Hannover 2013 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 50: Atomic systems in external fields II

A 50.7: Vortrag

Freitag, 22. März 2013, 15:30–15:45, B 302

Angular distribution effects in multi-photon ionization — •Gregor Hartmann1,2, Markus Braune3, Toralf Lischke1,2, André Meissner1, André Knie4, Arno Ehresmann4, Markus Ilchen3, Omar Al-Dossary5,6, and Uwe Becker1,2,51Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany — 2Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany — 3DESY Notkestraße 85, 22067 Hamburg, Germany — 4Institut für Physik and CINSaT, Universität Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany — 5Physics Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia — 6National Center for Mathematics and Physics, KACST, Saudi Arabia

The angular distribution of emitted photoelectrons is determined by the transfer of the angular momentum of the ionizing photon to the ejected electron. In the case of two-photon ionization another angular momentum of one comes into play giving rise to a Legendre polynomial of fourth order, the so called β4 term. Interestingly this additional term does not only effect the electrons emitted by two photons but also the one being ejected by one photon only. This shows that both processes are coherently coupled. We show this effect for the first time for the two-photon ionization of the rare gases measured at FLASH. Even more interesting is the fact that this phenomenon is even observed for the case of He although 1s-shell photoionization should exhibit no β4 term at all because the remaining hole is isotropic. We interpret this unexpected result as due to autoionizing doubly excited resonances in He.

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