Reconstruction and control of a time-dependent two-electron wave packet
Reconstruction and control of a time-dependent two-electron wave packet
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DOI：
10.1038/nature14026
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发表时间：
2014-12-18
期刊：
影响因子：
64.8
通讯作者：
Pfeifer, Thomas
中科院分区：
文献类型：
--
作者：
Ott, Christian;Kaldun, Andreas;Pfeifer, Thomas
两个或多个束缚电子的协调运动控制着原子（1）和分子（2，3）的非平衡过程，包括化学反应，因此，在量子体系中对这种电子动力学的详细理解非常感兴趣。然而，量子三体问题没有精确的解，因此即使是两个活跃电子和一个原子核的最小系统也是解析上难以解决的（4）。这使得实验测量两个束缚和相关电子的动力学，如在氦原子中发现的，一个有吸引力的前景。然而，尽管单个活跃电子和空穴的运动已经以阿秒时间分辨率（5-7）观测到，但迄今为止，关于双电子运动的可比实验仍然遥不可及。在这里，我们表明，一个相关的两个电子波包可以重建从1.2飞秒的量子拍之间的低洼的双激发态氦。拍频出现在阿秒瞬态吸收光谱（5，7 -9）中，测量具有前所未有的高光谱分辨率，并且存在强度可调谐的可见激光场。我们通过调节可见光强度来调节两个低能级之间的耦合（10-12），并利用Fano共振作为相敏量子干涉仪（13）来实现对两个关联电子的相干控制。由于与氦原子的大规模量子力学计算非常一致，我们预计我们在这里报告的多维光谱实验将为在更复杂的系统中测试基本的少体量子动力学理论提供基准数据。它们还可能提供一种途径，用于对处于基本化学反应核心的亚稳电子过渡态进行特定位置的测量和控制。
The concerted motion of two or more bound electrons governs atomic(1) and molecular(2,3) non-equilibrium processes including chemical reactions, and hence there is much interest in developing a detailed understanding of such electron dynamics in the quantum regime. However, there is no exact solution for the quantum three-body problem, and as a result even the minimal system of two active electrons and a nucleus is analytically intractable(4). This makes experimental measurements of the dynamics of two bound and correlated electrons, as found in the helium atom, an attractive prospect. However, although the motion of single active electrons and holes has been observed with attosecond time resolution(5-7), comparable experiments on two-electron motion have so far remained out of reach. Here we show that a correlated two-electron wave packet can be reconstructed from a 1.2-femtosecond quantum beat among low-lying doubly excited states in helium. The beat appears in attosecond transient-absorption spectra(5,7-9) measured with unprecedentedly high spectral resolution and in the presence of an intensity-tunable visible laser field. We tune the coupling(10-12) between the two low-lying quantum states by adjusting the visible laser intensity, and use the Fano resonance as a phase-sensitive quantum interferometer(13) to achieve coherent control of the two correlated electrons. Given the excellent agreement with large-scalequantum-mechanical calculations for the helium atom, we anticipate that multidimensional spectroscopy experiments of the type we report here will provide benchmark data for testing fundamental few-body quantum dynamics theory in more complex systems. They might also provide a route to the site-specific measurement and control of metastable electronic transition states that are at the heart of fundamental chemical reactions.