Mechanisms of Photo Double Ioniztion of Helium by 530 eV Photons

A. Knapp, Th. Weber, S. Schoessler, T. Jahnke, J. Nickles, S. Kammer, O. Jagutzki, L. Ph. Schmidt, H. Schmidt-Boecking, R. Doerner
(Inst. fuer Kernphysik, U. Frankfurt)

A. Kheifets
(Australian Nat. U.)

I. Bray
(Murdoch U.)

A.L. Landers
(Western Michigan U.)

T. Osipov, C.L. Cocke
(Kansas State Univ.)

J. Roesch, M.H. Prior
(Lawrence Berkeley Nat. Lab.)

We have measured fully differential cross sections for photo double ionization of helium 450 eV above the threshold, and where one electron has less than 50 eV kinetic energy, at the LBNL ALS. We found an extremely asymmetric energy sharing distribution between the photo electrons and angular asymmetry parameters β ∼ 2 and β ∼ 0 for the fast and slow electrons, respectively. The electron angular distributions show a dominance of the shake-off mechanism for 2 eV electrons and clear evidence of an inelastic electron-electron scattering at 30 eV (lower energy electron). The measurements and CCC calculations are in excellent agreement.

This work was supported by the Chemical Sciences, Geosciences and Biosciences Division,
Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

Also supported by BMBF and DGF.

Submitted to DAMOP 2002, May 2002 in Williamsburg, VA.

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