Darmstadt 2008 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 27: Posters: Electron scattering and recombination

A 27.9: Poster

Donnerstag, 13. März 2008, 16:30–18:30, Poster C3

The Coulomb four-body problem: double ionization of helium by electron impact close to threshold — •Xueguang Ren, Alexander Dorn, and Joachim Ullrich — Max-Planck-Institut für Kernphysik, Heidelberg

The dynamics of many-particle quantum systems is still one of the most important unsolved problems in quantum physics. For three-electron escape from an ionic potential close to the fragmentation threshold theories predict a symmetric electron emission with 120° relative angles [1] as well as a T-shape emission with two electrons emitted back-to-back and the third one emitted perpendicular [2]. We have realized such a strongly correlated three electron continuum in electron impact double ionization of helium atoms. Kinematical complete experiments were performed for impact energies 27 eV and 5 eV above the break-up threshold. For the higher energy (27 eV) symmetric as well as T-shape configurations are observed [3]. For 5 eV excess energy only symmetric electron emission is found strongly supporting the Wannier-like saddle point dynamics on which Klar and Schlecht base their work [1].

[1] H. Klar and W. Schlecht, J. Phys. B 9, 1699 (1976)

[2] A. Emmanouilidou and J. M. Rost, J. Phys. B 39, 4037 (2006)

[3] M. Dürr et al., Phys. Rev. Lett. 98, 193201 (2007).