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Double ionization of multi-electron atoms exposed to intense femtosecond laser pulses.

机译：暴露于强飞秒激光脉冲的多电子原子的双电离。

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摘要

Atoms exposed to high-intensity femtosecond laser pulses have double-ionization rates many times larger than any theory of independently ionizing electrons predicted. This non-sequential or (“excess”) double ionization has appeared in a number of experiments using a wide range of different atoms and molecules. Unlike most strong-field processes, non-sequential double ionization diminishes in magnitude as the intensity of the incident laser field approaches the intensity of the Coulomb field. In this thesis, numerical simulations examine the time evolution of two-electron atoms in order to understand the physical processes leading to non-sequential double ionization.; The results of simulations which directly solve Schrödinger's equation reveal non-sequential double ionization is the result of a two-step process. In the first step, one electron is pulled from the core, but not necessarily ionized, by the applied laser field. In the second step, this electron revisits the nucleus. Given the appropriate phase of the laser field during this revisit, two electrons may share energy and escape the Coulomb potential. Once double ionization has occurred, the ionized electron probability density leaves the vicinity of the nucleus, forming double-ionization jets with inter-connected velocities.; This description is notable in its nearly classical description of non-sequential double ionization. To gain further insight, the two-electron Hamiltonian was also modeled classically. Purely classical calculations using large ensembles of two-electron atoms were examined and the same general behavior is seen in both classical and quantum simulations. An analysis of the precise positions and momenta of classical trajectories reveals further information about the energy range of the revisiting electron as well as the timing and energy of outgoing double-ionization jets. Specifically, the revisiting electron is found to return to the nuclear core in opposition to the laser force.
机译：暴露于高强度飞秒激光脉冲的原子的双电离速率比任何独立预测电离电子的理论大很多倍。使用大量不同的原子和分子的许多实验中都出现了这种非顺序或（“过量”）双电离。与大多数强场过程不同，当入射激光场的强度接近库仑场的强度时，非顺序双电离的大小会减小。本文通过数值模拟研究了两个电子原子的时间演化过程，以了解导致非顺序双电离的物理过程。直接解决薛定er方程的仿真结果表明，非连续双电离是两步过程的结果。第一步，通过施加的激光场将一个电子从核中拉出，但不一定将其电离。在第二步中，该电子重新进入原子核。如果在此重新访问期间获得适当的激光场相位，则两个电子可以共享能量并逸出库仑电势。一旦发生了两次电离，电离的电子概率密度就离开原子核附近，形成具有相互连接的速度的双电离射流。该描述在其对非顺序双电离的近乎经典的描述中是值得注意的。为了进一步了解，还对经典的两电子哈密顿量进行了建模。检验了使用两个电子原子大集合的纯经典计算，并且在经典和量子模拟中都看到了相同的一般行为。对经典轨迹的精确位置和动量的分析揭示了有关重现电子的能量范围以及传出双电离射流的时间和能量的更多信息。具体而言，发现正在重游的电子与激光相反，返回到核芯。

著录项

  • 作者

    Panfili, Raphael Peter.;

  • 作者单位

    The University of Rochester.;

  • 授予单位 The University of Rochester.;
  • 学科 Physics Optics.; Physics Atomic.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 185 p.
  • 总页数 185
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 光学;分子物理学、原子物理学;
  • 关键词

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