阈上 过程中光电子角分布的精细结构

应用非微扰散射理论并考虑自发辐射，研究了阈上电离过程中光电子的角分布。由于自发辐射的影响，电子的角分布具有精细结构，成功地解释了Nandor等人的实验观测。     

阈上电离过程中光电子的角分布及其精细结构

应用非微扰散射理论研究了阈上电离后光电子的角分布,阐明了光电子角分布的精细结构的产生和演化规律,并澄清了对精细结构的不正确的解释.研究表明,光电子角分布的精细结构由复合贝塞儿函数的振荡产生,其中喷射结构的数目为自变量最大值范围内复合贝塞儿函数极值数的两倍;并指出光电子角分布存在尺度定律,该定律确立了激光强度、频率及原子结构能与光电子角分布的关系.这一研究成功解释了若干实验观测.     

强激光场阈上电离理论

本文提出一种统一的阈上电离理论。根据该理论,可以定量描述较真实的原子阈上电离过程并能清楚地阐明实验观测的阈上电离现象。该现象可理解为前后相继的两个过程:(1)先从无场的初态吸收N个光子而到场缀末态的量子跃迁过程。(2)欲定量描述实验测量,还需考虑光电子逃离光场时与光场相互作用的“后作用效应”。该“后作用效应”是由非均匀激光场所形成的无质动力所引起的经典物理过程。 关键词：     

包含自电离过程的阈上离化

多电子原子都存在自电离过程,本文研究了存在自电离时的阈上离化过程,利用一个简化模型得到了光电子谱的解析表达式。结果表明,自电离的存在使阈上离化过程更为复杂,导致许多新现象的产生。 关键词：     

线偏振双色激光场中氪原子的阈上电离现象

采用基于Guo,Aberg和Crasemann发展的强激光场中的非微扰量子散射理论(GAC理论),研究了线偏振双色激光场中氪(Kr)原子阈上电离的光电子角分布,双色激光场由一系列相同的单周期激光脉冲组成.研究发现光电子角分布有强烈的位相依赖关系,且呈现出反演不对称性、喷射结构和展宽结构等现象,这为实验上通过改变双色激光场的相对相位来观察和控制光电子角分布提供了一种有效的方法.     

阈上电离与高次谐波

通过数值求解一维含时薛定锷方程，研究阈上电离与高次谐波随激光强度的变化关系，结果表明，两者具有相同的特性，都具有平台区和截止位置，但两者又有差别，较低激光强度作用下，谐波谱有平台而光电了能谱为单调下降的，激光强度较高时，两者都平台，对应的平台区和截止位置相同。     

原子势对阈上电离平台的影响

本文从理论上分别研究了长程和短程原子势对阈上电离光电子谱平台结构的影响. 发现在相当大的激光参数范围内, 长程势的阈上电离谱总是呈现出清晰的双平台结构; 对于短程势, 阈上电离谱双平台的界限不再清晰, 随着入射激光强度的减小, 逐渐从双平台过渡到单平台. 基于经典分析和量子力学数值模拟, 阐明了在不同模型势下, 电离速率的差别和再散射电子弹性碰撞截面的不同导致了上述平台结构的差异．此外, 还讨论了激光脉冲空间强度分布对这一现象的影响. 关键词： 阈上电离 离子势影响 中红外激光脉冲     

Ar原子序列双光双电离产生光电子角分布的理论计算

基于多组态Dirc-Fock方法和密度矩阵理论,给出了原子序列双光双电离光电子角分布的计算表达式,发展了相应的计算程序.利用该程序对Ar原子3p壳层序列双光双电离过程进行了理论研究,给出了光电离的总截面、磁截面、剩余离子取向以及光电子角分布的各向异性参数与入射光子能量的函数关系.结果显示在光电离截面的Cooper极小位置附近取向参数出现极大值,而光电子角分布的各向异性参数在该位置附近出现极小值.进一步给出了33.94和55.34 eV光子能量下序列双光双电离过程中第一步的Ar原子和第二步的Ar^+离子3p壳层光电子角分布,分析了序列双光双电离光电子角分布与单光电离光电子角分布的差异.将计算结果与文献已有的数据进行了比较,具有很好的一致性.本文的研究结果对揭示光与物质相互作用的非线性动力学机制具有重要的参考价值.     

氢原子在红外激光和极紫外脉冲组合场中的阈上电离

通过求解氢原子在强红外(IR)激光和极紫外（XUV）脉冲组合场中的三维含时薛定谔方程(TDSE),理论研究了XUV脉冲的加入对光电子能谱和二维光电子动量分布的影响.计算结果表明,与仅由红外场驱动的情况相比,组合场驱动下的光电子能谱和二维光电子动量分布中呈现出明显的干涉增强结构,干涉结构对XUV脉冲的强度、光子能量和时间延迟都有很强的依赖,该方案可实现高能阈上电离谱的选择性增强.     

Low-energy structure in the ionization of argon: Comparison of experiment with theory

The above-threshold ionization of argon in an intense 70-fs,400-nm linearly polarized laser pulse has been investigated by the velocity map imaging techniques,combined with an attosecond-resolution quantum wave packet dynamics method.There is a quantitative agreement in all dominant features between the experiment and the theory.Moreover,a peak-splitting phenomenon in the first energy peak has been observed at high pulse intensity.Further,through the theoretical analysis,an ac Stark splitting with evident resonant and nonresonant ionization pathways has been found to be the physical reason for the experimental observations.     

Investigation on the influence of atomic potentials on the above threshold ionization

We systematically investigate the influence of atomic potentials on the above-threshold ionization （ATI） spectra in one-dimensional （1D） cases and compare them with the three-dimensional （3D） case by numerically solving the time-dependent Schrrdinger equation. It is found that the direct ionization plateau and the rescattering plateau of the ATI spectrum in the 3D case can be well reproduced by the 1D ATI spectra calculated from the supersolid-core potential and the soft-core potential, respectively. By analyzing the factors that affect the yield of the ATI spectrum, we propose a modified-potential with which we can reproduce the overall 3D ATI spectrum. In addition, the influence of the incident laser intensities and frequencies on the ATI spectra calculated from the proposed modified potential is studied.     

多通道光离化的光电子干涉效应及空间角分布

利用光电子角分布成像光谱技术原理,以钠原子为例利用双光子共振三光子电离方法研究了从钠原子的4D态双能级电离后所产生的光电子角分布的状态.分析、讨论了多通道电离过程中所产生光电子的干涉效应.分析了光电子的空间角分布各部分的物理意义.结果表明该干涉图谱能够清楚地描绘出光电子能量和空间角分布状态.     

原子激发态在高频强激光作用下的光电离研究

本文通过数值求解动量空间的三维含时薛定谔方程, 研究了原子高激发态在高频激光脉冲作用下, 在电离阈值附近的光电子能谱和两维动量角分布. 研究结果表明: 在该能量范围内, 单光子电离过程的贡献是最主要的. 体系初态的主量子数可以由光电子能谱峰值的位置来确定; 体系初态的角量子数可以通过光电子的两维动量角度分布确定. 在比较宽泛的参数范围内, 这一规律不随入射激光的强度和脉冲时间宽度的改变而改变, 因此原则上可以利用它对原子的初态进行识别. 此外, 还研究了体系的初态为相干叠加态, 光电子动量谱随着叠加态相对相位的变化规律. 关键词： 阈上电离 激发态 高频激光脉冲 两维动量角度分布     

Investigation of Angular Dependence of Strong-Field Tunneling Ionization for Asymmetric Diatomic Molecule HeH~(2+)

We determine the structure parameters for the asymmetric heteronuclear diatomic molecule HeH 2+ at several internuclear distances with the molecular wavefunctions obtained by solving the time-independent Schr¨odinger equation with B-spline basis.Then the angular dependence of strong-field ionization rates of HeH 2+ are investigated with the molecular tunneling ionization theory.We show that the shape of several lowly excited states(i.e.2pσ,2pπ,3dδ) for HeH 2+ are reflected in the orientation dependent ionization rates very well,however,the angle-dependent ionization rate fails to follow the angular distribution of the asymptotic electron density for the ground state 1sσ.We also show that the internuclear distance dependent ionization probabilities are in a good agreement with the more accurate result obtained from the numerical solution of the time-dependent Schro¨dinger equation.     

Investigation of Angular Dependence of Strong-Field Tunneling Ionization for Asymmetric Diatomic Molecule HeH2+

We determine the structure parameters for the asymmetric heteronuclear diatomic molecule HeH²⁺ at several internuclear distances with the molecular wavefunctions obtained by solving the time-independent Schrödinger equation with B-spline basis. Then the angular dependence of strong-field ionization rates of HeH²⁺ are investigated with the molecular tunneling ionization theory. We show that the shape of several lowly excited states (i.e. 2pσ ,2pπ ,3dδ ) for HeH²⁺ are reflected in the orientation dependent ionization rates very well, however, the angle-dependent ionization rate fails to follow the angular distribution of the asymptotic electron density for the ground state 1sσ . We also show that the internuclear distance dependent ionization probabilities are in a good agreement with the more accurate result obtained from the numerical solution of the time-dependent Schrödinger equation.     

Angular Velocity Distribution of the Electric Microfield in Plasma

In theory of the spectral line shapes, the conventional scheme use two approximations for the local electric field (microfield) due to all charged particles of the plasma. The quasi‐static approximations for the ions and the impact approximation for the electrons. The first approximation consists to say that the electric field is constant during the characteristic time. In this work we shall transpose the idea of the first approximation, to the angular velocity of the microfield whereas its strength is kept constant and equal to its mean value. We shall use the Holtsmark approach and the independent particles model (due to Margeneau and Lewis) to compute the static distribution function of the angular velocity of the microfield. In the first approach (Holtsmark), the distribution shows a Lorentzian behavior, whereas the second approach (Margenau and Lewis) shows a gaussian behavior. Subsequently, we have applied the obtained static distribution to show the effect on the broadening of Lyman‐alpha line for a plasma composed of He⁺ ions. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

强光场中原子的电离速率

以静态场隧道电离为基础,在准静态近似的条件下,对描述强光场中原子及其各阶离子电离的电离速率进行了较为系统的总结,纠正了早期对隧道电离的电离速率公式进行讨论并且后来的计算中被广泛引用的文献「１０」中公式的错误,地部分稀有气体原子及其各了子在线偏振、圆偏振强光场中的了速度及相应的阈值光强进行了比较。     

19F+27Al反应产物的角分布、角分散与耗散机制

完成了114MeV¹⁹F+²⁷Al深部非弹性碰撞产物的角分布测量.分析了反应产物B,C,N,O,F,Ne,Na,Mg和Al的实验室系角分布,讨论了反应形成的中间双核系统随时间演化过程中角分布所表现出的耗散特点.从实验上提取了反应产物各元素的角分散参数并作了角分散参数的理论拟合,讨论了角分散参数的物理意义以及角分散参数与耗散反应产物的电荷数Z之间的依赖关系.