论文标题
控制氦气中的一致背对背双电离动力学
Control of concerted back-to-back double ionization dynamics in helium
论文作者
论文摘要
双电离（DI）是一个基本过程，尽管它的简单性显然为探测和控制电子运动提供了丰富的机会。即使是最简单的多电源原子，氦气也仍然可以找到新的DI机制。要在田间强度的一阶强度时，强烈的外场将电子以氦气的速度电离，以使它们被弹出相同的方向（前后运动）。对相反方向的弹射（背靠背运动）无法将其描述为第一阶，这使其成为控制的具有挑战性的目标。在这里，我们以（1 + 1）维模型背靠背电离为目标，以解决此挑战并优化该领域。使用四个不同的控制程序进行优化：（1）短时控制，（2）对场基基膨胀的无衍生化优化，（3）Krotov方法，以及（4）对运动的经典方程的控制。所有四个程序都导致了背靠背运动的主导地位。所有获得的场基本上具有相同的两步机制，导致背靠背运动：首先，电子被磁场移动到同一方向。其次，在田地关闭后，核吸引力和电子电子排斥将结合起来，将最终运动变成每个电子的相反方向。通过执行准经典计算，我们确认该机制本质上是经典的。
Double ionization (DI) is a fundamental process that despite its apparent simplicity provides rich opportunities for probing and controlling the electronic motion. Even for the simplest multielectron atom, helium, new DI mechanisms are still being found. To first order in the field strength, a strong external field doubly ionizes the electrons in helium such that they are ejected into the same direction (front-to-back motion). The ejection into opposite directions (back-to-back motion) cannot be described to first order, making it a challenging target for control. Here, we address this challenge and optimize the field with the objective of back-to-back double ionization using a (1 + 1)-dimensional model. The optimization is performed using four different control procedures: (1) short-time control, (2) derivative-free optimization of basis expansions of the field, (3) the Krotov method, and (4) control of the classical equations of motion. All four procedures lead to fields with dominant back-to-back motion. All the fields obtained exploit essentially the same two-step mechanism leading to back-to-back motion: first, the electrons are displaced by the field into the same direction. Second, after the field turns off, the nuclear attraction and the electron-electron repulsion combine to generate the final motion into opposite directions for each electron. By performing quasi-classical calculations, we confirm that this mechanism is essentially classical.
