Abstract
Double ionization of helium by electron impact is studied in a kinematical complete experiment in the threshold regime at 5 eV excess energy. As expected the recoil ion carries the full initial projectile momentum and the emitted electrons’ sum momentum in average is zero. The electron emission is revealed to be completely dominated by the symmetric 120° configuration predicted by many threshold theories but never observed experimentally before. Fully differential cross sections show a more complex structure than expected for a pure threshold collision dynamics.
- Received 8 May 2008
DOI:https://doi.org/10.1103/PhysRevLett.101.093201
©2008 American Physical Society
Synopsis
Playing pool with atoms
Published 2 September 2008
When an atom is bombarded with just enough energy to fully ionize it, how do the electrons and nucleus break apart from each other? Experimentalists are now able to study such a four-body breakup by bombarding a helium atom with an electron.
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