Electron localization following attosecond molecular photoionization
Electron localization following attosecond molecular photoionization
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DOI：
10.1038/nature09084
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发表时间：
2010-06-10
期刊：
影响因子：
64.8
通讯作者：
Vrakking, M. J. J.
中科院分区：
文献类型：
--
作者：
Sansone, G.;Kelkensberg, F.;Vrakking, M. J. J.
在过去的几十年里，我们已经能够直接探测与化学转变相关的原子运动，并且发生在飞秒（10（-15）-s）时间尺度上。然而，在电子时间尺度上研究原子和分子的内部工作机制（1-4）只有随着孤立的阿秒（10（-18）-s）激光脉冲（5）的最新发展才成为可能。这种脉冲已被用于研究原子光激发和光电离（6，7）和固体中的电子动力学（8），并在分子中可以帮助探索伴随光激发过程的即时电荷重新分布和本地化。在最近的工作中，H（2）和D（2）的解离电离在飞秒时间尺度上被监测（9），并使用几个周期的近红外激光脉冲（10）进行控制。在这里，我们报告了一个分子阿秒泵浦探测实验的基础上的工作：H（2）和D（2）的解离电离的序列包括一个孤立的阿秒紫外脉冲和一个强烈的几个周期的红外脉冲，和一个本地化的分子内的电子电荷分布的测量依赖于阿秒时间分辨率的泵浦和探测脉冲之间的延迟。局域化通过两种机制发生，其中红外激光影响分子离子的光致电离或解离。在第一种情况下，电荷局域化是由涉及自电离态和离开电子的激光改变波函数的量子力学干涉引起的;在第二种情况下，电荷局域化是由于激光驱动的分子离子不同电子态之间的布居转移引起的。这些结果建立阿秒泵探测策略作为一个强大的工具，调查复杂的分子动力学，导致电子和核运动之间的耦合超出通常的玻恩-奥本海默近似。
For the past several decades, we have been able to directly probe the motion of atoms that is associated with chemical transformations and which occurs on the femtosecond (10(-15)-s) timescale. However, studying the inner workings of atoms and molecules on the electronic timescale(1-4) has become possible only with the recent development of isolated attosecond (10(-18)-s) laser pulses(5). Such pulses have been used to investigate atomic photoexcitation and photoionization(6,7) and electron dynamics in solids(8), and in molecules could help explore the prompt charge redistribution and localization that accompany photoexcitation processes. In recent work, the dissociative ionization of H(2) and D(2) was monitored on femtosecond timescales(9) and controlled using few-cycle near-infrared laser pulses(10). Here we report a molecular attosecond pump-probe experiment based on that work: H(2) and D(2) are dissociatively ionized by a sequence comprising an isolated attosecond ultraviolet pulse and an intense few-cycle infrared pulse, and a localization of the electronic charge distribution within the molecule is measured that depends-with attosecond time resolution-on the delay between the pump and probe pulses. The localization occurs by means of two mechanisms, where the infrared laser influences the photoionization or the dissociation of the molecular ion. In the first case, charge localization arises from quantum mechanical interference involving autoionizing states and the laser-altered wavefunction of the departing electron. In the second case, charge localization arises owing to laser-driven population transfer between different electronic states of the molecular ion. These results establish attosecond pump-probe strategies as a powerful tool for investigating the complex molecular dynamics that result from the coupling between electronic and nuclear motions beyond the usual Born-Oppenheimer approximation.