Threshold phenomena in electron impact ionisation of atoms explored by multi-particle imaging techniques

这里提出的实验研究电子与原子的相互作用，在所有（技术）等离子体中具有决定性的重要性，在放射肿瘤治疗以及材料研究中。目的是提供独特的基准数据（i）关于当前感兴趣的基本问题和（ii）通过充分利用多粒子成像光谱仪（反应显微镜）与高质量光电阴极电子束源相结合，为技术相关的目标：前所未有的动量分辨率和效率的设置将允许探索目标物种氦和锂的阈值双电离。这些反应的全微分截面（FDCS）将首次能够验证四体库仑碎裂的阈值理论。这是一个特别热门的话题，因为与已建立的模型相矛盾，最近的理论工作预测，多电子阈值电离的发射几何结构严重依赖于束缚电子的初始构型，并且对于氦和锂应该是非常不同的。平行地，FDCS应该测量重的、技术相关的原子和分子的单电离，覆盖了大部分的末态动量空间，因此，最终测试理论预测。

The here-proposed experiments investigate the interaction of electrons with atoms, being of decisive importance in all (technical) plasmas, in radiation tumour therapy as well as for materials research. The aim is to provide unique benchmark data (i) concerning fundamental questions of current interest and (ii) for technologically relevant targets by fully exploiting multi-particle imaging spectrometers (reaction microscopes) in combination with a high quality photo-cathode electron beam source: The unprecedented momentum resolution and efficiency of the set-up will allow to explore threshold double ionization for the target species helium and lithium. For the first time fully differential cross sections (FDCS) for these reactions will be able to verify threshold theories for four-body Coulomb fragmentation. This is a particularly hot topic since, in contradiction with well established models, recent theoretical works predict that the emission geometry of multi-electron threshold ionization critically depends on the initial configuration of the bound electrons and should be very different for helium and lithium.In parallel FDCS shall be measured for single ionisation of heavy, technologically relevant atoms and molecules, covering a large part of the final state momentum space, thus, ultimately testing theoretical predictions.