Inter-atomic correlated decay processes in doped helium nanodroplets – probing heterogeneous nanosystems with EUV radiation

该研究项目主要旨在研究纯和掺杂的He纳米液滴在极紫外（EUV）到X射线光谱范围内使用同步加速器和超短激光辐射的原子间相关衰变过程。新的相关衰变过程将被识别和表征，这是由于He的特殊电子结构引起的。（双电子系统，高激发态和高电离能），He纳米液滴的量子流体性质（局部激发的高迁移率），多体相互作用（两个和多体原子间能量和电荷转移），以及异质团簇中物种的奇异组合（He，金属，有机分子，水分子壳等）。这种探索将引导我们对纳米尺度上超流性的基本方面有更深入的理解，并阐明几何效应（体与表面）在异质纳米结构光动力学中的作用。特别是，一般的光物理过程的纳米尺寸的掺杂的他nanodrodles，如nanosolvation的中性和阳离子与受激物种和阴离子的驱逐将被阐明。这些研究将有助于理解定制纳米系统和有机材料中的辐射损伤，并为解释最近和即将到来的自由电子激光（FEL）实验提供概念和参考数据。这些目标将通过系统地研究各种系统（各种尺寸和组成的纯和掺杂的He纳米液滴，Ne簇）来实现，使用不同的实验检测技术，如具有速度图成像（VMI）能力的光电子-光离子符合检测（PEPICO）技术以及EUV和可见荧光检测方法。这项拟议的实验工作将在不同的地点进行，例如奥胡斯大学ASTRID 2同步辐射设施的AMO光束线、汉堡FLASH的自由电子激光和的里雅斯特的Fermi@Elettra。

This research project mainly aims at studying inter-atomic correlated decay processes in pure and doped He nanodroplets in the extreme-ultraviolet (EUV) up to the X-ray spectral ranges using synchrotron and ultrashort laser radiation. Novel correlated decay processes will be identified and characterized, which arise from the particular electronic structure of He (two-electron system, high-lying excited states and high ionization energy), the quantum fluid nature of He nanodroplets (high mobility of localized excitations), many-body interactions (two and many-body interatomic energy and charge transfer), and exotic combinations of species in hetero-clusters (He, metals, organic molecules, shells of water molecules, etc.). This quest will lead us toward a deeper understanding of the fundamental aspects of superfluidity on the nanoscale, and elucidate the role of geometric effects (bulk vs. surface) in the photodynamics of heterogeneous nanostructures. In particular, generic photo-physical processes of nanometer-sized doped He nanodroplets such as nanosolvation of neutrals and cations vs. expulsion of excited species and anions will be elucidated. These studies will contribute to the understanding of radiation damage in tailored nano-systems and in organic materials, as well as provide concepts and reference data for interpreting recent and upcoming Free-electron laser (FEL) experiments. These goals will be pursued by systematically investigating various systems (pure and doped He nanodroplets of various sizes and composition, Ne clusters), using different experimental detection techniques such as photoelectron-photoion coincidence detection (PEPICO) technique with velocity-map imaging (VMI) capability and EUV and visible fluorescence detection method. This proposed experimental work will be carried out at various locations, e.g. the AMO beamline of ASTRID2 synchrotron radiation facility at Aarhus University, FEL at FLASH in Hamburg and Fermi@Elettra in Trieste.