Institut für Optik und Atomare Physik, Technische Universität Berlin, Strasse des 17. Juni 135, ER 1-1, 10623 Berlin, Germany.
Max-Born-Institut, Max-Born-Straße 2a, 12489 Berlin, Germany.
Sci Rep. 2017 Jan 18;7:40736. doi: 10.1038/srep40736.
Irradiation of nanoscale clusters and large molecules with intense laser pulses transforms them into highly-excited non- equilibrium states. The dynamics of intense laser-cluster interaction is encoded in electron kinetic energy spectra, which contain signatures of direct photoelectron emission as well as emission of thermalized nanoplasma electrons. In this work we report on a so far not observed spectrally narrow bound state signature in the electron kinetic energy spectra from mixed Xe core - Ar shell clusters ionized by intense extreme-ultraviolet (XUV) pulses from a free-electron-laser. This signature is attributed to the correlated electronic decay (CED) process, in which an excited atom relaxes and the excess energy is used to ionize the same or another excited atom or a nanoplasma electron. By applying the terahertz field streaking principle we demonstrate that CED-electrons are emitted at least a few picoseconds after the ionizing XUV pulse has ended. Following the recent finding of CED in clusters ionized by intense near-infrared laser pulses, our observation of CED in the XUV range suggests that this process is of general relevance for the relaxation dynamics in laser produced nanoplasmas.
用强激光脉冲辐照纳米团簇和大分子，将它们转化为高度激发的非平衡态。强激光-团簇相互作用的动力学编码在电子动能谱中，其中包含直接光电子发射以及热化纳米等离子体电子发射的特征。在这项工作中，我们报告了一个迄今为止在由自由电子激光产生的强极端紫外（XUV）脉冲电离的混合 Xe 核 - Ar 壳团簇的电子动能谱中观察到的谱线很窄的束缚态特征。该特征归因于相关电子退激发（CED）过程，其中一个激发原子弛豫，多余的能量用于电离相同或另一个激发原子或纳米等离子体电子。通过应用太赫兹场条纹原理，我们证明 CED 电子是在电离 XUV 脉冲结束后至少几皮秒发射的。在最近发现强近红外激光脉冲电离的团簇中存在 CED 之后，我们在 XUV 范围内观察到 CED 表明，该过程对于激光产生的纳米等离子体的弛豫动力学具有普遍意义。
