激光方脉冲作用下强场自电离过程

本文研究了激光方脉冲作用下的强场自电离过程,从而推广了以往包含高阶离化的研究,讨论了基态布居和自电离共振线型在强场下受激光脉宽、光强的影响。结果表明,强场自电离过程及其中的高阶离化不仅与光强有关,而且还和原子与激光相互作用的时间紧密相关。     

高阶离化对强激光场诱导自电离的影响

本文讨论了以往强激光诱导自电离理论所忽略的二阶以上的高阶离化效应,得到了自电离谱的解析表达式,详细研究了高阶离化的影响。结果表明,当激光场足够强时,高阶离化使自电离谱和自电离态的缀饰态产生显著变化。 关键词：     

强激光场诱导自电离理论

在Fano模型中考虑了在离化限之上额外吸收一个光子的二阶离化过程,重新研究了强激光场诱导自电离的动力学,着重讨论了二阶离化过程对光电子谱的重要影响.     

电场中Eu原子电离阈移动的实验研究

提出了一种新方法, 精确确定了稀土Eu原子第一电离阈的位置. 先用脉冲电场对Eu原子的高激发Rydberg态进行延时场电离探测, 再通过反向静电场排除光电离和自电离等其他路径所产生的离子信号的干扰, 观察并研究了Eu原子第一电离阈随着电场移动的规律. 由此所确定的零场下第一电离阈的数值与采用其他方法所确定的文献值^{[1, 2]}相一致, 从而验证了该方法的可靠性.     

二阶离化对缀饰态稳定性的影响

推广了包含二阶离化和自电离耦合的缀饰态理论,并研究了二阶离化对缀饰态稳定性的影响。结果表明:二阶离化破坏了缀饰态的稳定性,但二阶离化中的C-C耦合在某种程度上可以降低这种不稳定性。 关键词：     

二阶离化过程对双光子自电离光电子能谱的影响

本文研究包含二阶离化过程的双光子自电离;计算光电子能谱,并着重分析二阶离化对光电子能谱及其随光强变化关系的影响。 关键词：     

离化态铁原子光电离截面研究

根据原子自洽场理论,我们对各种离化态铁原子的光电离截面进行了非相对论性和相对论性的理论计算,总结了离化态铁的光电离截面随离化度变化的规律,并讨论了光电离过程的相对论效应。 关键词：     

强激光场下的双光子自电离理论

本文研究了包括二阶离化过程的强激光场下的双光子自电离。导出了光电子谱的解析表达式,并对一些特殊情况下的光电子谱进行了分析。     

光场电离气体原子体系的剩余电子能量

总结并推导了在考虑激光脉冲包络时超短强激光脉冲光场电离多电子气体原子体系的阈上电离能量的计算公式,消除了以往研究中的唯象假设。发展了产生各阶离化态离子的阈值光强和饱和光强的计算方法。数值模拟表明,随激光能量升高,平均剩余电子能量呈现出类似阶梯型平台的饱和行为。     

平滑激光脉冲诱导的阈上离化

阈上离化(above-threshold ionization)是近年来发现的一种新现象。本文在基本态模型基础上利用非微扰理论研究了高斯型激光脉冲诱导的阈上离化,讨论了其特征光电子能谱随时间的演化。 关键词：     

Relativistic nonperturbative above-threshold phenomena in strong laser fields

Relativistic features of various nonperturbative above-threshold phenomena in strong laser fields are discussed and compared. This includes above-threshold ionization of multiply charged ions as well as pair production in an ultrastrong laser wave, superimposed with either a nuclear Coulomb field or another counterpropagating laser wave. For the probability of above-threshold pair production, a new scaling relation is given. Particular attention is paid to similarities among these processes, regarding the energy and angular spectra of the particles as well as the total reaction rates.     

The role of incoherent scattering in laser-induced and laser-assisted processes

We use the S-matrix formalism in order to investigate the possible role of incoherent scattering in different processes in a strong laser field. In the cases of above-threshold ionization (ATI) of atoms and above-threshold detachment (ATD) of negative ions, we assume that the ionized (detached) electron may scatter off a target other than its parent ion (atom). We call such a process incoherent in order to distinguish it from the coherent rescattering of an ionized (detached) electron off its parent ion (atom) which occurs in high-order above-threshold ionization (HATI) and high-order above-threshold detachment (HATD) processes. The same line of reasoning can be applied to the laser-assisted processes, such as the laser-assisted electron-ion radiative recombination (LAR) and the laser-assisted electron-atom scattering (LAS). If the density of the ionic beam used in a LAR experiment is high, it is possible that the electron scatters off an ionic target and subsequently recombines with another ion. Analogously, the electron that scatters on an atom in the LAS process may scatter once more off another atom. We show that the contribution of these incoherent processes to the energy spectra can be higher than that of the corresponding coherent processes if the density of atomic (ionic) targets is high enough. The spectra of the incoherent processes have a cutoff-like behavior and the cutoff energies are higher than those of the corresponding coherent processes. These results are explained by semiclassical analysis.     

Double-hump resonance structure of the cross sections for electron impact ionization of Ar5+

Configuration-average distorted-wave calculations are carried out for electron-impact ionization of Ar5+. Both direct ionization and the indirect excitation autoionization processes are included in our calculations. Our theoretical values are in quite reasonable agreement with the experimental data. The indirect processes contribute up to 50% to the total ionization cross sections. The possible origin of double-hump resonance structure of the cross sections is demonstrated and the contributions of metastable states are also taken into account.     

Method for calculating multiphoton above-threshold processes in atoms: Two-photon above-threshold ionization

The two-photon above-threshold ionization of atoms is calculated using numerical algorithms of the Padé approximation in the model-potential method with the Coulomb asymptotics. The total and differential cross sections of the above-threshold ionization of helium and alkali metal atoms by elliptically polarized radiation are presented. The dependence of the angular distribution of photoelectrons on the sign of the ellipticity of radiation (the elliptic dichroism phenomenon) is analyzed in the above-threshold frequency range.     

Above-threshold ionization of xenon by intense laser field

Above-threshold ionization of xenon atom is treated by the KFR theory withconsideration of screening effects in the initial state.Comparison is made with experiment us-ing circularly polarized laser, screening effects on the above-threshold ionization is also dis-cussed.Better agreement with experiment is found than the previous results using hydrogenicwavefunction.