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

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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.