodetachment cross section is nearly the same as that when a single metal surface exists.When the electric field strength is strong enough,the electric field force is able to counteract the metallic attraction,therefore no closed orbit is formed.If the electric field continues to increase until its influence becomes dominant,the photodetachment cross section approaches the case of the photodetachment of H- in an electric field.Our results may be useful for guiding future experimental studies on the photodetachment of negative ions near surfaces.     

氢负离子在变形球面附近的光剥离

利用理论模型成像方法, 对氢负离子在变形球面附近的光剥离进行了研究. 首先, 推导出了光剥离电子通量的计算公式, 然后对电子通量分布和光剥离截面进行了计算.结果表明: 平面效应只在一定范围内对氢负离子的光剥离过程产生影响. 在距离z轴比较近的区域, 球面效应起主要作用, 电子通量分布和光剥离截面与只有球面存在的情况一致, 此时平面效应可以忽略; 距离z轴较远的区域, 平面效应和球面效应共同起作用, 此时变形球面对光剥离过程会产生比较大的影响. 当球面半径和氢负离子到球面之间的距离给定, 随着入射光子的能量增大, 光剥离电子通量的振幅先增大后减小, 然后又慢慢增大, 振荡频率增大.当固定球面与氢负离子之间的距离, 随着球面半径的增大, 光剥离电子的通量趋向于只存在球面的情况.因此, 可以通过改变入射光子能量和球面的半径对氢负离子的光剥离进行调控. 本文的结果对于研究负离子体系在曲面附近的光剥离及光剥离 显微问题的实验研究具有一定的参考价值. 关键词： 理论模型成像方法 光剥离电子通量 光剥离截面 变形球面     

激光脉冲对氢负离子在金属面附近光剥离的影响

利用闭合轨道理论和金属面附近氢负离子的双脉冲光剥离截面的计算公式,计算了氢负离子在金属面附近激光脉冲作用下的光剥离截面.计算结果表明:如果脉冲宽度远大于闭合轨道的回归周期时,它对光剥离截面的影响很小;当脉冲宽度小于闭合轨道的周期或者可以和闭合轨道的周期相比较时,光剥离截面的振荡幅度大大地减弱.光剥离截面除了与脉冲宽度有关外,还与双脉冲之间的时间延迟、相位差有关.对于某些相位差, 双脉冲光剥离截面的取值增大; 而对于另外一些相位差, 光剥离截面的取值减小.因此,可以利用脉冲激光来控制氢负离子在表面附近光剥离 关键词： 激光脉冲 光剥离截面 金属面 闭合轨道理论     

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     

H-在金属面附近光剥离的波包动力学研究

利用波包演化和自关联函数方法对H^-在金属面附近光剥离的波包动力学进行了研究.结果表明,金属面附近光剥离电子的波包演化和回归结构与H^-到金属面的距离、激光脉冲的脉冲宽度和初始动量都有一定的关系.因此,可以通过改变离子表面距离和激光脉冲的参数对光剥离电子的动力学性质进行调控研究.除此之外,光剥离电子的镜像态寿命对波包的演化和自关联函数也会产生一定的影响:考虑镜像态寿命的影响时,随着时间的演化,波包概率密度的振幅逐渐减小,波包整体上有明显的衰减,寿命对波包演化过程中的干涉有削弱的作用;通过对电子波包的自关联函数研究,发现无限长寿命的电子波包有很好的量子回归现象,而当考虑寿命因素后光剥离电子波包随着时间的演化会发生周期性的坍塌和扩散,经过一段时间后,该回归现象消失.本文的理论研究可以为表面附近电子波包动力学的实验研究提供一定的参考价值. 关键词： 波包 演化和回归 自关联函数 金属面     

氢负离子在均匀电场和金属面附近的光剥离研究

利用闭合轨道理论,计算了氢负离子在均匀电场和金属面附近的光剥离截面.结果表明,在均匀电场的基础上加上金属面之后,在电离阈附近氢负离子的光剥离截面发生了很大的变化,和仅有均匀电场存在时的光剥离截面相比,截面的振荡幅度增大,振荡频率减小.并且在电场强度相同时,随着金属面与氢负离子距离的不断增大,光剥离截面振荡的幅度不断减小,振荡的频率不断增大,当金属面和氢负离子的距离增大到一定值时,金属面的影响消失,氢负离子的光剥离截面趋近于只有电场存在时的情况.这一结果对于研究负离子体系在界面附近的光剥离问题具有一定的参考价值.     

A semi-coherent interface with nanoledges intersecting the free surface of an elastic half-space

Abstract

The elastic field generated by a semi-coherent interface formed by a succession of parallel terraces and nanoledges is investigated when the interface intersects the free surface of an isotropic half-space medium. The method uses the combination of semi-infinite Somigliana dislocations placed on each terrace and semi-infinite translation (or Volterra) dislocations placed at one or two corners of the nanoledges. Numerical examples depict the deformation fields nearby emerging regions of two semi-coherent interfaces; one is flat, while the other includes nanoledges.     

氢负离子在磁场和电介质表面附近光剥离的研究

利用闭合轨道理论, 研究了变化的磁场和不同电介质表面对氢负离子光剥离截面的影响, 并推导出了该体系下的光剥离截面公式. 结果发现, 氢负离子的光剥离截面不仅与磁场的强度有关, 而且还与电介质常数有关. 当氢负离子到电介质表面的距离和电介质常数一定时, 体系的光剥离截面中的振荡随磁场的变化而明显变化. 随着磁场强度的 增大, 体系的闭合轨道数目增多, 光剥离截面的振荡越来越复杂. 当氢负离子到电介质表面的距离和磁场强度一定时, 电介质常数的变化对光剥离截面的影响也很重要, 随着电介质常数的增大, 体系的闭合轨道数目增多, 光剥离截面的振荡也变得越来越复杂. 因此, 可以通过改变磁场强度和电解质常数来调整负离子的光剥离截面. 此结果 对于研究负离子体系在表面附近和外场中的光剥离问题具有一定的参考价值.     

The closed-orbit and the photoabsorption spectra of the Rydberg hydrogen atom between two parallel metallic surfaces

Using the closed orbit theory, we study the classical motion and calculate the photoabsorption spectra of Rydberg hydrogen atom between two parallel metallic surfaces. The results show that the metallic surfaces have a significant effect on the photoabsorption process. When the distances between the hydrogen atom and the two metallic surfaces are close to a critical value d_c, the number of the closed orbits is the greatest. When the distance larger or smaller than d_c, the number of the closed orbits decreases and the absorption spectra are shown to exhibit a damping oscillation. This work is an interesting new application of closed-orbit theory and is of potential experimental interest.     

Photodetachment of negative ion in a gradient electric field near a metal surface

Based on closed-orbit theory, the photodetachment of H in a gradient electric field near a metal surface is studied. It is demonstrated that the gradient electric field has a significant influence on the photodetachment of negative ions near a metal surface. With the increase of the gradient of the electric field, the oscillation in the photodetachment cross section becomes strengthened. Besides, in contrast to the photodetachment of H near a metal surface in a uniform electric field, the oscillating amplitude and the oscillating region in the cross section of a gradient electric field also become enlarged. Therefore, we can use the gradient electric field to control the photodetachment of negative ions near a metal surface. We hope that our results will be useful for understanding the photodetachment of negative ions in the vicinity of surfaces, cavities, and ion traps.     

氢负离子在微腔中的光剥离研究

利用闭合轨道理论,研究了氢负离子在金属面和弹性界面组成的微腔中的光剥离截面.结果表明,微腔的上下表面对氢负离子的光剥离截面产生很大影响.若固定金属面与氢负离子之间的距离不变,当弹性界面与氢负离子之间的距离很大时,弹性界面对氢负离子光剥离截面的影响很小,光剥离截面的振荡幅度和振荡频率与只有金属面时的情况类似.随着弹性界面和氢负离子之间距离的不断减小,光剥离截面的振荡幅度增大,振荡频率减小.若保持氢负离子和弹性界面之间的距离不变,随着金属面和氢负离子之间距离d₀的不断增大, 关键词： 光剥离截面 闭合轨道理论 微腔     

Photo-detachment cross section of H- near two parallel interfaces

The photo-detachment cross section of H^- near two parallel elastic interfaces is derived and calculated by using the closed orbit theory. The photo-detachment cross section of H^- near two interfaces is shown to exhibit multi-periodic oscillations when the distance between the H^- and the interface is varied. Each peak in the Fourier transformed photo-detachment cross section corresponds to the length of a closed orbit, which is quite similar to the case of atomic spontaneous emissions in a dielectric slab. This study provides a new understanding of the photo=detachment process of H^- in the presence of interfaces.     

Quantum calculations for photodetachment cross sections of H-in an inhomogeneous electric field

We calculate the photodetachment cross sections of H in a gradient electric field based on traditional quantum approach. The system provides a rare example that the formulas for the cross sections can be explicitly derived by both the quantum approach and closed-orbit theory. The quantum results are compared with those of the closed-orbit theory. The correct phase values in the closed-orbit theory are essential and necessary to produce accurate cross sections. Our quantum results remove some previous ambiguities in assigning the phase values in the closed-orbit theory (G. C. Yang and M. L. Du 2007 Phys. Rev. A 75 029904E).     

氢负离子在少周期激光场中解离时的干涉效应

本文利用强场近似理论研究了氢负离子在少周期激光场中的解离过程. 在计算中采用了数值积分和鞍点近似两种计算方法并得到了一致的结果. 更为重要的是, 利用鞍点法对激光脉冲中不同时刻解离产生的电子波包之间的干涉效应进行了研究, 发现光电子动量谱的主要结构是电子波包间的周期间干涉和周期内干涉共同作用的结果, 并分析了周期内和周期间干涉效应对光电子能量谱的影响. 最后, 讨论了激光脉宽对周期内和周期间干涉效应的影响. 本文的工作对进一步了解负离子光解离过程中的量子干涉效应和利用光场对其进行调控方面的研究具有意义.     

The dynamical properties of Rydberg hydrogen atom near a metal surface

The dynamical properties of Rydberg hydrogen atom near a metal surface are presented by using the methods of phase space analysis and closed orbit theory. Transforming the coordinates of the Hamiltonian, we find that the phase space of the system is divided into vibrational and rotational region. Both the Poincaré surface of section and the closed orbit theory verify the same conclusion clearly. In this paper we choose the atomic principal quantum number asn=20. The dynamical character of the exited hydrogen atom depends sensitively on the atom-surface distanced. Whend is sufficiently large, the atom-surface potential can be expressed by the traditional van der Waals force and the system is integrable. Whend becomes smaller, there exists a critical valued _c. Ford>d _c, the system is near-integrable and the motion is regular. While chaotic motion appears ford<d _c, and the system tends to be non-integrable. The trajectories become unstable and the electron might be captured onto the metal surface.     

The dynamical properties of Rydberg hydrogen atom near a metal surface

In recent years much attention is focused on the dynamics of Rydberg atom in exter- nal fields. At the same time Rydberg atom near a metal surface plays an important role as a typical theoretical model and produces measurable experimental response[1]. As an interesting model it covers many dynamical effects: instantaneous van der Waals inter- action[2,3], Zeeman-Stark effects and diamagnetic effects in strong fields[4], and so on. Its classical motion is very complex. When the atom-surface i…