Real-time observation of valence electron motion
Real-time observation of valence electron motion
复制标题
DOI：
10.1038/nature09212
复制
发表时间：
2010-08-05
期刊：
影响因子：
64.8
通讯作者：
Krausz, Ferenc
中科院分区：
文献类型：
--
作者：
Goulielmakis, Eleftherios;Loh, Zhi-Heng;Krausz, Ferenc
量子态的叠加驱动着原子和亚原子尺度上的运动，态的能量间隔决定着运动的速度。对于处于原子和分子外层（价）壳层且能量间隔为电子伏特量级的电子来说，这意味着价电子的运动发生在亚飞秒到几飞秒的时间尺度上（1飞秒 = 10⁻¹⁵秒）。在缺乏完整测量的情况下，运动可以用一个复数量——密度矩阵来表征。在此我们报道了对氪原子离子价电子密度矩阵的阿秒泵浦 - 探测测量结果。我们用一个受控的少周期激光场产生离子，然后通过阿秒极紫外脉冲的光谱分辨吸收来探测它们，这使我们能够实时观察价电子在多飞秒时间跨度内的亚飞秒运动。我们能够完全表征量子力学电子运动，并确定其在系综样本中的相干程度。尽管目前的研究使用的是一个简单的、典型的开放系统，但阿秒瞬态吸收光谱应该适用于分子和固态材料，以揭示控制物理、化学和生物性质及过程的基本电子运动。
The superposition of quantum states drives motion on the atomic and subatomic scales, with the energy spacing of the states dictating the speed of the motion. In the case of electrons residing in the outer (valence) shells of atoms and molecules which are separated by electronvolt energies, this means that valence electron motion occurs on a subfemtosecond to few-femtosecond timescale (1 fs = 10(-15) s). In the absence of complete measurements, the motion can be characterized in terms of a complex quantity, the density matrix. Here we report an attosecond pump-probe measurement of the density matrix of valence electrons in atomic krypton ions(1). We generate the ions with a controlled few-cycle laser field(2) and then probe them through the spectrally resolved absorption of an attosecond extreme-ultraviolet pulse(3), which allows us to observe in real time the subfemtosecond motion of valence electrons over a multifemtosecond time span. We are able to completely characterize the quantum mechanical electron motion and determine its degree of coherence in the specimen of the ensemble. Although the present study uses a simple, prototypical open system, attosecond transient absorption spectroscopy should be applicable to molecules and solid-state materials to reveal the elementary electron motions that control physical, chemical and biological properties and processes.