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Mechanisms of Photo Double Ionization of Helium by 529 eV Photons

Mechanisms of Photo Double Ionization of Helium by 529 eV Photons. Alexandra Knapp Group of R. Dörner and H. Schmidt-Böcking University of Frankfurt, Germany. Double ionization. Energy. 0. 79 eV and higher : single + double ionization. Single ionization. Energy. 0.

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Mechanisms of Photo Double Ionization of Helium by 529 eV Photons

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  1. Mechanisms of Photo Double Ionization of Helium by 529 eV Photons Alexandra Knapp Group of R. Dörner and H. Schmidt-Böcking University of Frankfurt, Germany

  2. Double ionization Energy 0 79 eV and higher: single + double ionization Single ionization Energy 0 25 eV … 79 eV: only single ionization

  3. Shake off

  4. Shake off First electron absorbs photon and removes from the nucleus

  5. Shake off

  6. Shake off Change of the effektiv nuclear charge

  7. Shake off Second electron is in its eigenstate  Only single ionization occurs

  8. Shake off Second electron is NOT in its eigenstate  Shake off

  9. Electron-electron scattering (TS1)

  10. Electron-electron scattering (TS1)

  11. Electron-electron scattering (TS1)

  12. Electron-electron scattering (TS1)

  13. Electron-electron scattering (TS1)

  14. Electron-electron scattering (TS1)

  15. Electron-electron scattering (TS1)

  16. Electron-electron scattering (TS1)

  17. Electron-electron scattering (TS1) 90° (e,2e) like collision between the two electrons

  18. Ratio of double to single ionization (theory) Shake off + TS1 Shake off TS1 Photon energy above the threshold [eV]

  19. COLTRIMS with electric field

  20. COLTRIMS Collecting electrons up to 60 eV with 4  solid angle with a combination of an electric and a magnetic field with electric + magnetic field

  21. Questions • Is the assumption of a two-step model valid? • Energy sharing • Asymmetry parameter • Mechanisms of photo double ionization • Angular distributions

  22. Energy sharing CCC-Calculation A. Kheifets, I. Bray Extreme asymmetric energy sharing

  23. Polynomial fit Asymmetry parameter Fast electron absorbs photon energy and its angular momentum

  24. Polynomial fit Asymmetry parameter Two-step model is valid

  25. Angular distributions Very slow electrons: 2 eV Faster electrons: 30 eV Shake off TS1 CCC-Calculation CCC-Calculation The fast electron (indicated by the red arrow) is fixed into the direction of the polarization

  26. TDCS for Eslow = 2 eV and 30 eV q fast electron (448 eV) q slower electron (2 eV) q slower electron (30 eV) q fast electron (420 eV)

  27. Shake off and TS1 can be seen for all angles q fast electron (448 eV) q slower electron (2 eV) q slower electron (30 eV) q fast electron (420 eV) fast- slow =180° fast- slow =90°

  28. Comparison between experiment and theory q fast electron (448 eV) q slower electron (2 eV) q slower electron (30 eV) q fast electron (420 eV)

  29. Conclusion • TDCS of the DPI of Helium were measured at 450 eV above the threshold • electrons are distinguishable because of the asymmetric energy sharing • =2 for very fast and =0 for very slow electrons • very slow ( 2 eV) electrons: Shake off • slightly faster ( 30 eV) electrons: TS1

  30. University Frankfurt: Kansas State University: LBNL: Western Michigan University: Australian National University Canberra: Murdock University Perth: Reinhard Dörner Horst Schmidt-Böcking Alexandra Knapp Thorsten Weber Sven Schößler Till Jahnke Jürgen Nickles Susanne Kammer Ottmar Jagutzki Lothar Schmidt C. Lewis Cocke Timur Osipov Michael H. Prior Jürgen Rösch Allen Landers Anatoli Kheifets Igor Bray Supported by BMBF, DFG and DOE

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