Max-Planck-Institut für Kernphysik Heidelberg


Collisions of electrons and positrons with atoms and molecules

Priv.-Doz. Dr. Alexander Dorn and Dr. Claus-Dieter Schröter

  Research topics:  |  Ions in Traps  |  Electrons in Collisions  |  Lasers in Time  |  
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Ionization of atoms, molecules and clusters in free electron laser light and in collisions with electrons and positrons

We are studying ionization of atoms or molecules in the brillant light of a free electron laser (FEL) or in collisions with electrons and positrons applying the experimental technique of the reaction microscope. Due to the high efficiency of this multi-particle spectrometer so far unfeasible studies e.g. for electron collisions in the energy range from a few eV (electron volts) up to several keV can be performed. Thus, on one hand, the dynamics of very fundamental few-body Coulomb systems can be explored and, on the other hand, detailed information on reactions is obtained which play an important role in the upper atmosphere, in natural and technical plasmas and in radiation damage of biological tissue (e.g. DNA strand breaks).

Reaction microscope

The reaction microscope for electron-molecule collisions


Tesla Ebit

Electron/positron collision studies - Single ionization of atoms, molecules and clusters

Electron impact single ionization of atoms is extensively studied with conventional experiments where two electron spectometers are used to detect both outgoing electrons in coincidence. We are investigating the single ionization process applying the new reaction microscope covering the full solid angle for electron emission.



Double Ionization of Helium

Electron collision studies - Double ionization of helium

Electron impact double ionization leads to four free and via the Coulomb interaction strongly correlated particles after the collision. By measuring the momentum vectors of all particles we get insight in the ionization mechanisms and can test theoretical calculations.



MOTSchema-dorn.JPG

Multi-photon ionization of laser trapped lithium at the Free Electron Laser in Hamburg (FLASH)

For the first time the electron and ion imaging technique (Reaction Microscope) is combined with an optical atom trap. The trap delivers a perfectly cold and well localized target enabling high resolution momentum measurements of all charged particles emerging from ionizing reactions.
Our first goal is to study double and triple ionization of the fundamental three-electron system lithium.


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