Abstract Recent developments yielding intense and short light pulses in the atto-second regime makes it possible to address fundamental questions on the time evolution of the electron dynamics. We demonstrate in our studies that electron pair emission from surfaces holds the promise to unravel the time scale of correlated electron dynamics. This can be achieved without atto-second light sources. We will discuss two different approaches. First we studied the Auger decay following the emission of a core-electron due to photon absorption. With coincidence spectroscopy, we demonstrate an extensive energy sharing between the Ag 4p photoelectron and the NVV Auger electron exceeding 10 eV. This result is at odds with a sequential emission of first the photoelectron and then the Auger electron. This energy width of the sharing provides access to the time scale of the emission process. We convert this to a timescale of 60 as over which the fluctuations takes place. This value is fair agreement with the theoretical calculation of the timescale to fill an exchange-correlation hole. In a second study we utilized the neutralization of ions near a surface. This is known to be efficient process and leads to electron emission via Auger-type processes. Specifically, the neutralization of He2+ ions makes available the double ionization energy. We demonstrate that the neutralization of a single He2+ ion near an Ir(100) surface leads to the emission of an electron pair. Via coincidence spectroscopy we give evidence that a sizable amount of these electron pairs originate from a correlated single step neutralization of the ion involving a total of 4 electrons from the metal. These correlated electron pairs cannot be explained in the common picture of two consecutive and independent neutralization steps. We infer a characteristic time scale for the correlated electron dynamics in the metal of 40–400 as.

中文翻译：

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关于相关电子动力学的时间尺度

摘要 在阿秒范围内产生强和短光脉冲的最新发展使得解决有关电子动力学时间演化的基本问题成为可能。我们在研究中证明，来自表面的电子对发射有望解开相关电子动力学的时间尺度。这可以在没有阿托秒光源的情况下实现。我们将讨论两种不同的方法。首先，我们研究了由于光子吸收导致核电子发射后的俄歇衰变。通过符合光谱，我们证明了 Ag 4p 光电子和超过 10 eV 的 NVV 俄歇电子之间的广泛能量共享。这个结果与先是光电子然后是俄歇电子的顺序发射不一致。这种共享的能量宽度提供了对排放过程时间尺度的访问。我们将其转换为 60 的时间尺度，作为波动发生的时间尺度。该值与填补交换相关漏洞的时间尺度的理论计算相当吻合。在第二项研究中，我们利用了表面附近离子的中和作用。众所周知，这是一种有效的过程，并通过俄歇型过程导致电子发射。具体而言，He2+ 离子的中和使双电离能可用。我们证明了靠近 Ir(100) 表面的单个 He2+ 离子的中和会导致电子对的发射。通过巧合光谱，我们提供了大量这些电子对源自相关的单步中和离子的证据，其中包括来自金属的总共 4 个电子。这些相关的电子对不能在两个连续和独立的中和步骤的共同图片中解释。我们推断金属中相关电子动力学的特征时间尺度为 40-400 as。