Kraus Peter M, Wörner Hans Jakob
Department of Chemistry, University of California, Berkeley, California, 94720, USA.
Laboratorium für Physikalische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zürich, Switzerland.
Angew Chem Int Ed Engl. 2018 May 4;57(19):5228-5247. doi: 10.1002/anie.201702759. Epub 2018 Apr 6.
The description of the electronic structure of molecules in terms of molecular orbitals is a highly successful concept in chemistry. However, it commonly fails if the electrons in a molecule are strongly correlated and cannot be treated as independent particles. Electron correlation is essential to understand inner-valence X-ray spectroscopies, it can drive ultrafast charge migration in molecules, and it is responsible for many exotic properties of strongly correlated materials. Time-resolved spectroscopy with attosecond resolution is generally capable of following electronic motion in real time and can thus provide experimental access to electron-correlation-driven phenomena. High-harmonic spectroscopy in particular uses the precisely timed laser-driven recollision of electrons to interrogate the electronic structure and dynamics of the investigated system on a sub-femtosecond timescale. In this Review, the capabilities of high-harmonic spectroscopy to follow electronic motion in molecules are discussed. Both qualitative and quantitative approaches to unraveling the detailed dynamical responses of molecular systems following ionization are presented. A new theoretical formalism for the reconstruction of correlation-driven charge migration is introduced. The importance of electron-ion entanglement and electronic coherence in the reconstruction of attosecond hole dynamics are discussed. These advances make high-harmonic spectroscopy a promising technique to decode fundamental electron correlations and to provide experimental data on the complex manifestations of multi-electron dynamics.
从分子轨道的角度描述分子的电子结构是化学中一个非常成功的概念。然而，如果分子中的电子存在强关联且不能被视为独立粒子，这种方法通常就会失效。电子关联对于理解内价层X射线光谱至关重要，它能驱动分子中的超快电荷迁移，并且是强关联材料许多奇特性质的原因。具有阿秒分辨率的时间分辨光谱通常能够实时跟踪电子运动，从而为电子关联驱动的现象提供实验研究途径。特别是高谐波光谱利用精确计时的激光驱动电子再碰撞，在亚飞秒时间尺度上探测被研究系统的电子结构和动力学。在本综述中，讨论了高谐波光谱跟踪分子中电子运动的能力。介绍了定性和定量方法来揭示分子系统电离后的详细动力学响应。引入了一种用于重建关联驱动电荷迁移的新理论形式。讨论了电子 - 离子纠缠和电子相干在阿秒空穴动力学重建中的重要性。这些进展使高谐波光谱成为一种有前景的技术，可用于解码基本电子关联并提供关于多电子动力学复杂表现的实验数据。
