Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 10: Posters Wednesday (Cooling and Trapping, Electron Scattering and Recombination)

A 10.12: Poster

Mittwoch, 4. April 2001, 12:30–15:00, AT3

Electron-Impact Double Ionization of Helium from the Dipolar to the Impulsive Regime — •Alexander Dorn, Claus Dieter Schröter, Robert Moshammer, Bennaceur Najjari, Giorgi Sakheslasvili, and Joachim Ullrich — Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg, Germany

A kinematically complete experiment for double ionization of helium by 2 keV electron impact is performed applying a multi-electron - recoil-ion coincidence technique. A large part of the 12-dimensional, 4-particle final-state momentum space is mapped with sufficient statistics to extract fully differential cross sections. Thus, the collision dynamics can be investigated for kinematics ranging from the optical limit to high momentum transfer up to 5 a.u. and over a large range of relative emission angles as well as energy partitions between the two ejected electrons. A distinct change of the collision dynamics is observed being close to photo-double ionization for small momentum transfer and showing the characteristics of close binary collisions for high momentum transfer. It is demonstrated that electron impact double ionization can be a sensitive tool for investigating the electron correlation in the initial target state.