Ionization and Relaxation Dynamics of Hydrogen Nanoplasmas: Compiling the full picture

该实验项目旨在全面解决氢纳米液滴暴露于强光激光场时爆炸的时空电子和离子动力学，包括它们的相互联系。就我们最近在原子氦纳米等离子体动力学方面的工作而言，分子靶组成是一个新的方面，甚至可能与脉冲中子源和质子加速等应用相关。目的是利用时间分辨光谱学来解决H和H$_2$在等离子体发展的不同阶段的贡献。超快动力学和等离子体弛豫研究的重点是(i)集体和相干效应对能量吸收、离子充电和电子加速的作用，（ii）等离子体后期电子-离子复合和随后的相关衰变。由于电子发射中的特征特征，时间分辨光谱能够使用两种新开发的诊断方法实时解决等离子体电位在末相的发展，即阻碍俄歇发射和瞬态阈值以上电离。该项目的长远目标将在第一阶段通过目标制备（液滴尺寸，杂质掺杂）和激光条件调整初始性质来实现，这使我们能够实现各种纳米等离子体条件。场景范围从准中性到完全电离的纳米等离子体，并包括一个泵-探针设置，以优化充电过程。诊断被使用，它允许确定电荷状态分解离子反冲能量和记录角分解电子能谱。此外，泵浦探测技术的应用提供了库仑爆炸的表征，并使用双色激光场和相敏光谱，对纳米等离子体的所有周期（即从飞秒到纳秒时间尺度）的电子动力学进行了阿秒分辨率的分析。最后，得到了氢纳米液滴库仑爆炸的全貌。此外，该项目缩小了原子、分子和等离子体的阿秒实验之间的差距。

The experimental project aims to comprehensively resolve the temporal and spatialelectron and ion dynamics of exploding hydrogen nanodroplets including their mutual link upon exposure to strong optical laser fields. With respect to our recent work on nanoplasma dynamics of atomic helium, the molecular target composition is a new aspect which could even be relevant for applications like pulsed neutron sources and proton acceleration. An objective will thus to resolve the contributions of H and H$_2$ in the different phases of the plasma development with the help of time-resolved spectroscopy. The focus of the studies on ultrafast dynamics and plasma relaxation are (i) the role of collective and coherent effects on energy absorption, ion charging and electron acceleration, (ii) electron-ion recombination and subsequent correlated decay in the late plasma period. Due to characteristic signatures in the electron emission, time-resolved spectroscopy enables to resolve the development of the plasma potential in the final phase in real time using two newly developed diagnostic methods, i.e. impeded Auger emission and transient above threshold ionization.The far-reaching objectives of the project will in the first stage be achieved by adjusting the initial properties via target preparation (droplet size, impurity doping) and laser conditions, which allows us to implement a variety of nanoplasma conditions. The scenarios range from quasi-neutral to fully ionized nanoplasmas and includes a pump-probe setup to optimize the charging process. Diagnostics are used, which allow to determine charge state resolved ion recoil energies and record angular-resolved electron spectra. Further, the application of the pump-probe technique provides a characterization of the Coulomb explosion and, using two-color laser fields and phase-sensitive spectroscopy, an attosecond-resolved analysis of the electron dynamics at all periods of the nanoplasma, i.e. from the femtosecond to the nanosecond time scale. Finally, a comprehensive picture of the Coulomb explosion of hydrogen nanodroplets will be obtained. In addition, the project closes the gap between attosecond experiments on atoms, molecules and plasmas.