Ionization of multi-electron atomic and molecular systems driven by intense and ultrashort laser pulses

阿秒（10^（-18）秒）是多电子原子和分子完全电离和分裂期间多电子效应的自然时间尺度。产生超短激光脉冲的最新进展提高了在这个新的时间尺度上研究原子，分子和核物理的可能性，为我们的微观知识和对物质的理解带来了革命。Attoscience的两个迷人的和互补的挑战是确定相关的多电子动力学的基本兴趣，例如，分子成像-在原子和分子系统的物理机制，并设计方案来探测/控制这些机制。这是拟议研究的总体目标。操纵小分子的电子运动将为修改复杂生物分子的结构铺平道路，从而影响物理，化学，生物学和材料科学等不同领域。该问题包括探索由强和超短激光脉冲驱动的复杂原子和分子的相互作用。考虑到计算能力的最新发展，用三维（3-d）第一原理技术（即量子力学技术）解决这个问题是一项艰巨的任务。因此，经典/半经典技术，这是比量子力学的快得多，将有助于探索相关的电子动力学驱动复杂的原子和分子系统。我最近开发的背景下，驱动的双电离氦，一个3-D的经典方法，解决驱动系统的完全分裂。这种技术的优点是它比量子力学处理快得多，并且它解释了库仑奇点-电子在靠近原子中心时经历的无限强大的力。因此，这是一个进步相比，以前的经典研究忽略库仑奇点完全。我打算推广这种准经典方法，并发展一种有效而复杂的数值工具来处理复杂驱动的原子和分子系统的完全碎裂。利用这种三维准经典方法，我将首先解决强激光脉冲驱动的三电子原子中的多电子效应--一个尚未被探索的问题。主要目标之一是探测（时间分辨）当原子与非常弱的场（单光子吸收）相互作用时，三个电子在碎裂过程中逃逸的主要机制/路径。我将使用圆偏振红外超短激光脉冲作为阿秒钟，将从观察到的最后碎片光谱中获得的信息映射到阿秒相关电子动力学。然后，我将继续探索在双电离的相关电子动力学的双活性或双电子双原子分子与移动的核时，强烈的超短激光脉冲驱动。这个问题处于阿托科学的前沿，在理论上还远远没有得到很好的理解。使用不同强度的脉冲，我将能够探索不同的电离机制，并为每个机制探索不同的机制，管理两个电子逃逸，两个原子中心对双电离的影响，以及导致不同最终产品的过程的相互作用。我们的愿景是将这些研究推广到解决具有移动核的驱动三原子分子-一个未探索的问题-并研究分裂几何形状及其对初始分子状态的依赖性。最后，结合我在探测单光子过程和强驱动分子的多电子效应方面的专业知识，我将使用超短激光脉冲的组合来解决驱动多中心分子分裂过程中的时间分辨和控制电子运动。

Attoseconds (10^(-18) sec) are the natural time-scale for multi-electron effects during complete ionization and break-up of multi-electron atoms and molecules. The recent advances in generating ultrashort laser pulses raise the possibility to investigate atomic, molecular, and nuclear physics at this new time-scale, bringing a revolution in our microscopic knowledge and understanding of matter. Two fascinating and complementary challenges of Attoscience are to identify the physical mechanisms underlying the correlated multi-electron dynamics--of fundamental interest to, for instance, molecular imaging--in atomic and molecular systems and to devise schemes to probe/control these mechanisms. This is the overall aim of the proposed research. Steering the electronic motion for manipulating small molecules will pave the way for modifying the structure of complex biomolecules, thus impacting such diverse fields as physics, chemistry, biology and material science. The problem consists of exploring the interaction of complex atoms and molecules driven by intense and ultrashort laser pulses. Given the state of the art in computational capabilities, solving this problem with three-dimensional (3-d) first-principle techniques, namely, quantum mechanical ones, is an immense task. Thus, classical/semiclassical techniques, which are much faster than quantum mechanical ones, will be instrumental in exploring the correlated electron dynamics in driven complex atomic and molecular systems. I recently developed, in the context of the driven double ionization of Helium, a 3-d classical method that addresses the full fragmentation of driven systems. The advantage of this technique is that it is much faster than quantum mechanical treatments and it accounts for the Coulomb singularity--the infinitely strong force an electron experiences when it is close to the atomic center. It is thus a step forward compared to previous classical studies which ignore the Coulomb singularity altogether. I propose to generalize this quasiclassical technique, and develop an efficient and sophisticated numerical tool for the treatmentof the full fragmentation of complex driven atomic and molecular systems.Using this 3-d quasiclassical technique, I will first address multi-electron effects in three electron atoms driven by strong laser pulses--a problem vastly unexplored. One of the main goals is to probe (time-resolve) the main mechanisms/paths the three electrons follow to escape during the fragmentation process when the atom is interacting with a very weak field (single photon absorption). I will do so using a circularly polarized infrared ultrashort laser pulse as an attosecond clock to map the information obtained from the observed spectra of the final fragments to the attosecond correlated electron dynamics. I will then proceed to explore the correlated electron dynamics in the double ionization of two- active or two-electron diatomic molecules with moving nuclei when driven by intense ultrashort laser pulses. This problem is at the forefront of Attoscience and is far from being theoretically well understood. Using pulses of different intensity I will be able to explore different ionization regimes and for each regime explore the different mechanisms that govern the two electron escape, the effect of the two atomic centers on the double ionization, and the interplay of processes that result in different final products. The vision is to generalize these studies to tackle driven triatomic molecules with moving nuclei--an unexplored problem--and study the break-up geometries and their dependence on the initial molecular state. Finally, combining my expertise on probing single photon processes and on multi-electron effects of strongly driven molecules, I will address time-resolving and controlling the electronic motion during the break-up of driven multi-center molecules using combinations of ultrashort laser pulses.