共查询到19条相似文献,搜索用时 125 毫秒
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《中国光学》2019,(6)
采用电子波包干涉方法研究了长程库仑势以及再散射电子对氢原子在少周期强激光场中阈上电离的影响。首先,利用强场近似及Coulomb-Volkov近似结合时间窗函数,模拟了氢原子在波长为800 nm且脉宽为5 fs的线性极化激光场中单电离的周期内干涉及周期间干涉图像,发现在长程库仑势作用下周期内干涉及周期间干涉共同作用形成了二维动量谱中的部分扇形结构条纹,其余部分扇形条纹的形成与再散射电子有关。然后,通过数值求解含时薛定谔方程计算了深度隧穿电离机制下氢原子的二维动量谱,在二维动量谱中出现了明显的径向条纹。研究结果表明,该径向条纹的产生与长程库仑势无关,是再散射电子波包干涉形成的。 相似文献
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利用微扰理论,研究一维区域运动的自由电子,在受到弱周期势场的作用,给出在这种周期势场中的一维电子能谱,并与自由电子的能谱作比较。 相似文献
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在最弱受约束电子势模型理论中,电子被分成最弱受约束电子和非最弱受约束电子,而假定最弱受约束电子在核和非最弱受约束电子形成的势场中运动,这样许多多电子体系的问题可以简化成最弱受约束电子的单电子问题来解决.最弱受约束电子势模型理论已经被成功地应用于跃迁几率,振子强度和原子能级的计算.应用一组方程计算了Si III的离子自旋允许跃迁的跃迁几率,计算结果与标准值比较是相当令人满意的,误差均在15%以下.而且表明最弱受约束电子势模型理论可以非常简便并准确地应用于计算高激发态间的跃迁几率. 相似文献
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晶体电子在外场作用下的Bloch振荡和散射对电流的影响 总被引:1,自引:0,他引:1
通过对晶体周期势场中电子在直流外场作用下的Bioch振荡的分析,指出晶体在外场作用下的电流是由于电子受到散射的结果;没有散射作用,电子在外场作用下的运动为Bloch振荡,不产生电流。 相似文献
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通过引入变量,周期场中内部时间导数Ornstein-Uhlenbeck噪声驱动的布朗运动可用高维Fokker-Planck方程来描述. 上述系统不能直接应用通常的小参数展开和势谷中心展开近似求解. 用一种变通的小参数展开方法近似求解了系统的Fokker-Planck方程,结果适用于小势垒高度、中等关联时间和较大的相空间区域,近似解析解可获得系统的改进.
关键词:
Fokker-Planck方程
周期势
时间导数Ornstein-Uhlenbeck噪声
小参数展开 相似文献
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文中推导了一维周期耗散媒质中电磁波模式特征值方程,证明其解分类为一系列的"导带"和"禁带";用实数Re(Kz2)代替复特征值Kz标识模式,可清晰地显示出带结构,便于模式的分类和比较。文中用数值方法给出了几组参数下横电波、横磁波模最低两个带的图示,并与周期势场中的电子能带作了对比。 相似文献
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在非Born-Oppenheimer近似下,通过求解含时薛定谔方程的方法,对氢分子离子在不均匀场中高次谐波的产生进行了理论研究.计算结果显示,同均匀场相比,电离的电子在不均匀场中加速会获得更多的能量,从而更有利于得到宽频谱.此外,通过优化不均匀场中的空间不均匀度,长量子路径被明显的抑制,最终通过叠加110阶到150阶谐波,获得一个60as的孤立阿秒脉冲.同时,通过库仑势和激光场的相互作用势以及时频分布图解释了其中的物理机制. 相似文献
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对捕限在三维轴对称谐振势阱叠加一维光晶格的组合势中的玻色凝聚气体,文章基于平均场G-P方程并运用传播子方法,求解玻色凝聚气体基态波函数及其随时间的演化,给出了物质波干涉图样的空间分布与光晶格势周期结构之间的关系.研究表明,运用这一方法得到的光晶格势中物质波干涉条纹与光学中的多光束干涉相类似,并且与Andrews 和Peil等人的实验结果一致.物质波干涉图样随时间的演化也与Sadhan K. Adhikari通过直接数值求解G-P方程所得结果基本相同.
关键词:
玻色凝聚气体
子凝聚原子云
光晶格势
干涉 相似文献
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Current and space-charge density distribution calculation is of great significance for numerical analysis and design of high-current electron guns and beams. When the electrons’ thermal initial velocities are taken into account, though there have been some numerical methods published, the calculation is very complicated. By introducing equivalent meridional potential and projection trajectory theory, the curvilinear axis trajectory equation for electrons neighboring to a central curved trajectory in rotationally symmetric electro-magnetic fields is derived in first- and second-order approximations. The evolution equation of the current density distribution of toroidal electron sub-beams is derived and it can be used to calculate the current and charge density distribution in electron beams and guns in iteration calculation. A compact numerical algorithm for calculating round high-current electron guns and beams was developed and related program was written as well. As examples, the evolution of the current density distribution of a Pierce gun and a periodic magnetic focusing high-current electron beam is simulated. This proves that this method is effective and practical. 相似文献
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Angel Alastuey 《Journal of statistical physics》1987,48(3-4):839-871
We study the static and dynamic behavior of a classical electron gas in the periodic potential created by an ionic lattice. Using the well-known Vlasov approximation, we derive a mean-field kinetic equation for the density-response function of the electrons. This equation is formally solved in terms of the trajectories of one electron in the mean-field equilibrium potential which determines the local electronic density. The mean-field expressions of the static and dynamic structure factors are then obtained through the fluctuation-dissipation theorem. These expressions are used to show that within the mean-field approximation the system is a conductor at all temperatures and for all dimensions. 相似文献
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D. V. Soldatov 《Moscow University Physics Bulletin》2007,62(4):210-215
A new numerical method is proposed for solving the Cauchy problem for the Schrödinger equation with an asymmetric periodic potential superimposed by a constant electric field. The solution to the Cauchy problem is used to determine the electron’s mean momentum as a function of time, initial conditions, and the applied field. Given an initial state, the mean momentum characterizes the mean current and the conductivity of an asymmetric periodic structure known as the ratchet potential. 相似文献
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V. A. Chuenkov 《Bulletin of the Lebedev Physics Institute》2010,37(10):311-320
An exact solution to the Schrödinger equation for electrons in superlattices with rectangular potential barriers and a periodic potential was obtained. An exact analytical expression for the electromagnetic radiation absorbance during electron intersubband transitions in such superlattices was derived in the first-order perturbation theory with arbitrary parameters. A number of extreme cases were considered. 相似文献
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We analyze an approximate solution to the Dirac equation for an electron in a central potential, in particular, in a Coulomb potential, when Lorentz invariance is violated. A quasi-relativistic approximation for the Dirac equation in an external field has been derived. The directivity pattern of spontaneous emission for a polarized hydrogen atom has been found to be asymmetric. 相似文献
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A. Popa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):575-583
In previous papers we proved that, for stationary systems, the geometric elements of the wave described by the Schrödinger equation, namely the characteristic surfaces and their normals, are periodic solutions of the Hamilton-Jacobi equation. In this paper we prove that the Hamilton-Jacobi equation admits periodic solutions with the same geometrical symmetries as the wave function of the system in the case of the beryllium, boron, carbon and oxygen atoms. The above property is a reflection of the fact that for a multielectron atomic system the energetically most favorable geometric configuration minimizes the electron electron repulsion, and it leads to a general semiclassical calculation method, which is in principle valid for more complex systems. We show that this property can be used to compute the energetic atomic values, with the help of the central field method which we developed in previous publications. The relative error of our method is of the order 3×10-3, compared with experimental data for the atoms mentioned above. The accuracy of our method is revealed by a comparison between our theoretical data and values resulting from Hartree-Fock methods. 相似文献