Quantitative Untersuchung der Multi-Photon-Ionisation von Edelgas- und Metallatomen mit Freie-Elektronen-Laser-Strahlung in weichen Röntgengebieten

在DESY用于超高强度软X射线的新的自由电子激光(FEL)闪光(汉堡自由电子激光)上，将用离子和电子能谱方法研究稀有气体和自由开壳金属原子的光致电离。特别令人感兴趣的是非线性效应，如顺序、直接和共振的多光子电离过程，以及强场现象，研究的光子能量高于原子电离阈值。我们的目标是更好地理解超高强度的电离电磁辐射与物质之间的相互作用，特别是电子关联的影响。提出的实验的具体方面是它们的定量特征，通过使用校准的设置绝对确定光子数、光斑大小、脉冲持续时间以及因此FEL的辐照度。测量需要聚焦的软X射线自由电子激光光束才能达到高达1017W cm-2的辐照值。闪光灯目前是世界上唯一可以进行这些实验的地方。

At the new Free-Electron Laser (FEL) FLASH (Free-Electron LASer in Hamburg) at DESY for soft X-rays of ultra-high intensity, photoionization of rare gases and free open-shell metal atoms will be studied by means of ion and electron spectroscopy. Of particular interest are non-linear effects such as sequential, direct, and resonant multi-photon ionization processes and strong-field phenomena as well, investigated at photon energies above atomic ionization thresholds. Our aim is a better understanding of the interaction between ionizing electromagnetic radiation of ultra-high intensity and matter in general and, in particular, the influence of electron correlation. Specific aspect of the experiments proposed is their quantitative character by absolute determination of photon number, spot size, pulse duration and, hence, FEL irradiance using a calibrated set-up. The measurements require a focused soft X-ray FEL beam to achieve irradiance values up to 1017 W cm-2. FLASH is currently the only place in the world where those experiments may be performed.