Osnabrück 2002 – wissenschaftliches Programm
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MO: Molekülphysik
MO 12: Photoionisation I (gemeinsam mit FV Atomphysik)
MO 12.5: Vortrag
Mittwoch, 6. März 2002, 17:30–17:45, HS 15/E10
Evolution of helium double ionization dynamics — •Slobodan Cvejanovic1, Jens Viefhaus1, Marco Wiedenhöft2, Nora Berrah2, and Uwe Becker1 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany — 2Department of Physics, Western Michigan University, Kalamazoo, USA
We present the results from a most detailed study of the effects of energy sharing on the electron triple differential cross sections (TDCS). The experimental results were analyzed using the global parametrization of Cvejanovic and Reddish, to derive the amplitude parameters, including their relative phase shift, directly from our experimental data measured over a large range of excess energies. The derived double photoionization parameters make it possible to calculate all other properties of DPI at the same photon energy, including their circular dichroism. The circular and linear dichroisms in He are different manifestations of the interference effects between the gerade and ungerade amplitudes, jointly described by the phase difference φ. We demonstrate that the asymptotic behavior of this term governs the specific features of the linear and circular dichroisms in a way that one can introduce an ‘intrinsic handedness’ for the DPI process. The comparison between the data sets taken at different photon energies allow us to derive semi-emrirical formulas for the evolution of the dynamical parameters with the photon energy. This represents the first attempt of obtaining the analytical presentation of the general TDCS in helium with an accuracy that is generally compatible with the present-day experimental accuracies.